NuttX RTOS Porting GuideLast Updated: May 12, 2016 |
Table of Contents |
up_initialize()
up_idle()
up_initial_state()
up_create_stack()
up_use_stack()
up_stack_frame()
up_release_stack()
up_unblock_task()
up_block_task()
up_release_pending()
up_reprioritize_rtr()
_exit()
up_assert()
up_schedule_sigaction()
up_allocate_heap()
up_interrupt_context()
up_disable_irq()
up_enable_irq()
up_prioritize_irq()
up_putc()
work_queue()
work_cancel()
work_signal()
work_available()
work_usrstart()
lpwork_boostpriority()
lpwork_restorepriority()
up_addrenv_create()
up_addrenv_destroy()
up_addrenv_vtext()
up_addrenv_vdata()
up_addrenv_heapsize()
up_addrenv_select()
up_addrenv_restore()
up_addrenv_clone()
up_addrenv_attach()
up_addrenv_detach()
up_addrenv_ustackalloc()
up_addrenv_ustackfree()
up_addrenv_vustack()
up_addrenv_ustackselect()
up_addrenv_kstackalloc()
up_addrenv_kstackfree()
boardctl()
Application Interfaceup_testset()
up_cpu_index()
up_cpu_start()
up_cpu_pause()
up_cpu_resume()
os_start()
sched_process_timer()
sched_timer_expiration()
sched_alarm_expiration()
irq_dispatch()
up_shmat()
up_shmdt()
1.0 Introduction |
Overview This document provides and overview of the NuttX build and configuration logic and provides hints for the incorporation of new processor/board architectures into the build.
See also arch/README.txt
and configs/README.txt
.
2.0 Directory Structure |
Directory Structure. The general directly layout for NuttX is very similar to the directory structure of the Linux kernel -- at least at the most superficial layers. At the top level is the main makefile and a series of sub-directories identified below and discussed in the following paragraphs:
. |- nuttx | |-- Makefile | |-- Kconfig | |-- Documentation | | `-- (documentation files)/ | |-- arch/ | | |-- Kconfig | | |-- <arch-name>/ | | | |-- include/ | | | | |--<chip-name>/ | | | | | `-- (chip-specific header files) | | | | |--<other-chips>/ | | | | `-- (architecture-specific header files) | | | `-- src/ | | | |--<chip-name>/ | | | | `-- (chip-specific source files) | | | |--<other-chips>/ | | | `-- (architecture-specific source files) | | `-- <other-architecture directories>/ | |-- audio/ | | |-- Makefile | | |-- Kconfig | | `-- (common audio source files) | |-- binfmt/ | | |-- Makefile | | |-- Kconfig | | |-- (binfmt-specific sub-directories)/ | | | `-- (binfmt-specific source files) | | `-- (common binfmt source files) | |-- configs/ | | |-- <board-name>/ | | | |-- include/ | | | | `-- (other board-specific header files) | | | |-- src/ | | | | `-- (board-specific source files) | | | |---<config-name>/ | | | | `-- (board configuration-specific source files) | | | `---(other configuration sub-directories for this board)/ | | `-- <(other board directories)>/ | |-- drivers/ | | |-- Makefile | | |-- Kconfig | | |-- (driver-specific sub-directories)/ | | | `-- (driver-specific source files) | | `-- (common driver source files) | |-- fs/ | | |-- Makefile | | |-- Kconfig | | |-- (file system-specific sub-directories)/ | | | `-- (file system-specific source files) | | `-- (common file system source files) | |-- graphics/ | | |-- Makefile | | |-- Kconfig | | |-- (feature-specific sub-directories)/ | | | `-- (feature-specific source files library source files) | | `-- (common graphics-related source files) | |-- include/ | | |-- (standard header files) | | |-- (standard include sub-directories) | | | `-- (more standard header files) | | |-- (non-standard include sub-directories) | | `-- (non-standard header files) | |-- libc/ | | |-- Makefile | | |-- Kconfig | | `-- (libc source files) | |-- libxx/ | | |-- Makefile | | |-- Kconfig | | `-- (libxx management source files) | |-- mm/ | | |-- Makefile | | |-- Kconfig | | `-- (memory management source files) | |-- net/ | | |-- Makefile | | |-- Kconfig | | |-- arp/ | | | `-- (ARP source files) | | |-- devif/ | | | `-- (Ethernet device interface source files) | | |-- icmp/ | | | `-- (ICMP source files) | | |-- igmp/ | | | `-- (IGMP source files) | | |-- iob/ | | | `-- (I/O buffering source files) | | |-- ipv6/ | | | `-- (IPv6 source files) | | |-- netdev/ | | | `-- (Socket device interface source files) | | |-- pkt/ | | | `-- (Packet socket source files) | | |-- route/ | | | `-- (Routing table source files) | | |-- socket/ | | | `-- (BSD socket source files) | | |-- tcp/ | | | `-- (TCP source files) | | |-- udp/ | | | `-- (UDP source files) | | `-- utils/ | | `-- (Miscellaneous, utility source files) | |-- sched/ | | |-- Makefile | | |-- Kconfig | | `-- (sched source files) | |-- syscall/ | | |-- Makefile | | |-- Kconfig | | `-- (syscall source files) | |-- tools/ | | `-- (miscellaneous scripts and programs) | `-- tools/ | |-- Makefile | |-- Kconfig | `-- (wireless management source files) `- apps |-- netutils/ | |-- Makefile | |-- Kconfig | |-- (network feature sub-directories)/ | | `-- (network feature source files) | `-- (netutils common files) |-- nshlib/ | |-- Makefile | |-- Kconfig | `-- NuttShell (NSH) files |-- (Board-specific applications)/ | |-- Makefile | |-- Kconfig | |-- (Board-specific application sub-directories)/ | | `-- (Board-specific application source files) | `-- (Board-specific common files) `-- examples/ `-- (example)/ |-- Makefile |-- Kconfig `-- (example source files)
Configuration Files. The NuttX configuration consists of:
arch/
<arch-name>/
directory
and are discussed in a paragraph below.
These chip-specific files are contained within chip-specific sub-directories in the
arch/
<arch-name>/
directory and are selected via
the CONFIG_ARCH_name
selection.
These board-specific configuration files can be found in the
configs/
<board-name>/
sub-directories and are discussed
in a paragraph below.
General documentation for the NuttX OS resides in this directory.
This directory contains several sub-directories, each containing
architecture-specific logic.
The task of porting NuttX to a new processor consists of
add a new subdirectory under arch/
containing logic specific
to the new architecture.
The complete board port in is defined by the architecture-specific code in this
directory (plus the board-specific configurations in the config/
subdirectory).
Each architecture must provide a subdirectory, <arch-name>
under arch/
with the following characteristics:
<arch-name>/ |-- include/ | |--<chip-name>/ | | `-- (chip-specific header files) | |--<other-chips>/ | |-- arch.h | |-- irq.h | |-- types.h | |-- limits.h | `-- syscall.h `-- src/ |--<chip-name>/ | `-- (chip-specific source files) |--<other-chips>/ |-- Makefile `-- (architecture-specific source files)
include/
<chip-name>/
This sub-directory contains chip-specific header files.
include/arch.h
:
This is a hook for any architecture specific definitions that may
be needed by the system. It is included by include/nuttx/arch.h
.
include/types.h
:
This provides architecture/toolchain-specific definitions for
standard types. This file should typedef
:
_int8_t, _uint8_t, _int16_t, _uint16_t, _int32_t, _uint32_t_t
and if the architecture supports 24- or 64-bit integers
_int24_t, _uint24_t, int64_t, uint64_t
NOTE that these type names have a leading underscore character. This file will be included(indirectly) by include/stdint.h and typedef'ed to the final name without the underscore character. This roundabout way of doings things allows the stdint.h to be removed from the include/ directory in the event that the user prefers to use the definitions provided by their toolchain header files
And finally
irqstate_t
Must be defined to the be the size required to hold the interrupt enable/disable state.
This file will be included by include/sys/types.h and be made available to all files.
include/irq.h
:
This file needs to define some architecture specific functions (usually
inline if the compiler supports inlining) and some structures. These include:
struct xcptcontext
:
This structures represents the saved context of a thread.
irqstate_t up_irq_save(void)
:
Used to disable all interrupts.
In the case of multi-CPU platforms, this function disables interrupts on CPUs.
void up_irq_restore(irqstate_t flags)
:
Used to restore interrupt enables to the same state as before up_irq_save()
was called.
This file must also define NR_IRQS
, the total number of IRQs supported
by the board.
include/syscall.h
:
This file needs to define some architecture specific functions (usually
inline if the compiler supports inlining) to support software interrupts
or syscalls that can be used all from user-mode applications into
kernel-mode NuttX functions.
This directory must always be provided to prevent compilation errors.
However, it need only contain valid function declarations if the architecture
supports the CONFIG_BUILD_PROTECTED
or CONFIG_BUILD_KERNEL
configurations.
uintptr_t sys_call0(unsigned int nbr)
:
nbr
is one of the system call numbers that can be found in include/sys/syscall.h
.
This function will perform a system call with no (additional) parameters.
uintptr_t sys_call1(unsigned int nbr, uintptr_t parm1)
:
nbr
is one of the system call numbers that can be found in include/sys/syscall.h
.
This function will perform a system call with one (additional) parameter.
uintptr_t sys_call2(unsigned int nbr, uintptr_t parm1, uintptr_t parm2)
:
nbr
is one of the system call numbers that can be found in include/sys/syscall.h
.
This function will perform a system call with two (additional) parameters.
uintptr_t sys_call3(unsigned int nbr, uintptr_t parm1, uintptr_t parm2, uintptr_t parm3)
:
nbr
is one of the system call numbers that can be found in include/sys/syscall.h
.
This function will perform a system call with three (additional) parameters.
uintptr_t sys_call4(unsigned int nbr, uintptr_t parm1, uintptr_t parm2, uintptr_t parm3, uintptr_t parm4)
:
nbr
is one of the system call numbers that can be found in include/sys/syscall.h
.
This function will perform a system call with four (additional) parameters.
uintptr_t sys_call5(unsigned int nbr, uintptr_t parm1, uintptr_t parm2, uintptr_t parm3, uintptr_t parm4, uintptr_t parm5)
:
nbr
is one of the system call numbers that can be found in include/sys/syscall.h
.
This function will perform a system call with five (additional) parameters.
uintptr_t sys_call6(unsigned int nbr, uintptr_t parm1, uintptr_t parm2, uintptr_t parm3, uintptr_t parm4, uintptr_t parm5, uintptr_t parm6)
:
nbr
is one of the system call numbers that can be found in include/sys/syscall.h
.
This function will perform a system call with six (additional) parameters.
This file must also define NR_IRQS
, the total number of IRQs supported
by the board.
src/
<chip-name>/
This sub-directory contains chip-specific source files.
src/Makefile
:
This makefile will be executed to build the targets src/libup.a
and
src/up_head.o
. The up_head.o
file holds the entry point into the system
(power-on reset entry point, for example). It will be used in
the final link with libup.a
and other system archives to generate the
final executable.
include/nuttx/arch.h
identifies all of the APIs that must
be provided by the architecture specific logic. (It also includes
arch/
<arch-name>/arch.h
as described above).
Architecture- and Chip-Specific Directories.
All processor architecture-specific directories are maintained in sub-directories of
the arch/
directory.
Different chips or SoC's may implement the same processor core.
Chip-specific logic can be found in sub-directories under the architecture
directory.
Current architecture/chip directories are summarized below:
arch/sim
:
A user-mode port of NuttX to the x86 Linux platform is available.
The purpose of this port is primarily to support OS feature development.
This port does not support interrupts or a real timer (and hence no
round robin scheduler) Otherwise, it is complete.
NOTE: This target will not run on Cygwin probably for many reasons but first off because it uses some of the same symbols as does cygwind.dll.
arch/arm
:
This directory holds common ARM architectures.
configs/mcu123-lpc214x
:
The mcu123.com lpc214x development board.
This is a work in progress.
arch/z16f
:
Zilog z16f Microcontroller.
This port uses the Zilog z16f2800100zcog Development Kit.
This port was released with nuttx-0.3.7.
arch/z80
:
This directory holds 8-bit ZiLOG architectures. At present, this includes the
Zilog z80, ez80Acclaim! and z8Encore! Microcontrollers.
arch/z80/include
and arch/z80/src/common
:
Common logic.
arch/z80/include/z80
and arch/z80/src/z80
:
The Z80 port was released in nuttx-0.3.6 has been verified using only a
z80 instruction simulator called z80sim.
This port also uses the SDCC toolchain (http://sdcc.sourceforge.net/)
(verified with version 2.6.0 and 2.7.0).
arch/z80/include/ez80
and arch/z80/src/ez80
:
The ez80Acclaim! port uses the ZiLOG ez80f0910200kitg development kit, eZ80F091 part,
with the Zilog ZDS-II Windows command line tools.
The development environment is Cygwin under WinXP.
This is a work in progress. Verified ez80 support will be announced in a future NuttX release.
arch/z80/include/z8
and arch/z80/src/z8
:
The Z8Encore! port uses either the ZiLOG z8encore000zco development kit, Z8F6403 part,
or the z8f64200100kit development kit, Z8F6423 part with the Zilog ZDS-II Windows command line
tools. The development environment is Cygwin under WinXP.
The initial release, verified only on the ZDS-II ez8 simulator, was released in nuttx-0.3.9.
Deprecated Architecture Directories.
The following architecture directories are deprecated. They have been
replaced by the logic in arm/arm
and will deleted when
arch/arm
is fully verified.
arch/c5471
:
Replaced with arch/arm/include/c5471
and
arch/arm/src/c5471
.
arch/dm320
:
Replaced with arch/arm/include/dm320
and
arch/arm/src/dm320
.
Other ports for the for the TI TMS320DM270 and for MIPS are in various states of progress
The binfmt/
subdirectory contains logic for loading binaries in the file
system into memory in a form that can be used to execute them.
The audio/
subdirectory contains the NuttX audio sub-system.
The configs/
subdirectory contains configuration data for each board.
These board-specific configurations plus the architecture-specific configurations in
the arch/
subdirectory complete define a customized port of NuttX.
The configs directory contains board specific configuration files. Each board must
provide a subdirectory <board-name> under configs/
with the following characteristics:
<board-name> |-- Kconfig |-- include/ | |-- board.h | `-- (board-specific header files) |-- src/ | |-- Makefile | `-- (board-specific source files) |-- <config1-dir> | |-- Make.defs | |-- defconfig | `-- setenv.sh |-- <config2-dir> | |-- Make.defs | |-- defconfig | `-- setenv.sh | ... `-- (other board-specific configuration sub-directories)/
include/
:
This directory contains board specific header files.
This directory will be linked as include/arch/board
at configuration time
and can be included via #include <arch/board/header.h>
.
These header file can only be included by files in arch/
<arch-name>/include/
and arch/
<arch-name>/src/
.
src/
:
This directory contains board specific drivers.
This directory will be linked as <config>/arch/
<arch-name>/src/board
at configuration
time and will be integrated into the build system.
src/Makefile
:
This makefile will be invoked to build the board specific drivers.
It must support the following targets: libext$(LIBEXT)
, clean
, and distclean
.
The configs/
<board-name>/
sub-directory holds all of the
files that are necessary to configure NuttX for the particular board.
A board may have various different configurations using the common source files.
Each board configuration is described by three files: Make.defs
, defconfig
, and setenv.sh
.
Typically, each set of configuration files is retained in a separate configuration sub-directory
(<config1-dir>, <config2-dir>, .. in the above diagram).
The procedure for configuring NuttX is described below,
This paragraph will describe the contents of these configuration files.
Make.defs
: This makefile fragment provides architecture and
tool-specific build options. It will be included by all other
makefiles in the build (once it is installed). This make fragment
should define:
CC
, LD
, AR
, NM
, OBJCOPY
, OBJDUMP
CFLAGS
, LDFLAGS
When this makefile fragment runs, it will be passed TOPDIR
which
is the path to the root directory of the build. This makefile
fragment should include:
$(TOPDIR)/.config
: Nuttx configuration$(TOPDIR)/tools/Config.mk
: Common definitions
Definitions in the Make.defs
file probably depend on some of the
settings in the .config
file. For example, the CFLAGS
will most likely be
different if CONFIG_DEBUG=y
.
The included tools/Config.mk
file contains additional definitions that may
be overridden in the architecture-specific Make.defs file as necessary:
COMPILE
, ASSEMBLE
, ARCHIVE
, CLEAN
, and MKDEP
macros
defconfig
: This is a configuration file similar to the Linux
configuration file. In contains variable/value pairs like:
CONFIG_VARIABLE
=valueThis configuration file will be used at build time:
include/nuttx/config.h
which is included by
most C files in the system.
setenv.sh
: This is a script that can be included that will be installed at
the top level of the directory structure and can be sourced to set any
necessary environment variables.
You will most likely have to customize the default setenv.sh
script in order
for it to work correctly in your environment.
All of the specific boards supported by NuttX are identified in the README.txt file.
Okay, so you have created a new board configuration directory.
Now, how do you hook this board into the configuration system so that you can select with make menuconfig
?
You will need modify the file configs/Kconfig
.
Let's look at the STM32F4-Discovery configuration in the Kconfig
file and see how we would add a new board directory to the configuration.
For this configuration let's say that you new board resides in the directory configs/myboard
;
It uses an MCU selected with CONFIG_ARCH_CHIP_MYMCU
; and you want the board to be selected with CONFIG_ARCH_BOARD_MYBOARD
.
Then here is how you can clone the STM32F4-Discovery configuration in configs/Kconfig
to support your new board configuration.
In configs/Kconfig
for the stm32f4-discovery, you will see a configuration definition like this:
config ARCH_BOARD_STM32F4_DISCOVERY bool "STMicro STM32F4-Discovery board" depends on ARCH_CHIP_STM32F407VG select ARCH_HAVE_LEDS select ARCH_HAVE_BUTTONS select ARCH_HAVE_IRQBUTTONS ---help--- STMicro STM32F4-Discovery board based on the STMicro STM32F407VGT6 MCU.
The above selects the STM32F4-Discovery board.
The select
lines say that the board has both LEDs and buttons and that the board can generate interrupts from the button presses.
You can just copy the above configuration definition to a new location (notice that they the configurations are in alphabetical order).
Then you should edit the configuration to support your board.
The final configuration definition might look something like:
config ARCH_BOARD_MYBOARD bool "My very own board configuration" depends on ARCH_CHIP_MYMCU select ARCH_HAVE_LEDS select ARCH_HAVE_BUTTONS select ARCH_HAVE_IRQBUTTONS ---help--- This options selects the board configuration for my very own board based on the MYMCU processor.
Later in the configs/Kconfig
file, you will see a long, long string configuration with lots of defaults like this:
config ARCH_BOARD string default "amber" if ARCH_BOARD_AMBER default "avr32dev1" if ARCH_BOARD_AVR32DEV1 default "c5471evm" if ARCH_BOARD_C5471EVM ... default "stm32f4discovery" if ARCH_BOARD_STM32F4_DISCOVERY ...
This logic will assign string value to a configuration variable called CONFIG_ARCH_BOARD
that will name the directory where the board-specific files reside.
In our case, these files reside in configs/myboard
and we add the following to the long list of defaults (again in alphabetical order):
default "myboar" if ARCH_BOARD_MYBOARD
Now the build system knows where to find your board configuration!
And finally, add something like this near the bottom of configs/myboard
:
if ARCH_BOARD_MYBOARD source "configs/myboard/Kconfig" endif
This includes additional, board-specific configuration variable definitions in configs/myboard/Kconfig
.
This sub-directory holds the NuttX cryptographic sub-system.
This directory holds architecture-independent device drivers.
drivers/ |-- Kconfig |-- Makefile |-- analog/ | |-- Kconfig | |-- Make.defs | `-- (Common ADC and DAC driver source files) |-- bch/ | |-- Kconfig | |-- Make.defs | `-- (bch driver source files) |-- input/ | |-- Kconfig | |-- Make.defs | `-- (Common touchscreen and keypad driver source files) |-- lcd/ | |-- Kconfig | |-- Make.defs | `-- (Common LCD driver source files) |-- mmcsd/ | |-- Kconfig | |-- Make.defs | `-- (Common MMC/SD card driver source files) |-- mtd/ | |-- Kconfig | |-- Make.defs | `-- (Common memory technology device driver source files) |-- net/ | |-- Kconfig | |-- Make.defs | `-- (Common network driver source files) |-- sensors/ | |-- Kconfig | |-- Make.defs | `-- (Common sensor driver source files) |-- serial/ | |-- Kconfig | |-- Make.defs | `-- (Files for the Calypso SERCOMM driver) |-- serial/ | |-- Kconfig | |-- Make.defs | `-- (Common front-end character drivers for chip-specific UARTs) |-- usbdev/ | |-- Kconfig | |-- Make.defs | `-- (Common USB device driver source files) |-- usbhost/ | |-- Kconfig | |-- Make.defs | `-- (Common USB host driver source files) |-- wireless/ | |-- Kconfig | |-- Make.defs | `-- (Common wireless driver source files) `-- (Various common driver source files)
This directory contains the NuttX file system. This file system is described below.
fs/ |-- Kconfig |-- Makefile |-- fat/ | |-- Kconfig | |-- Make.defs | `-- (FAT file system source files) |-- mmap/ | |-- Kconfig | |-- Make.defs | `-- (RAM-based file mapping source files) |-- nfs/ | |-- Kconfig | |-- Make.defs | `-- (NFS client file system source files) |-- nxffs/ | |-- Kconfig | |-- Make.defs | `-- (NuttX Flash File System (NXFFS) source files) |-- romfs/ | |-- Kconfig | |-- Make.defs | `-- (ROMFS file system source files) `-- (common file system source files)
This directory contains files for graphics/video support under NuttX.
graphics/ |-- Kconfig |-- Makefile |-- nxbe/ | |-- Make.defs | `-- (NuttX graphics back-end (NXBE) source files) |-- nxfont/ | |-- Make.defs | `-- (NuttX graphics font-related (NXFONT) source files) |-- nxglib/ | |-- Make.defs | `-- (NuttX graphics library (NXGL) source files) |-- nxmu/ | |-- Make.defs | `-- (NuttX graphics multi-user (NXMU) server source files) |-- nxsu/ | |-- Make.defs | `-- (NuttX graphics single-user (NXSU) source files) `-- (common file system source files)
This directory holds NuttX header files. Standard header files file retained in can be included in the normal fashion:
include <stdio.h>
include <sys/types.h>
Directory structure:
include/ |-- (standard header files) |-- arpa/ | `-- (Standard header files) |-- cxx/ | `-- (C++ standard header files) |-- netinet/ | `-- (Standard header files) |-- nuttx/ | |-analog/ | | `-- (Analog driver header files) | |-audio/ | | `-- (Audio driver header files) | |-binfmt/ | | `-- (Binary format header files) | |-fs/ | | `-- (File System header files) | |-input/ | | `-- (Input device driver header files) | |-lcd/ | | `-- (LCD driver header files) | |-mtd/ | | `-- (Memory technology device header files) | |-serial/ | | `-- (Serial driver header files) | |-net/ | | `-- (Networking header files) | |-nx/ | | `-- (NX graphics header files) | |-power/ | | `-- (Power management header files) | |-sensors/ | | `-- (Sensor device driver header files) | |-sercomm/ | | `-- (SERCOMM driver header files) | |-serial/ | | `-- (Serial driver header files) | |-spi/ | | `-- (SPI driver header files) | |-syslog/ | | `-- (SYSLOG header files) | |-usb/ | | `-- (USB driver header files) | `-wireless/ | `-- (Wireless device driver header files) `- sys/ `-- (More standard header files)
This is a (almost) empty directory that has a holding place for generated static libraries. The NuttX build system generates a collection of such static libraries in this directory during the compile phaase. These libraries are then in a known place for the final link phase where they are accessed to generated the final binaries.
This directory holds a collection of standard libc-like functions with custom interfaces into NuttX.
Normally the logic in this file builds to a single library (libc.a
).
However, if NuttX is built as a separately compiled kernel (with CONFIG_BUILD_PROTECTED=y
or CONFIG_BUILD_KERNEL=y
), then the contents of this directory are built as two libraries:
One for use by user programs (libuc.a
) and one for use only within the <kernel> space (libkc.a
).
These user/kernel space libraries (along with the sycalls of nuttx/syscall
) are needed to support the two differing protection domains.
Directory structure:
libc/ |-- libgen/ | `-- (Implementation of functions from libgen.h) |-- math/ | `-- (Implementation of functions from fixedmath.h) |-- misc/ | `-- (Implementation of miscellaneous library functions) |-- mqueue/ | `-- (Implementation of some functions from mqueue.h) |-- net/ | `-- (Implementation of network-related library functions) |-- queue/ | `-- (Implementation of functions from queue.h) |-- sched/ | `-- (Implementation of some functions from sched.h) |-- semaphore/ | `-- (Implementation of some functions from semaphore.h) |-- signal/ | `-- (Implementation of some functions from signal.h) |-- stdio/ | `-- (Implementation of functions from stdio.h) |-- stdlib/ | `-- (Implementation of functions from stdlib.h) |-- string/ | `-- (Implementation of functions from string.h) |-- time/ | `-- (Implementation of some functions from time.h) `-- unistd/ `-- (Implementation of some functions from unistd.h)
This directory holds a tiny, minimal standard std C++ that can be used to build some, simple C++ applications in NuttX.
This is the NuttX memory manager.
This directory contains the implementation of the NuttX networking layer including internal socket APIs.
The files forming core of the NuttX RTOS reside here.
If NuttX is built as a separately compiled kernel (with CONFIG_BUILD_PROTECTED=y
or CONFIG_BUILD_KERNEL=y
),
then the contents of this directory are built.
This directory holds a syscall interface that can be used for communication
between user-mode applications and the kernel-mode RTOS.
This directory holds a collection of tools and scripts to simplify configuring, building and maintaining NuttX.
tools/ |-- Makefile.host |-- Makefile.export |-- README.txt |-- configure.sh / configure.bat |-- cfgparser.c |-- cfgparser.h |-- cmpconfig.c |-- cnvwindeps.c |-- copydir.sh / copydir.bat |-- define.sh / define.bat |-- incdir.sh / indir.bat |-- indent.sh |-- link.sh / link.bat |-- mkconfig.c |-- mkexport.sh |-- mkimage.sh |-- mknulldeps.sh |-- mkromfsimg.sh |-- mksyscall.c |-- mkversion.c |-- mkwindeps.sh |-- unlink.sh / unlink.bat |-- version.sh `-- zipme.sh
Refer to the README file in the tools
directory for more information about the individual files.
Some of these tools are discussed below as well in the discussion of configuring and building NuttX.
This directory holds support for hardware-independent wireless support.
The top-level Makefile
in the ${TOPDIR}
directory contains all of the top-level control
logic to build NuttX.
Use of this Makefile
to build NuttX is described below.
3.0 Configuring and Building |
Manual Configuration.
Configuring NuttX requires only copying the
board-specific configuration files into the top level directory which appears in the make files as the make variable, ${TOPDIR}
.
This could be done manually as follows:
configs/
<board-name>/[
<config-dir>/]Make.defs
to ${TOPDIR}/Make.defs
,configs/
<board-name>/[
<config-dir>/]setenv.sh
to ${TOPDIR}/setenv.sh
, andconfigs/
<board-name>/[
<config-dir>/]defconfig
to ${TOPDIR}/.config
Where <board-name> is the name of one of the sub-directories of the
NuttX configs/
directory.
This sub-directory name corresponds to one of the supported boards
identified above.
<config-dir> is the optional, specific configuration directory for the board.
And <app-dir> is the location of the optional application directory.
Automated Configuration. There is a script that automates these steps. The following steps will accomplish the same configuration:
cd tools ./configure.sh <board-name>[/<config-dir>]
There is an alternative Windows batch file, configure.bat
, that can be used instead of configure.sh
in the windows native environment like:
cd tools configure.bat <board-name>[\<config-dir>]
See tools/README.txt
for more information about these scripts.
If your application directory is not in the standard location (../apps
or ../apps-<version>
),
then you should also specify the location of the application directory on the command line like:
cd tools ./configure.sh -a <app-dir> <board-name>[/<config-dir>]
Version Files.
The NuttX build expects to find a version file located in the top-level NuttX build directory.
That version file is called .version
.
The correct version file is installed in each versioned NuttX released.
However, if you are working from an GIT snapshot, then there will be no version file.
If there is no version file, the top-level Makefile
will create a dummy .version
file on the first make.
This dummy version file will contain all zeroes for version information.
If that is not what you want, they you should run the version.sh
script to create a better .version
file.
You can get help information from the version.sh
script using the -h
option.
For example:
$ tools/version.sh -h tools/version.sh is a tool for generation of proper version files for the NuttX build USAGE: tools/version.sh [-d|-h] [-b build] -v <major.minor> <outfile-path> Where: -d Enable script debug -h show this help message and exit -v <major.minor> The NuttX version number expressed a major and minor number separated by a period <outfile-path> The full path to the version file to be created
As an example, the following command will generate a version file for version 6.1 using the current GIT revision number:
tools/version.h -v 6.1 .version
The .version
file is also used during the build process to create a C header file at include/nuttx/version.h
that contains the same version information.
That version file may be used by your C applications for, as an example, reporting version information.
Additional Configuration Steps.
The remainder of configuration steps will be performed by ${TOPDIR}/Makefile
the first time the system is built as described below.
Building NuttX. Once NuttX has been configured as described above, it may be built as follows:
cd ${TOPDIR} source ./setenv.sh make
The ${TOPDIR}
directory holds:
Makefile
that controls the NuttX build.
That directory also holds:
.config
that describes the current configuration.Make.defs
that provides customized build targets, andsetenv.sh
that sets up the configuration environment for the build.
The setenv.sh
contains Linux/Cygwin environmental settings that are needed for the build.
The specific environmental definitions are unique for each board but should include, as a minimum, updates to the PATH
variable to include the full path to the architecture-specific toolchain identified in Make.defs
.
The setenv.sh
only needs to be source'ed at the beginning of a session.
The system can be re-made subsequently by just typing make
.
First Time Make. Additional configuration actions will be taken the first time that system is built. These additional steps include:
include/nuttx/config.h
using the ${TOPDIR}/.config
file.${TOPDIR}/.version
with version 0.0 if one does not exist.include/nuttx/version.h
using the ${TOPDIR}/.version
file.${TOPDIR}/arch/
<arch-name>/include
at ${TOPDIR}/include/arch
.${TOPDIR}/configs/
<board-name>/include
at ${TOPDIR}/include/arch/board
.${TOPDIR}/configs/
<board-name>/src
at ${TOPDIR}/arch/
<arch-name>/src/board
${APPDIR}/include
at ${TOPDIR}/include/apps
4.0 Architecture APIs |
The file include/nuttx/arch.h
identifies by prototype all of the APIs that must
be provided by the architecture specific logic.
The internal OS APIs that architecture-specific logic must
interface with also also identified in include/nuttx/arch.h
or in
other header files.
Common Microprocessor Interfaces.
Any interface that is common to all microprocessors should be prefixed with up_
and prototyped in include/nuttx/arch.h
.
The definitions in that header file provide the common interface between NuttX and the architecture-specific implementation in arch/
.
up_
is supposed to stand for microprocessor; theu
is like the Greek letter micron: µ. So it would beµP
which is a common shortening of the word microprocessor. I don't like that name very much. I wish I would have used a more obvious prefix likearch_
instead -- then I would not have to answer this question so often.
Microprocessor-Specific Interfaces.
An interface which is unique to a certain microprocessor should be prefixed with the name of the microprocessor, for example stm32_
, and be prototyped in some header file in the arch/
directories.
There is also a arch/<architecture>/include/<chip>/chip.h
header file that can be used to communicate other microprocessor-specific information between the board logic and even application logic.
Application logic may, for example, need to know specific capabilities of the chip.
Prototypes in that chip.h
header file should follow the microprocessor-specific naming convention.
Common Board Interfaces.
Any interface that is common to all boards should be prefixed with board_
and should also be prototyped in include/nuttx/arch.h
.
These board_
definitions provide the interface between the board-level logic and the architecture-specific logic.
There is also a configs/<board>/include/board.h
header file that can be used to communicate other board-specific information between the architecture logic and even application logic.
Any definitions which are common between a single architecture and several boards should go in this board.h
header file;
include/nuttx/arch.h
is reserved for board-related definitions common to all architectures.
Board-Specific Interfaces.
Any interface which is unique to a board should be prefixed with the board name, for example stm32f4discovery_
.
Sometimes the board name is too long so stm32_
would be okay too.
These should be prototyped in configs/<board>/src/<board>.h
and should not be used outside of that directory since board-specific definitions have no meaning outside of the board directory.
up_initialize()
Function Prototype: void up_initialize(void);
Description.
up_initialize()
will be called once during OS
initialization after the basic OS services have been
initialized. The architecture specific details of
initializing the OS will be handled here. Such things as
setting up interrupt service routines, starting the
clock, and registering device drivers are some of the
things that are different for each processor and hardware
platform.
up_initialize()
is called after the OS initialized but
before the init process has been started and before the
libraries have been initialized. OS services and driver
services are available.
up_idle()
Function Prototype: void up_idle(void);
Description.
up_idle()
is the logic that will be executed
when their is no other ready-to-run task. This is processor
idle time and will continue until some interrupt occurs to
cause a context switch from the idle task.
Processing in this state may be processor-specific. e.g., this is where power management operations might be performed.
up_initial_state()
Function Prototype: void up_initial_state(FAR struct tcb_s *tcb);
Description. A new thread is being started and a new TCB has been created. This function is called to initialize the processor specific portions of the new TCB.
This function must setup the initial architecture registers and/or stack so that execution will begin at tcb->start on the next context switch.
This function may also need to set up processor registers so that the new thread executes
with the correct privileges.
If CONFIG_BUILD_PROTECTED
or CONFIG_BUILD_KERNEL
have been selected in the NuttX configuration, then special initialization may need to be performed depending on the task type specified in the TCB's flags field:
Kernel threads will require kernel-mode privileges;
User tasks and pthreads should have only user-mode privileges.
If neither CONFIG_BUILD_PROTECTED
nor CONFIG_BUILD_KERNEL
have been selected, then all threads should have kernel-mode privileges.
up_create_stack()
Function Prototype: STATUS up_create_stack(FAR struct tcb_s *tcb, size_t stack_size, uint8_t ttype);
Description. Allocate a stack for a new thread and setup up stack-related information in the TCB.
The following TCB fields must be initialized:
adj_stack_size
: Stack size after adjustment for hardware,
processor, etc. This value is retained only for debug
purposes.stack_alloc_ptr
: Pointer to allocated stackadj_stack_ptr
: Adjusted stack_alloc_ptr
for HW. The
initial value of the stack pointer.
Input Parameters:
tcb
: The TCB of new task.
stack_size
: The requested stack size. At least this much must be allocated.
ttype
: The thread type.
This may be one of following (defined in include/nuttx/sched.h
):
TCB_FLAG_TTYPE_TASK
: Normal user taskTCB_FLAG_TTYPE_PTHREAD
: User pthreadTCB_FLAG_TTYPE_KERNEL
: Kernel threadThis thread type is normally available in the flags field of the TCB, however, there are certain contexts where the TCB may not be fully initialized when up_create_stack is called.
If CONFIG_BUILD_PROTECTED
or CONFIG_BUILD_KERNEL
are defined, then this thread type may affect how the stack is allocated. For example, kernel thread stacks should be allocated from protected kernel memory. Stacks for user tasks and threads must come from memory that is accessible to user code.
up_use_stack()
Function Prototype:
STATUS up_use_stack(FAR struct tcb_s *tcb, FAR void *stack, size_t stack_size);
Description.
Setup up stack-related information in the TCB using pre-allocated stack memory.
This function is called only from task_init()
when a task or kernel thread is started (never for pthreads).
The following TCB fields must be initialized:
adj_stack_size
: Stack size after adjustment for hardware,
processor, etc. This value is retained only for debug
purposes.stack_alloc_ptr
: Pointer to allocated stackadj_stack_ptr
: Adjusted stack_alloc_ptr
for HW. The
initial value of the stack pointer.
Input Parameters:
tcb
: The TCB of new task.
stack_size
: The allocated stack size.
NOTE: Unlike up_stack_create()
and up_stack_release
, this function does not require the task type (ttype
) parameter.
The TCB flags will always be set to provide the task type to up_use_stack()
if the information needs that information.
up_stack_frame()
Function Prototype: FAR void *up_stack_frame(FAR struct tcb_s *tcb, size_t frame_size);
Description.
Allocate a stack frame in the TCB's stack to hold thread-specific data.
This function may be called any time after up_create_stack()
or up_use_stack()
have been called but before the task has been started.
Thread data may be kept in the stack (instead of in the TCB) if it is accessed by the user code directly.
This includes such things as argv[]
.
The stack memory is guaranteed to be in the same protection domain as the thread.
The following TCB fields will be re-initialized:
adj_stack_size
: Stack size after removal of the stack frame from the stack.
adj_stack_ptr
: Adjusted initial stack pointer after the frame has been removed from the stack.
This will still be the initial value of the stack pointer when the task is started.
Input Parameters:
tcb
:
The TCB of new task.
frame_size
:
The size of the stack frame to allocate.
Returned Value: A pointer to bottom of the allocated stack frame. NULL will be returned on any failures. The alignment of the returned value is the same as the alignment of the stack itself
up_release_stack()
Function Prototype: void up_release_stack(FAR struct tcb_s *dtcb);
Description. A task has been stopped. Free all stack related resources retained int the defunct TCB.
Input Parameters:
dtcb
:
The TCB containing information about the stack to be released.
ttype
: The thread type.
This may be one of following (defined in include/nuttx/sched.h
):
TCB_FLAG_TTYPE_TASK
: Normal user taskTCB_FLAG_TTYPE_PTHREAD
: User pthreadTCB_FLAG_TTYPE_KERNEL
: Kernel threadThis thread type is normally available in the flags field of the TCB, however, there are certain error recovery contexts where the TCB may not be fully initialized when up_release_stack is called.
If CONFIG_BUILD_PROTECTED
or CONFIG_BUILD_KERNEL
are defined, then this thread type may affect how the stack is freed.
For example, kernel thread stacks may have been allocated from protected kernel memory.
Stacks for user tasks and threads must have come from memory that is accessible to user
up_unblock_task()
Function Prototype: void up_unblock_task(FAR struct tcb_s *tcb);
Description. A task is currently in an inactive task list but has been prepped to execute. Move the TCB to the ready-to-run list, restore its context, and start execution.
This function is called only from the NuttX scheduling logic. Interrupts will always be disabled when this function is called.
Input Parameters:
tcb
: Refers to the tcb to be unblocked. This tcb is
in one of the waiting tasks lists. It must be moved to
the ready-to-run list and, if it is the highest priority
ready to run tasks, executed.
up_block_task()
Function Prototype: void up_block_task(FAR struct tcb_s *tcb, tstate_t task_state);
Description. The currently executing task at the head of the ready to run list must be stopped. Save its context and move it to the inactive list specified by task_state. This function is called only from the NuttX scheduling logic. Interrupts will always be disabled when this function is called.
Input Parameters:
tcb
: Refers to a task in the ready-to-run list (normally
the task at the head of the list). It most be
stopped, its context saved and moved into one of the
waiting task lists. It it was the task at the head
of the ready-to-run list, then a context to the new
ready to run task must be performed.
task_state
: Specifies which waiting task list should be
hold the blocked task TCB.
up_release_pending()
Function Prototype: void up_release_pending(void);
Description. When tasks become ready-to-run but cannot run because pre-emption is disabled, they are placed into a pending task list. This function releases and makes ready-to-run all of the tasks that have collected in the pending task list. This can cause a context switch if a new task is placed at the head of the ready to run list.
This function is called only from the NuttX scheduling logic when pre-emption is re-enabled. Interrupts will always be disabled when this function is called.
up_reprioritize_rtr()
Function Prototype: void up_reprioritize_rtr(FAR struct tcb_s *tcb, uint8_t priority);
Description. Called when the priority of a running or ready-to-run task changes and the reprioritization will cause a context switch. Two cases:
This function is called only from the NuttX scheduling logic. Interrupts will always be disabled when this function is called.
Input Parameters:
tcb
: The TCB of the task that has been reprioritized
priority
: The new task priority
_exit()
Function Prototype: void _exit(int status) noreturn_function;
Description. This function causes the currently executing task to cease to exist. This is a special case of task_delete().
Unlike other UP APIs, this function may be called directly from user programs in various states. The implementation of this function should disable interrupts before performing scheduling operations.
up_assert()
Function Prototype:
void up_assert(FAR const uint8_t *filename, int linenum);
Description. Assertions may be handled in an architecture-specific way.
up_schedule_sigaction()
Function Prototype:
void up_schedule_sigaction(FAR struct tcb_s *tcb, sig_deliver_t sigdeliver);
Description. This function is called by the OS when one or more signal handling actions have been queued for execution. The architecture specific code must configure things so that the 'sigdeliver' callback is executed on the thread specified by 'tcb' as soon as possible.
This function may be called from interrupt handling logic.
This operation should not cause the task to be unblocked nor should it cause any immediate execution of sigdeliver. Typically, a few cases need to be considered:
This API is NOT required if CONFIG_DISABLE_SIGNALS
is defined.
up_allocate_heap()
Function Prototype: void up_allocate_heap(FAR void **heap_start, size_t *heap_size);
Description. This function will be called to dynamically set aside the heap region.
For the kernel build (CONFIG_BUILD_PROTECTED=y
or CONFIG_BUILD_KERNEL=y
) with both kernel- and user-space heaps (CONFIG_MM_KERNEL_HEAP=y
), this function provides the size of the unprotected, user-space heap.
If a protected kernel-space heap is provided, the kernel heap must be allocated (and protected) by an analogous up_allocate_kheap()
.
up_interrupt_context()
Function Prototype: bool up_interrupt_context(void)
Description. Return true if we are currently executing in the interrupt handler context.
up_disable_irq()
Function Prototype:
#ifndef CONFIG_ARCH_NOINTC void up_disable_irq(int irq); #endif
Description. Disable the IRQ specified by 'irq' On many architectures, there are three levels of interrupt enabling: (1) at the global level, (2) at the level of the interrupt controller, and (3) at the device level. In order to receive interrupts, they must be enabled at all three levels.
This function implements enabling of the device specified by 'irq' at the interrupt controller level if supported by the architecture (up_irq_save() supports the global level, the device level is hardware specific).
If the architecture does not support up_disable_irq
,
CONFIG_ARCH_NOINTC
should be defined in the NuttX configuration file.
Since this API cannot be supported on all architectures, it should be
avoided in common implementations where possible.
up_enable_irq()
Function Prototype:
#ifndef CONFIG_ARCH_NOINTC void up_enable_irq(int irq); #endif
Description. This function implements disabling of the device specified by 'irq' at the interrupt controller level if supported by the architecture (up_irq_restore() supports the global level, the device level is hardware specific).
If the architecture does not support up_disable_irq
,
CONFIG_ARCH_NOINTC
should be defined in the NuttX configuration file.
Since this API cannot be supported on all architectures, it should be
avoided in common implementations where possible.
up_prioritize_irq()
Function Prototype:
#ifdef CONFIG_ARCH_IRQPRIO void up_enable_irq(int irq); #endif
Description. Set the priority of an IRQ.
If the architecture supports up_enable_irq
,
CONFIG_ARCH_IRQPRIO
should be defined in the NuttX configuration file.
Since this API cannot be supported on all architectures, it should be
avoided in common implementations where possible.
up_putc()
Function Prototype: int up_putc(int ch);
Description. This is a debug interface exported by the architecture-specific logic. Output one character on the console
System Timer
In most implementations, system time is provided by a timer interrupt.
That timer interrupt runs at rate determined by CONFIG_USEC_PER_TICK
(default 10000 microseconds or 100Hz. If CONFIG_SCHED_TICKLESS
is selected, the default is 100 microseconds).
The timer generates an interrupt each CONFIG_USEC_PER_TICK
microseconds and increments a counter called g_system_timer
.
g_system_timer
then provides a time-base for calculating up-time and elapsed time intervals in units of CONFIG_USEC_PER_TICK
.
The range of g_system_timer
is, by default, 32-bits.
However, if the MCU supports type long long
and CONFIG_SYSTEM_TIME16
is selected,
a 64-bit system timer will be supported instead.
System Timer Accuracy
On many system, the exact timer interval specified by CONFIG_USEC_PER_TICK
cannot be achieved due to limitations in frequencies or in dividers.
As a result, the time interval specified by CONFIG_USEC_PER_TICK
may only be approximate and there may be small errors in the apparent up-time time.
These small errors, however, will accumulate over time and after a long period of time may have an unacceptably large error in the apparent up-time of the MCU.
CONFIG_USEC_PER_TICK
and if there you require accurate up-time for the MCU, then there are measures that you can take:
CONFIG_USEC_PER_TICK
to a different value so that an exactly CONFIG_USEC_PER_TICK
can be realized.
Delta-Sigma Modulation Example.
Consider this case: The system timer is a count-up timer driven at 32.768KHz.
There are dividers that can be used, but a divider of one yields the highest accuracy.
This counter counts up until the count equals a match value, then a timer interrupt is generated.
The desire frequency is 100Hz (CONFIG_USEC_PER_TICK
is 10000).
This exact frequency of 100Hz cannot be obtained in this case. In order to obtain that exact frequency a match value of 327.68 would have to be provided. The closest integer value is 328 but the ideal match value is between 327 and 328. The closest value, 328, would yield an actual timer frequency of 99.9Hz! That will may cause significant timing errors in certain usages.
Use of Delta-Sigma Modulation can eliminate this error in the long run. Consider this example implementation:
accumulator = 0; match = 328;
if (match == 328) { accumulator += 32; // 100*(328 - 327.68) } else { accumulator -= 68; // (100*(327 - 327.68) }
if (accumulator < 0) { match = 328; } else { match = 327; }
In this way, the timer interval is controlled from interrupt-to-interrupt to produce an average frequency of exactly 100Hz.
To enable hardware module use the following configuration options:
CONFIG_RTC
CONFIG_RTC_EXTERNAL
CONFIG_RTC_EXTERNAL
will configure the operating
system so that it defers initialization of its time facilities.
CONFIG_RTC_DATETIME
CONFIG_RTC_DATETIME
is selected, it specifies this second kind of RTC.
In this case, the RTC is used to "seed"" the normal NuttX timer and the NuttX system timer
provides for higher resolution time.
CONFIG_RTC_HIRES
CONFIG_RTC_DATETIME
not selected, then the simple, battery backed counter is used.
There are two different implementations of such simple counters based on the time resolution of the counter:
The typical RTC keeps time to resolution of 1 second, usually supporting a 32-bit time_t
value.
In this case, the RTC is used to "seed" the normal NuttX timer and the NuttX timer provides for higher resolution time.
If CONFIG_RTC_HIRES
is enabled in the NuttX configuration, then the RTC provides higher resolution time and completely replaces the system timer for purpose of date and time.
CONFIG_RTC_FREQUENCY
CONFIG_RTC_HIRES
is defined, then the frequency of the high resolution RTC must be provided.
If CONFIG_RTC_HIRES
is not defined, CONFIG_RTC_FREQUENCY
is assumed to be one.
CONFIG_RTC_ALARM
which requires the following base functions to read and set time:
up_rtc_initialize()
.
Initialize the builtin, MCU hardware RTC per the selected configuration.
This function is called once very early in the OS initialization sequence.
NOTE that initialization of external RTC hardware that depends on the
availability of OS resources (such as SPI or I2C) must be deferred
until the system has fully booted. Other, RTC-specific initialization
functions are used in that case.
up_rtc_time()
.
Get the current time in seconds. This is similar to the standard time()
function.
This interface is only required if the low-resolution RTC/counter hardware implementation selected.
It is only used by the RTOS during initialization to set up the system time when CONFIG_RTC
is set
but neither CONFIG_RTC_HIRES
nor CONFIG_RTC_DATETIME
are set.
up_rtc_gettime()
.
Get the current time from the high resolution RTC clock/counter.
This interface is only supported by the high-resolution RTC/counter hardware implementation.
It is used to replace the system timer (g_system_tick
).
up_rtc_settime()
.
Set the RTC to the provided time.
All RTC implementations must be able to set their time based on a standard timespec.
The system tick is represented by::
g_system_timer
Running at rate of system base timer, used for time-slicing, and so forth.
If hardware RTC is present (CONFIG_RTC
) and and high-resolution timing
is enabled (CONFIG_RTC_HIRES
), then after successful
initialization variables are overridden by calls to up_rtc_gettime()
which is
running continuously even in power-down modes.
In the case of CONFIG_RTC_HIRES
is set the g_system_timer
keeps counting at rate of a system timer, which however, is disabled in power-down mode.
By comparing this time and RTC (actual time) one may determine the actual system active time.
To retrieve that variable use:
Default System Timer.
By default, a NuttX configuration uses a periodic timer interrupt that drives all system timing. The timer is provided by architecture-specific code that calls into NuttX at a rate controlled by CONFIG_USEC_PER_TICK
. The default value of CONFIG_USEC_PER_TICK
is 10000 microseconds which corresponds to a timer interrupt rate of 100 Hz.
On each timer interrupt, NuttX does these things:
CONFIG_USEC_PER_TICK
microseconds.
What is wrong with this default system timer? Nothing really. It is reliable and uses only a small fraction of the CPU band width. But we can do better. Some limitations of default system timer are, in increasing order of importance:
CONFIG_USEC_PER_TICK
. So nothing that be time with resolution finer than 10 milliseconds be default. To increase this resolution, CONFIG_USEC_PER_TICK
an be reduced. However, then the system timer interrupts use more of the CPU bandwidth processing useless interrupts.
wfi
or wfe
instructions for example). But each interrupt awakens the system from this low power mode. Therefore, higher rates of interrupts cause greater power consumption.
Tickless OS. The so-called Tickless OS provides one solution to issue. The basic concept here is that the periodic, timer interrupt is eliminated and replaced with a one-shot, interval timer. It becomes event driven instead of polled: The default system timer is a polled design. On each interrupt, the NuttX logic checks if it needs to do anything and, if so, it does it.
Using an interval timer, one can anticipate when the next interesting OS event will occur, program the interval time and wait for it to fire. When the interval time fires, then the scheduled activity is performed.
nuttx/arch/sim/src/up_tickless.c
. There is another example for the Atmel SAMA5 at nuttx/arch/arm/src/sama5/sam_tickless.c
. These paragraphs will explain how to provide the Tickless OS support to any platform.
CONFIG_ARCH_HAVE_TICKLESS
:
If the platform provides support for the Tickless OS, then this setting should be selected in the Kconfig
file for the board. Here is what the selection looks in the arch/Kconfig
file for the simulated platform:
config ARCH_SIM bool "Simulation" select ARCH_HAVE_TICKLESS ---help--- Linux/Cywgin user-mode simulation.
When the simulation platform is selected, ARCH_HAVE_TICKLESS
is automatically selected, informing the configuration system that Tickless OS options can be selected.
CONFIG_SCHED_TICKLESS
:
If CONFIG_ARCH_HAVE_TICKLESS
is selected, then it will enable the Tickless OS features in NuttX.
CONFIG_SCHED_TICKLESS_ALARM
:
The tickless option can be supported either via a simple interval timer (plus elapsed time) or via an alarm. The interval timer allows programming events to occur after an interval. With the alarm, you can set a time in the future and get an event when that alarm goes off. This option selects the use of an alarm.
The advantage of an alarm is that it avoids some small timing errors; the advantage of the use of the interval timer is that the hardware requirement may be less.
CONFIG_USEC_PER_TICK
:
This option is not unique to Tickless OS operation, but changes its relevance when the Tickless OS is selected.
In the default configuration where system time is provided by a periodic timer interrupt, the default system timer is configure the timer for 100Hz or CONFIG_USEC_PER_TICK=10000
. If CONFIG_SCHED_TICKLESS
is selected, then there are no system timer interrupt. In this case, CONFIG_USEC_PER_TICK
does not control any timer rates. Rather, it only determines the resolution of time reported by clock_systimer()
and the resolution of times that can be set for certain delays including watchdog timers and delayed work.
In this case there is still a trade-off: It is better to have the CONFIG_USEC_PER_TICK
as low as possible for higher timing resolution. However, the the time is currently held in unsigned int
. On some systems, this may be 16-bits in width but on most contemporary systems it will be 32-bits. In either case, smaller values of CONFIG_USEC_PER_TICK
will reduce the range of values that delays that can be represented. So the trade-off is between range and resolution (you could also modify the code to use a 64-bit value if you really want both).
The default, 100 microseconds, will provide for a range of delays up to 120 hours.
This value should never be less than the underlying resolution of the timer. Errors may ensue.
The interfaces that must be provided by the platform specified code are defined in include/nuttx/arch.h
, listed below, and summarized in the following paragraphs:
up_timer_initialize()
:
Initializes the timer facilities. Called early in the intialization sequence (by up_intialize()
).
up_timer_gettime()
:
Returns the current time from the platform specific time source.
The tickless option can be supported either via a simple interval timer (plus elapsed time) or via an alarm. The interval timer allows programming events to occur after an interval. With the alarm, you can set a time in* the future and get an event when that alarm goes off.
If CONFIG_SCHED_TICKLESS_ALARM
is defined, then the platform code must provide the following:
up_alarm_cancel()
:
Cancels the alarm.
up_alarm_start()
:
Enables (or re-enables) the alaram.
If CONFIG_SCHED_TICKLESS_ALARM
is notdefined, then the platform code must provide the following verify similar functions:
up_timer_cancel()
:
Cancels the interval timer.
up_timer_start()
:
Starts (or re-starts) the interval timer.
Note that a platform-specific implementation would probably require two hardware timers: (1) A interval timer to satisfy the requirements of up_timer_start()
and up_timer_cancel()
, and a (2) a counter to handle the requirement of up_timer_gettime()
. Ideally, both timers would run at the rate determined by CONFIG_USEC_PER_TICK
(and certainly never slower than that rate).
Since timers are a limited resource, the use of two timers could be an issue on some systems.
The job could be done with a single timer if, for example, the single timer were kept in a free-running at all times. Some timer/counters have the capability to generate a compare interrupt when the timer matches a comparison value but also to continue counting without stopping. If your hardware supports such counters, one might used the CONFIG_SCHED_TICKLESS_ALARM
option and be able to simply set the comparison count at the value of the free running timer PLUS the desired delay. Then you could have both with a single timer: An alarm and a free-running counter with the same timer!
In addition to these imported interfaces, the RTOS will export the following interfaces for use by the platform-specific interval timer implementation:
sched_alarm_expiration()
. Called by the platform-specific logic when the alarm expires.
sched_timer_expiration()
. Called by the platform-specific logic when the interval time expires.
up_timer_initialize()
Function Prototype:
#include <nuttx/arch.h> void up_timer_initialize(void);
Description:
up_intialize()
. On return, the current up-time should be available from up_timer_gettime()
and the interval timer is ready for use (but not actively timing).
Input Parameters:
Returned Value:
OK
) on success; a negated errno
value on failure.
Assumptions:
up_timer_gettime()
Function Prototype:
#include <nuttx/arch.h> int up_timer_gettime(FAR struct timespec *ts);
Description:
Return the elapsed time since power-up (or, more correctly, sinceup_timer_initialize()
was called). This function is functionally equivalent to clock_gettime()
for the clock ID CLOCK_MONOTONIC
. This function provides the basis for reporting the current time and also is used to eliminate error build-up from small errors in interval time calculations.
Input Parameters:
ts
: Provides the location in which to return the up-time..
Returned Value:
OK
) on success; a negated errno
value on failure.
Assumptions:
up_alarm_cancel()
Function Prototype:
#include <nuttx/arch.h> int up_alarm_cancel(FAR struct timespec *ts);
Description:
Cancel the alarm and return the time of cancellation of the alarm. These two steps need to be as nearly atomic as possible.sched_timer_expiration()
will not be called unless the alarm is restarted with up_alarm_start()
. If, as a race condition, the alarm has already expired when this function is called, then time returned is the current time.
Input Parameters:
ts
: Location to return the expiration time. The current time should be returned if the timer is not active. ts
may be NULL
in which case the time is not returnedReturned Value:
OK
) on success; a negated errno
value on failure.
Assumptions:
up_alarm_start()
Function Prototype:
#include <nuttx/arch.h> int up_alarm_start(FAR const struct timespec *ts);
Description:
Start the alarm.sched_timer_expiration()
will be called when the alarm occurs (unless up_alaram_cancel
is called to stop it).
Input Parameters:
ts
: The time in the future at the alarm is expected to occur. When the alarm occurs the timer logic will call sched_timer_expiration()
.Returned Value:
OK
) on success; a negated errno
value on failure.
Assumptions:
up_timer_cancel()
Function Prototype:
#include <nuttx/arch.h> int up_timer_cancel(FAR struct timespec *ts);
Description:
Cancel the interval timer and return the time remaining on the timer. These two steps need to be as nearly atomic as possible.sched_timer_expiration()
will not be called unless the timer is restarted with up_timer_start()
. If, as a race condition, the timer has already expired when this function is called, then that pending interrupt must be cleared so that sched_timer_expiration()
is not called spuriously and the remaining time of zero should be returned.
Input Parameters:
ts
: Location to return the remaining time. Zero should be returned if the timer is not active.Returned Value:
OK
) on success; a negated errno
value on failure.
Assumptions:
up_timer_start()
Function Prototype:
#include <nuttx/arch.h> int up_timer_start(FAR const struct timespec *ts);
Description:
Start the interval timer.sched_timer_expiration()
will be called at the completion of the timeout (unless up_timer_cancel()
is called to stop the timing).
Input Parameters:
ts
: Provides the time interval until sched_timer_expiration()
is called.Returned Value:
OK
) on success; a negated errno
value on failure.
Assumptions:
NuttX provides a general watchdog timer facility.
This facility allows the NuttX user to specify a watchdog timer function
that will run after a specified delay.
The watchdog timer function will run in the context of the timer interrupt handler.
Because of this, a limited number of NuttX interfaces are available to he watchdog timer function.
However, the watchdog timer function may use mq_send()
, sigqueue()
,
or kill()
to communicate with NuttX tasks.
Function Prototype:
#include <nuttx/wdog.h> WDOG_ID wd_create(void); void wd_static(FAR struct wdog_s *wdog);
Description: The wd_create()
function will create a timer by allocating the appropriate resources for the watchdog. The wd_create()
function returns a pointer to a fully initialized, dynamically allocated struct wdog_s
instance (which is typedef
'ed as WDOG_ID
);
wd_static()
performs the equivalent initialization of a statically allocated struct wdog_s
instance. No allocation is performed in this case. The initializer definition, WDOG_INITIALIZER
is also available for initialization of static instances of struct wdog_s
. NOTE: wd_static()
is also implemented as a macro definition.
Input Parameters: None.
Returned Value:
Assumptions/Limitations:
POSIX Compatibility: This is a NON-POSIX interface. VxWorks provides the following comparable interface:
WDOG_ID wdCreate (void);
Differences from the VxWorks interface include:
Function Prototype:
#include <nuttx/wdog.h> int wd_delete(WDOG_ID wdog);
Description: The wd_delete function will deallocate a watchdog timer previously allocated via wd_create()
. The watchdog timer will be removed from the timer queue if has been started.
This function need not be called for statically allocated timers (but it is not harmful to do so).
Input Parameters:wdog
. The watchdog ID to delete. This is actually a
pointer to a watchdog structure.
Returned Value:
Assumptions/Limitations: It is the responsibility of the caller to assure that the watchdog is inactive before deleting it.
POSIX Compatibility: This is a NON-POSIX interface. VxWorks provides the following comparable interface:
STATUS wdDelete (WDOG_ID wdog);
Differences from the VxWorks interface include:
Function Prototype:
#include <nuttx/wdog.h> int wd_start(WDOG_ID wdog, int delay, wdentry_t wdentry, int argc, ....);
Description: This function adds a watchdog to the timer queue. The specified watchdog function will be called from the interrupt level after the specified number of ticks has elapsed. Watchdog timers may be started from the interrupt level.
Watchdog times execute in the context of the timer interrupt handler.
Watchdog timers execute only once.
To replace either the timeout delay or the function to be executed, call wd_start again with the same wdog; only the most recent wd_start() on a given watchdog ID has any effect.
Input Parameters:
wdog
. Watchdog ID
delay
. Delay count in clock ticks
wdentry
. Function to call on timeout
argc
. The number of uint32_t parameters to pass to wdentry.
...
. uint32_t size parameters to pass to wdentry
Returned Value:
Assumptions/Limitations: The watchdog routine runs in the context of the timer interrupt handler and is subject to all ISR restrictions.
POSIX Compatibility: This is a NON-POSIX interface. VxWorks provides the following comparable interface:
STATUS wdStart (WDOG_ID wdog, int delay, FUNCPTR wdentry, int parameter);
Differences from the VxWorks interface include:
Function Prototype:
#include <nuttx/wdog.h> int wd_cancel(WDOG_ID wdog);
Description: This function cancels a currently running watchdog timer. Watchdog timers may be canceled from the interrupt level.
Input Parameters:
wdog
. ID of the watchdog to cancel.
Returned Value:
Assumptions/Limitations:
POSIX Compatibility: This is a NON-POSIX interface. VxWorks provides the following comparable interface:
STATUS wdCancel (WDOG_ID wdog);
Function Prototype:
#include <nuttx/wdog.h> Sint wd_gettime(WDOG_ID wdog);
Description: This function returns the time remaining before the specified watchdog expires.
Input Parameters:
wdog
. Identifies the watchdog that the request is for.Returned Value: The time in system ticks remaining until the watchdog time expires. Zero means either that wdog is not valid or that the wdog has already expired.
When a watchdog expires, the callback function with this type is called:
typedef void (*wdentry_t)(int argc, ...);
Where argc
is the number of wdparm_t
type arguments that follow.
The arguments are passed as scalar wdparm_t
values. For systems where the sizeof(pointer) < sizeof(uint32_t)
, the following union defines the alignment of the pointer within the uint32_t
. For example, the SDCC MCS51 general pointer is 24-bits, but uint32_t
is 32-bits (of course).
sizeof(pointer) <= sizeof(uintptr_t)
by definition.
union wdparm_u { FAR void *pvarg; /* The size one generic point */ uint32_t dwarg; /* Big enough for a 32-bit value in any case */ uintptr_t uiarg; /* sizeof(uintptr_t) >= sizeof(pointer) */ }; #if UINTPTR_MAX >= UINT32_MAX typedef uintptr_t wdparm_t; #else typedef uint32_t wdparm_t; #endif
Work Queues. NuttX provides work queues. Work queues are threads that service a queue of work items to be performed. They are useful for off-loading work to a different threading context, for delayed processing, or for serializing activities.
Classes of Work Queues. There are three different classes of work queues, each with different properties and intended usage. These class of work queues along with the the common work queue interface are described in the following paragraphs.
High Priority Kernel Work queue. The dedicated high-priority work queue is intended to handle delayed processing from interrupt handlers. This work queue is required for some drivers but, if there are no complaints, can be safely disabled. The high priority worker thread also performs garbage collection -- completing any delayed memory deallocations from interrupt handlers. If the high-priority worker thread is disabled, then that clean up will be performed either by (1) the low-priority worker thread, if enabled, and if not (2) the IDLE thread instead (which runs at the lowest of priority and may not be appropriate if memory reclamation is of high priority)
Device Driver Bottom Half. The higher priority worker thread is intended to serve as the bottom half for device drivers. As a consequence it must run at a very high, fixed priority rivalling the priority of the interrupt handler itself. Typically, the high priority work queue should be the highest priority thread in your system (the default priority is 224).
Compared to the Low Priority Kernel Work Queue. For less critical, lower priority, application oriented worker thread support, consider enabling the lower priority work queue. The lower priority work queue runs at a lower priority, of course, but has the added advantage that it supports priority inheritance (if <config> CONFIG_PRIORITY_INHERITANCE is also selected): The priority of the lower priority worker thread can then be adjusted to match the highest priority client.
Configuration Options.
CONFIG_SCHED_HPWORK
.
Enables the hight prioirity work queue.
CONFIG_SCHED_HPWORKPRIORITY
.
The execution priority of the high-priority worker thread. Default: 224
CONFIG_SCHED_HPWORKPERIOD
.
How often the worker thread re-checks for work in units of microseconds. This work period is really only necessary if the the high priority thread is performing periodic garbage collection. The worker thread will be awakened immediately with it is queued work to be done. If the high priority worker thread is performing garbage collection, then the default is 50*1000 (50 MS). Otherwise, if the lower priority worker thread is performing garbage collection, the default is 100*1000.
CONFIG_SCHED_HPWORKSTACKSIZE
.
The stack size allocated for the worker thread in bytes. Default: 2048.
Common Configuration Options. These options apply to all work queues:
CONFIG_SIG_SIGWORK
The signal number that will be used to wake-up the worker thread. This same signal is used with the Default: 17
Low Priority Kernel Work Queue. This lower priority work queue is better suited for more extended, application oriented processing such as file system clean-up, memory garbage collection and asynchronous I/O operations.
Compared to the High Priority Work Queue. The lower priority work queue runs at a lower priority than the high priority work queue, of course, and so is inapproperiate to serve as a driver bottom half. The lower priority work queue has the other advantages, however, that make it better suited for some tasks:
Priority Inheritance. The lower priority worker thread(s) support priority inheritance (if <config> CONFIG_PRIORITY_INHERITANCE is also selected): The priority of the lower priority worker thread can then be adjusted to match the highest priority client.
NOTE: This priority inheritance feature is not automatic. The lower priority worker thread will always a fixed priority unless additional logic implements that callslpwork_boostpriority()
to raise the priority of the lower priority worker thread (typically called before scheduling the work) and then calls the matchinglpwork_restorepriority()
when the work is completed (typically called within the work handler at the completion of the work). Currently, only the NuttX asynchronous I/O logic uses this dynamic prioritization feature.
The higher priority worker thread, on the other hand, is intended to serve as the bottom half for device drivers. As a consequence must run at a very high, fixed priority. Typically, it should be the highest priority thread in your system.
Thread Pool. The low-priority work queue can be configured to support multiple, low-priority threads. This is essentially a thread pool that provides multi-threaded servicing of the low-priority work thread. This breaks the strict serialization of the "queue" (and hence, the low-priority work queue is no longer a queue at all).
Multiple worker threads are required to support, for example, I/O operations that stall waiting for input. If there is only a single thread, then the entire low-priority queue processing would stall in such cases. Such behavior is necessary to support asynchronous I/O, AIO, for example.
Configuration Options.
CONFIG_SCHED_LPWORK
.
If CONFIG_SCHED_LPWORK is selected then a lower-priority work queue will be enabled.
CONFIG_SCHED_LPNTHREADS
.
The number of thread in the low-priority queue's thread pool. Default: 1
CONFIG_SCHED_LPWORKPRIORITY
.
The minimum execution priority of the lower priority worker thread. The priority of the all worker threads start at this priority. If priority inheritance is in effect, the priority may be boosted from this level. Default: 50.
CONFIG_SCHED_LPWORKPRIOMAX
.
The maximum execution priority of the lower priority worker thread. Lower priority worker threads will be started at CONFIG_SCHED_LPWORKPRIORITY
but their priority may be boosted due to priority inheritance. The boosted priority of the low priority worker thread will not, however, ever exceedCONFIG_SCHED_LPWORKPRIOMAX
. This limit would be necessary, for example, if the higher priority worker thread were to defer work to the lower priority thread. Clearly, in such a case, you would want to limit the maximum priority of the lower priority work thread. Default: 176.
CONFIG_SCHED_LPWORKPERIOD
.
How often the lower priority worker thread checks for garbage collection in units of microseconds. Default: 50*1000 (50 MS).
CONFIG_SCHED_LPWORKSTACKSIZE
.
The stack size allocated for the lower priority worker thread. Default: 2048.
Work Queue Accessibility. The high- and low-priority worker threads are kernel-mode threads. In the normal, flat NuttX build, these work queues are are useful to application code and may be shared. However, in the NuttX protected and kernel build modes, kernel mode code is isolated and cannot be accessed from user-mode code.
User-Mode Work Queue.
if either CONFIG_BUILD_PROTECTED
or CONFIG_BUILD_KERNEL
are selected, then the option to enable a special user-mode work queue is enable. The interface to the user-mode work queue is identical to the interface to the kernel-mode work queues and the user-mode work queue is functionally equivalent to the high priority work queue. It differs in that its implementation does not depend on internal, kernel-space facilities.
Configuration Options.
CONFIG_LIB_USRWORK
.
If CONFIG_LIB_USRWORK is also defined then the user-mode work queue will be enabled.
CONFIG_LIB_USRWORKPRIORITY
.
The execution priority of the user-mode priority worker thread. Default: 100
CONFIG_LIB_USRWORKPERIOD
How often the lower priority worker thread is awakened in units of microseconds. Default: 100*1000 (100 MS).
CONFIG_LIB_USRWORKSTACKSIZE
.
The stack size allocated for the lower priority worker thread. Default: 2048.
Work queue IDs. All work queues use the identical interface functions (at least identical in terms of the function signature). The first parameter passed to the work queue interface function identifies the work queue:
Kernel-Mode Work Queue IDs:
HPWORK
.
This ID of the high priority work queue that should only be used for hi-priority, time-critical, driver bottom-half functions.
LPWORK
.
This is the ID of the low priority work queue that can be used for any purpose. if CONFIG_SCHED_LPWORK
is not defined, then there is only one kernel work queue and LPWORK
is equal to HPWORK
.
User-Mode Work Queue IDs:
USRWORK
.
This is the ID of the user-mode work queue that can be used for any purpose by applications. In a flat build, LPWORK
is equal to LPWORK
so that user applications will use the lower priority work queue (if there is one).
typedef void (*worker_t)(FAR void *arg);
Defines the type of the work callback.
struct work_s
.
Defines one entry in the work queue. This is a client-allocated structure. Work queue clients should not reference any field in this structure since they are subjec to change. The user only needs this structure in order to declare instances of the work structure. Handling of all fields is performed by the work queue interfaces described below.
work_queue()
Function Prototype:
#include <nuttx/wqueue.h> int work_queue(int qid, FAR struct work_s *work, worker_t worker, FAR void *arg, uint32_t delay);
Description. Queue work to be performed at a later time. All queued work will be performed on the worker thread of execution (not the caller's).
The work structure is allocated by caller, but completely managed by the work queue logic. The caller should never modify the contents of the work queue structure; the caller should not call work_queue()
again until either (1) the previous work has been performed and removed from the queue, or (2) work_cancel()
has been called to cancel the work and remove it from the work queue.
Input Parameters:
qid
:
The work queue ID.
work
:
The work structure to queue
worker
:
The worker callback to be invoked. The callback will invoked on the worker thread of execution.
arg
:
The argument that will be passed to the worker callback function when it is invoked.
delay
:
Delay (in system clock ticks) from the time queue until the worker is invoked. Zero means to perform the work immediately.
Returned Value:
Zero is returned on success; a negated errno
is returned on failure.
work_cancel()
Function Prototype: #include <nuttx/wqueue.h> int work_cancel(int qid, FAR struct work_s *work);
Description.
Cancel previously queued work. This removes work from the work queue. After work has been cancelled, it may be re-queue by calling work_queue()
again.
Input Parameters:
qid
:
The work queue ID.
work
:
The previously queue work structure to cancel.
Returned Value:
Zero is returned on success; a negated errno
is returned on failure.
ENOENT
: There is no such work queued.EINVAL
: An invalid work queue was specified.work_signal()
Function Prototype: #include <nuttx/wqueue.h> int work_signal(int qid);
Description. Signal the worker thread to process the work queue now. This function is used internally by the work logic but could also be used by the user to force an immediate re-assessment of pending work.
Input Parameters:
qid
:
The work queue ID.
Returned Value:
Zero is returned on success; a negated errno
is returned on failure.
work_available()
Function Prototype:
#include <nuttx/wqueue.h> bool work_available(FAR struct work_s *work);
Description.
Input Parameters: Check if the work structure is available.
work
:
The work queue structure to check.
Returned Value:
true
if available; false if busy
(i.e., there is still pending work).
work_usrstart()
Function Prototype:
#include <nuttx/config.h> #include <nuttx/wqueue.h> #if defined(CONFIG_LIB_USRWORK) && !defined(__KERNEL__) int work_usrstart(void); #endif
Description. The function is only available as a user interface in the kernel-mode build. In the flat build, there is no user-mode work queue; in the protected mode, the user-mode work queue will automatically be started by the OS start-up code. But in the kernel mode, each user process will be required to start is own, private instance of the user-mode work thread using this interface.
Input Parameters: None
Returned Value:
The task ID of the worker thread is returned on success. A negated errno
value is returned on failure.
lpwork_boostpriority()
Function Prototype:
#include <nuttx/config.h> #include <nuttx/wqueue.h> #if defined(CONFIG_SCHED_LPWORK) && defined(CONFIG_PRIORITY_INHERITANCE) void lpwork_boostpriority(uint8_t reqprio); #endif
Description.
Called by the work queue client to assure that the priority of the low-priority worker thread is at least at the requested level, reqprio
. This function would normally be called just before calling work_queue()
.
Input Parameters:
reqprio
:
Requested minimum worker thread priority.
Returned Value: None
lpwork_restorepriority()
Function Prototype:
#include <nuttx/config.h> #include <nuttx/wqueue.h> #if defined(CONFIG_SCHED_LPWORK) && defined(CONFIG_PRIORITY_INHERITANCE) void lpwork_restorepriority(uint8_t reqprio); #endif
Description. This function is called to restore the priority after it was previously boosted. This is often done by client logic on the worker thread when the scheduled work completes. It will check if we need to drop the priority of the worker thread.
Input Parameters:
reqprio
:
Previously requested minimum worker thread priority to be "unboosted".
Returned Value: None
CPUs that support memory management units (MMUs) may provide address environments within which tasks and their child threads execute.
The configuration indicates the CPUs ability to support address environments by setting the configuration variable CONFIG_ARCH_HAVE_ADDRENV=y
.
That will enable the selection of the actual address evironment support which is indicated by the selection of the configuration variable CONFIG_ARCH_ADDRENV=y
.
These address environments are created only when tasks are created via exec()
or exec_module()
(see include/nuttx/binfmt/binfmt.h
).
When CONFIG_ARCH_ADDRENV=y
is set in the board configuration, the CPU-specific logic must provide a set of interfaces as defined in the header file include/nuttx/arch.h
.
These interfaces are listed below and described in detail in the following paragraphs.
The CPU-specific logic must provide two categories in interfaces:
Binary Loader Support.
These are low-level interfaces used in binfmt/
to instantiate tasks with address environments.
These interfaces all operate on type group_addrenv_t
which is an abstract representation of a task group's address environment and the type must be defined inarch/arch.h
if CONFIG_ARCH_ADDRENV
is defined. These low-level interfaces include:
up_addrenv_create()
:
Create an address environment.
up_addrenv_destroy()
:
Destroy an address environment.
up_addrenv_vtext()
:
Returns the virtual base address of the .text
address environment.
up_addrenv_vdata()
:
Returns the virtual base address of the .bss
/.data
address environment.
up_addrenv_heapsize()
:
Return the initial heap size.
up_addrenv_select()
:
Instantiate an address environment.
up_addrenv_restore()
:
Restore an address environment.
up_addrenv_clone()
:
Copy an address environment from one location to another.
Tasking Support.
Other interfaces must be provided to support higher-level interfaces used by the NuttX tasking logic.
These interfaces are used by the functions in sched/
and all operate on the task group which as been assigned an address environment by up_addrenv_clone()
.
up_addrenv_attach()
:
Clone the group address environment assigned to a new thread.
This operation is done when a pthread is created that share's the same address environment.
up_addrenv_detach()
:
Release the thread's reference to a group address environment when a task/thread exits.
Dynamic Stack Support.
CONFIG_ARCH_STACK_DYNAMIC=y
indicates that the user process stack resides in its own address space.
This option is also required if CONFIG_BUILD_KERNEL
and CONFIG_LIBC_EXECFUNCS
are selected.
Why?
Because the caller's stack must be preserved in its own address space when we instantiate the environment of the new process in order to initialize it.
NOTE: The naming of the CONFIG_ARCH_STACK_DYNAMIC
selection implies that dynamic stack allocation is supported.
Certainly this option must be set if dynamic stack allocation is supported by a platform.
But the more general meaning of this configuration environment is simply that the stack has its own address space.
If CONFIG_ARCH_STACK_DYNAMIC=y
is selected then the platform specific code must export these additional interfaces:
up_addrenv_ustackalloc()
:
Create a stack address environment
up_addrenv_ustackfree()
:
Destroy a stack address environment.
up_addrenv_vustack()
:
Returns the virtual base address of the stack
up_addrenv_ustackselect()
:
Instantiate a stack address environment
If CONFIG_ARCH_KERNEL_STACK
is selected, then each user process will have two stacks: (1) a large (and possibly dynamic) user stack and (2) a smaller kernel stack. However, this option is required if both CONFIG_BUILD_KERNEL
and CONFIG_LIBC_EXECFUNCS
are selected. Why? Because when we instantiate and initialize the address environment of the new user process, we will temporarily lose the address environment of the old user process, including its stack contents. The kernel C logic will crash immediately with no valid stack in place.
If CONFIG_ARCH_KERNEL_STACK=y
is selected then the platform specific code must export these additional interfaces:
up_addrenv_kstackalloc()
:
Allocate the process kernel stack.
up_addrenv_kstackfree()
:
Free the process kernel stack.
up_addrenv_create()
Function Prototype:
int up_addrenv_create(size_t textsize, size_t datasize, size_t heapsize, FAR group_addrenv_t *addrenv);
Description:
up_addrenv_create()
is essentially the allocator of the physical memory for the new task.
Input Parameters:
textsize
: The size (in bytes) of the .text
address environment needed by the task. This region may be read/execute only.datasize
: The size (in bytes) of the .bss/.data
address environment needed by the task. This region may be read/write only.heapsize
: The initial size (in bytes) of the heap address environment needed by the task. This region may be read/write only.addrenv
: The location to return the representation of the task address environment.Returned Value:
OK
) on success; a negated errno
value on failure.
up_addrenv_destroy()
Function Prototype:
int up_addrenv_destroy(group_addrenv_t *addrenv);
Description:
up_addrenv_create()
.
Input Parameters:
addrenv
: The representation of the task address environment previously returned by up_addrenv_create()
.Returned Value:
OK
) on success; a negated errno
value on failure.
up_addrenv_vtext()
Function Prototype:
int up_addrenv_vtext(FAR group_addrenv_t addrenv, FAR void **vtext);
Description:
.text
address associated with the newly create address environment.
This function is used by the binary loaders in order get an address that can be used to initialize the new task.
Input Parameters:
addrenv
: The representation of the task address environment previously returned by up_addrenv_create()
.vtext
: The location to return the virtual address.Returned Value:
OK
) on success; a negated errno
value on failure.
up_addrenv_vdata()
Function Prototype:
int up_addrenv_vdata(FAR group_addrenv_t *addrenv, size_t textsize, FAR void **vdata);
Description:
.text
address associated with the newly create address environment.
This function is used by the binary loaders in order get an address that can be used to initialize the new task.
Input Parameters:
addrenv
: The representation of the task address environment previously returned by up_addrenv_create()
.textsize
: For some implementations, the text and data will be saved in the same memory region (read/write/execute) and, in this case, the virtual address of the data just lies at this offset into the common region.vdata
: The location to return the virtual address.Returned Value:
OK
) on success; a negated errno
value on failure.
up_addrenv_heapsize()
Function Prototype:
ssize_t up_addrenv_heapsize(FAR const group_addrenv_t *addrenv);
Description:
up_addrenv_create()
when the heap memory region was first created.
This may or may not differ from the heapsize
parameter that was passed to up_addrenv_create()
.
Input Parameters:
addrenv
: The representation of the task address environment previously returned by up_addrenv_create()
.Returned Value:
errno
value on failure.
up_addrenv_select()
Function Prototype:
int up_addrenv_select(group_addrenv_t *addrenv, save_addrenv_t *oldenv);
Description:
up_addrenv_create())
, this function may be called to to instantiate that address environment in the virtual address space.
This might be necessary, for example, to load the code for the task from a file or to access address environment private data.
Input Parameters:
addrenv
: The representation of the task address environment previously returned by up_addrenv_create()
.oldenv
:
The address environment that was in place before up_addrenv_select()
was called.
This may be used with up_addrenv_restore()
to restore the original address environment that was in place before up_addrenv_select()
was called.
Note that this may be a task agnostic, platform-specific representation that may or may not be different from group_addrenv_t
.
Returned Value:
OK
) on success; a negated errno
value on failure.
up_addrenv_restore()
Function Prototype:
int up_addrenv_restore(save_addrenv_t oldenv);
Description:
up_addrenv_select
,
this function may be called to to restore the original address environment.
Input Parameters:
oldenv
: The platform-specific representation of the address environment previously returned by up_addrenv_select()
.Returned Value:
OK
) on success; a negated errno
value on failure.
up_addrenv_clone()
Function Prototype:
int up_addrenv_clone(FAR const task_group_s *src, FAR struct task_group_s *dest);
Description:
Input Parameters:
src
: The address environment to be copied.dest
: The location to receive the copied address environment.Returned Value:
OK
) on success; a negated errno
value on failure.
up_addrenv_attach()
Function Prototype:
int up_addrenv_attach(FAR struct task_group_s *group, FAR struct tcb_s *tcb);
Description:
This function is called from the core scheduler logic when a thread is created that needs to share the address environment of its task group. In this case, the group's address environment may need to be "cloned" for the child thread.
NOTE: In most platforms, nothing will need to be done in this case. Simply being a member of the group that has the address environment may be sufficient.
Input Parameters:
group
: The task group to which the new thread belongs.ctcb
: The TCB of the thread needing the address environment.Returned Value:
OK
) on success; a negated errno
value on failure.
up_addrenv_detach()
Function Prototype:
int up_addrenv_detach(FAR struct task_group_s *group, FAR struct task_group_s *tcb);
Description:
Input Parameters:
group
: The group to which the thread belonged.tcb
: The TCB of the task or thread whose the address environment will be released.Returned Value:
OK
) on success; a negated errno
value on failure.
up_addrenv_ustackalloc()
Function Prototype:
int up_addrenv_ustackalloc(FAR struct tcb_s *tcb, size_t stacksize);
Description:
This function is called when a new thread is created in order to instantiate an address environment for the new thread's stack.
up_addrenv_ustackalloc()
is essentially the allocator of the physical memory for the new task's stack.
Input Parameters:
tcb
: The TCB of the thread that requires the stack address environment.stacksize
: The size (in bytes) of the initial stack address environment needed by the task. This region may be read/write only.Returned Value:
OK
) on success; a negated errno
value on failure.
up_addrenv_ustackfree()
Function Prototype:
int up_addrenv_ustackfree(FAR struct tcb_s *tcb);
Description:
This function is called when any thread exits. This function then destroys the defunct address environment for the thread's stack, releasing the underlying physical memory.
Input Parameters:
tcb
: The TCB of the thread that no longer requires the stack address environment.Returned Value:
OK
) on success; a negated errno
value on failure.
up_addrenv_vustack()
Function Prototype:
int up_addrenv_vustack(FAR const struct tcb_s *tcb, FAR void **vstack);
Description:
Return the virtual address associated with the newly create stack address environment.
Input Parameters:
tcb
:The TCB of the thread with the stack address environment of interest. vstack
: The location to return the stack virtual base address.Returned Value:
OK
) on success; a negated errno
value on failure.
up_addrenv_ustackselect()
Function Prototype:
int up_addrenv_ustackselect(FAR const struct tcb_s *tcb);
Description:
After an address environment has been established for a task's stack (via up_addrenv_ustackalloc()
.
This function may be called to instantiate that address environment in the virtual address space.
This is a necessary step before each context switch to the newly created thread (including the initial thread startup).
Input Parameters:
tcb
: The TCB of the thread with the stack address environment to be instantiated.Returned Value:
OK
) on success; a negated errno
value on failure.
up_addrenv_kstackalloc()
Function Prototype:
int up_addrenv_kstackalloc(FAR struct tcb_s *tcb);
Description:
This function is called when a new thread is created to allocate the new thread's kernel stack. This function may be called for certain terminating threads which have no kernel stack. It must be tolerant of that case.
Input Parameters:
tcb
: The TCB of the thread that requires the kernel stack.Returned Value:
OK
) on success; a negated errno
value on failure.
up_addrenv_kstackfree()
Function Prototype:
int up_addrenv_kstackfree(FAR struct tcb_s *tcb);
Description:
This function is called when any thread exits. This function frees the kernel stack.
Input Parameters:
tcb
: The TCB of the thread that no longer requires the kernel stack.
Returned Value:
OK
) on success; a negated errno
value on failure.
boardctl()
Application InterfaceFunction Prototype:
include <sys/boardctl.h>
int boardctl(unsigned int cmd, uintptr_t arg);
Description:
In a small embedded system, there will typically be a much greater interaction between application and low-level board features.
The canonically correct to implement such interactions is by implementing a character driver and performing the interactions via low level ioctl()
calls.
This, however, may not be practical in many cases and will lead to "correct" but awkward implementations.
boardctl()
is non-standard OS interface to alleviate the problem.
It basically circumvents the normal device driver ioctl()
interlace and allows the application to perform direct IOCTL-like calls to the board-specific logic.
It is especially useful for setting up board operational and test configurations.
NOTE: The other interfaces described in this document are internal OS interface.
boardctl()
is an application interface to the OS.
There is not point, in fact, of using boardctl()
within the OS;
the board interfaces prototyped in include/nuttx/board.h
may be called directly from within the OS.
Application interfaces are described in the NuttX User Guide. This application interface interface is described here only because it is so non-standard and because it is so closely tied to board porting logic.
Input Parameters:
cmd
: Identifies the board command to be executed.
See include/sys/boardctl.h
for the complete list of common board commands.
Provisions are made to support non-common, board-specific commands as well.
arg
: The argument that accompanies the command.
The nature of the argument is determined by the specific command.
Returned Value:
OK
) is returned;
-1 (ERROR
) is returned on failure with the errno
variable to to indicate the nature of the failure.
According to Wikipedia: "Symmetric multiprocessing (SMP) involves a symmetric multiprocessor system hardware and software architecture where two or more identical processors connect to a single, shared main memory, have full access to all I/O devices, and are controlled by a single operating system instance that treats all processors equally, reserving none for special purposes. Most multiprocessor systems today use an SMP architecture. In the case of multi-core processors, the SMP architecture applies to the cores, treating them as separate processors.
"SMP systems are tightly coupled multiprocessor systems with a pool of homogeneous processors running independently, each processor executing different programs and working on different data and with capability of sharing common resources (memory, I/O device, interrupt system and so on) and connected using a system bus or a crossbar."
For a technical description of the NuttX implementation of SMP, see the NuttX SMP Wiki Page.
Noneup_testset()
Function Prototype:
#include <nuttx/spinlock.h> #ifdef CONFIG_SPINLOCK spinlock_t up_testset(volatile FAR spinlock_t *lock); #endif
Description:
Perform and atomic test and set operation on the provided spinlock.
Input Parameters:
lock
: The address of spinlock object.
Returned Value:
The spinlock is always locked upon return.
The value of previous value of the spinlock variable is returned, either SP_LOCKED
if the spinlock was previously locked (meaning that the test-and-set operation failed to obtain the lock) or SP_UNLOCKED
if the spinlock was previously unlocked (meaning that we successfully obtained the lock)
up_cpu_index()
Function Prototype:
#include <nuttx/arch.h> #ifdef CONFIG_SMP int up_cpu_index(void); #else # define up_cpu_index() (0) #endif
Description:
Return an index in the range of 0 through (CONFIG_SMP_NCPUS-1)
that corresponds to the currently executing CPU.
Input Parameters:
Returned Value:
An integer index in the range of 0 through (CONFIG_SMP_NCPUS-1)
that corresponds to the currently executing CPU.
up_cpu_start()
Function Prototype:
#include <nuttx/arch.h> #ifdef CONFIG_SMP int up_cpu_start(int cpu); #endif
Description:
In an SMP configution, only one CPU is initially active (CPU 0). System initialization occurs on that single thread. At the completion of the initialization of the OS, just before beginning normal multitasking, the additional CPUs would be started by calling this function.
Each CPU is provided the entry point to is IDLE task when started.
A TCB for each CPU's IDLE task has been initialized and placed in the CPU's g_assignedtasks[cpu]
list.
A stack has also been allocated and initialized.
The OS initialization logic calls this function repeatedly until each CPU has been started, 1 through (CONFIG_SMP_NCPUS-1)
.
Input Parameters:
cpu
: The index of the CPU being started.
This will be a numeric value in the range of from one to (CONFIG_SMP_NCPUS-1)
).
(CPU 0 is already active).
Returned Value:
Zero (OK
) is returned on success; a negated errno
value on failure.
up_cpu_pause()
Function Prototype:
#include <nuttx/arch.h> #ifdef CONFIG_SMP int up_cpu_pause(int cpu); #endif
Description:
Save the state of the current task at the head of the g_assignedtasks[cpu]
task list and then pause task execution on the CPU.
This function is called by the OS when the logic executing on one CPU needs to modify the state of the g_assignedtasks[cpu]
list for another CPU.
Input Parameters:
cpu
: The index of the CPU to be paused.
This will not be the index of the currently executing CPU.
Returned Value:
Zero (OK
) is returned on success; a negated errno
value on failure.
up_cpu_resume()
Function Prototype:
#include <nuttx/arch.h> #ifdef CONFIG_SMP int up_cpu_resume(int cpu); #endif
Description:
Restart the cpu after it was paused via up_cpu_pause()
, restoring the state of the task at the head of the g_assignedtasks[cpu]
list, and resume normal tasking.
This function is called after up_cpu_pause()
in order resume operation of the CPU after modifying its g_assignedtasks[cpu]
list.
Input Parameters:
cpu
: The index of the CPU being resumed.
This will not be the index of the currently executing CPU.
Returned Value:
Zero (OK
) is returned on success; a negated errno
value on failure.
These are standard interfaces that are exported by the OS for use by the architecture specific logic.
os_start()
To be provided
To be provided
sched_process_timer()
Function Prototype:
#include <nuttx/arch.h> void sched_process_timer(void);
Description.
This function handles system timer events.
The timer interrupt logic itself is implemented in the
architecture specific code, but must call the following OS
function periodically -- the calling interval must be
MSEC_PER_TICK
.
sched_timer_expiration()
Function Prototype:
#include <nuttx/arch.h> void sched_timer_expiration(void);
Description:
Description: ifCONFIG_SCHED_TICKLESS
is defined, then this function is provided by the RTOS base code and called from platform-specific code when the interval timer used to implemented the tick-less OS expires.
Input Parameters:
Returned Value:
Assumptions:
sched_alaram_expiration()
Function Prototype:
#include <nuttx/arch.h> void sched_timer_expiration(void);Description:
Description: ifCONFIG_SCHED_TICKLESS
is defined, then this function is provided by the RTOS base code and called from platform-specific code when the interval timer used to implemented the tick-less OS expires.
Input Parameters:
Returned Value:
Assumptions:
irq_dispatch()
Function Prototype: void irq_dispatch(int irq, FAR void *context);
Description. This function must be called from the architecture- specific logic in order to display an interrupt to the appropriate, registered handling logic.
Shared memory interfaces are only available with the NuttX kernel build (CONFIG_BUILD_KERNEL=y
).
These interfaces support user memory regions that can be shared between multiple user processes.
The user interfaces are provided in the standard header file include/sys/shm.h>
.
All logic to support shared memory is implemented within the NuttX kernel with the exception of two low-level functions that are require to configure the platform-specific MMU resources.
Those interfaces are described below:
up_shmat()
Function Prototype:
#include <nuttx/arch.h> #ifdef CONFIG_MM_SHM int up_shmat(FAR uintptr_t *pages, unsigned int npages, uintptr_t vaddr); #endifDescription:
Input Parameters:
pages
: A pointer to the first element in a array of physical address, each corresponding to one page of memory.
npages
: The number of pages in the list of physical pages to be mapped.
vaddr
: The virtual address corresponding to the beginning of the (contiguous) virtual address region.
Returned Value:
OK
) is returned on success; a negated errno
value is returned on failure.
up_shmdt()
Function Prototype:
#include <nuttx/arch.h> #ifdef CONFIG_MM_SHM int up_shmdt(uintptr_t vaddr, unsigned int npages); #endifDescription:
Input Parameters:
vaddr
: The virtual address corresponding to the beginning of the (contiguous) virtual address region.
npages
: T The number of pages to be unmapped.
Returned Value:
OK
) is returned on success; a negated errno
value is returned on failure.
The NuttX On-Demand Paging feature permits embedded MCUs with some limited RAM space to execute large programs from some non-random access media. If the platform meets certain requirements, then NuttX can provide on-demand paging: It can copy .text from the large program in non-volatile media into RAM as needed to execute a huge program from the small RAM. Design and porting issues for this feature are discussed in a separate document. Please see the NuttX Demand Paging design document for further information.
A board architecture may or may not have LEDs.
If the board does have LEDs, then most architectures provide similar LED support that is enabled when CONFIG_ARCH_LEDS
is selected in the NuttX configuration file.
This LED support is part of architecture-specific logic and is not managed by the core NuttX logic.
However, the support provided by each architecture is sufficiently similar that it can be documented here.
LED-related definitions are provided in two header files:
board.h
that resides
in the <board-name>/include/board.h
file (which is also
linked to include/arch/board/board.h
when the RTOS is configured).
Those definitions are discussed below.
<arch-name>/src/common/up_internal.h
,
but could be at other locations in particular architectures.
These prototypes are discussed below.
The implementation of LED support is very specific to a board architecture. Some boards have several LEDS, others have only one or two. Some have none. Others LED matrices and show alphanumeric data, etc. The NuttX logic does not refer to specific LEDS, rather, it refers to an event to be shown on the LEDS in whatever manner is appropriate for the board; the way that this event is presented depends upon the hardware available on the board.
The model used by NuttX is that the board can show 8 events defined as follows in <board-name>/include/board.h
:
#define LED_STARTED ?? #define LED_HEAPALLOCATE ?? #define LED_IRQSENABLED ?? #define LED_STACKCREATED ?? #define LED_INIRQ ?? #define LED_SIGNAL ?? #define LED_ASSERTION ?? #define LED_PANIC ??
The specific value assigned to each pre-processor variable can be whatever makes the implementation easiest for the board logic. The meaning associated with each definition is as follows:
LED_STARTED
is the value that describes the setting of the LEDs when the LED logic is first initialized.
This LED value is set but never cleared.
LED_HEAPALLOCATE
indicates that the NuttX heap has been configured.
This is an important place in the boot sequence because if the memory is configured wrong, it will probably crash leaving this LED setting.
This LED value is set but never cleared.
LED_IRQSENABLED
indicates that interrupts have been enabled.
Again, during bring-up (or if there are hardware problems), it is very likely that the system may crash just when interrupts are enabled, leaving this setting on the LEDs.
This LED value is set but never cleared.
LED_STACKCREATED
is set each time a new stack is created.
If set, it means that the system attempted to start at least one new thread.
This LED value is set but never cleared.
LED_INIRQ
is set and cleared on entry and exit from each interrupt.
If interrupts are working okay, this LED will have a dull glow.
LED_SIGNAL
is set and cleared on entry and exit from a signal handler.
Signal handlers are tricky so this is especially useful during bring-up or a new architecture.
LED_ASSERTION
is set if an assertion occurs.
LED_PANIC
will blink at around 1Hz if the system panics and hangs.
The include/nuttx/board.h
has declarations like:
#ifdef CONFIG_ARCH_LEDS void board_autoled_initialize(void); void board_autoled_on(int led); void board_autoled_off(int led); #else # define board_autoled_initialize() # define board_autoled_on(led) # define board_autoled_off(led) #endif
Where:
void board_autoled_initialize(void)
is called early in power-up initialization to initialize the LED hardware.
NOTE: In most architectures, board_autoled_initialize()
is called from board-specific initialization logic.
But there are a few architectures where this initialization function is still called from common chip architecture logic.
This interface is nott, however, a common board interface in any event.
WARNING: This interface name will eventually be removed; do not use it in new board ports.
New implementations should not use the naming convention for common board interfaces, but should instted use the naming conventions for microprocessor-specific interfaces or the board-specific interfaces (such as stm32_led_initialize()
).
board_autoled_on(int led)
is called to instantiate the LED presentation of the event.
The led
argument is one of the definitions provided in <board-name>/include/board.h
.
board_autoled_off(int led
is called to terminate the LED presentation of the event.
The led
argument is one of the definitions provided in <board-name>/include/board.h
.
Note that only LED_INIRQ
, LED_SIGNAL
, LED_ASSERTION
, and LED_PANIC
indications are terminated.
5.0 NuttX File System |
Overview. NuttX includes an optional, scalable file system. This file-system may be omitted altogether; NuttX does not depend on the presence of any file system.
Pseudo Root File System.
Or, a simple in-memory, pseudo file system can be enabled.
This simple file system can be enabled setting the CONFIG_NFILE_DESCRIPTORS
option to a non-zero value (see Appendix A).
This is an in-memory file system because it does not require any
storage medium or block driver support.
Rather, file system contents are generated on-the-fly as referenced via
standard file system operations (open, close, read, write, etc.).
In this sense, the file system is pseudo file system (in the
same sense that the Linux /proc
file system is also
referred to as a pseudo file system).
Any user supplied data or logic can be accessed via the pseudo-file system.
Built in support is provided for character and block drivers in the
/dev
pseudo file system directory.
Mounted File Systems
The simple in-memory file system can be extended my mounting block
devices that provide access to true file systems backed up via some
mass storage device.
NuttX supports the standard mount()
command that allows
a block driver to be bound to a mountpoint within the pseudo file system
and to a file system.
At present, NuttX supports the standard VFAT and ROMFS file systems,
a special, wear-leveling NuttX FLASH File System (NXFFS),
as well as a Network File System client (NFS version 3, UDP).
Comparison to Linux From a programming perspective, the NuttX file system appears very similar to a Linux file system. However, there is a fundamental difference: The NuttX root file system is a pseudo file system and true file systems may be mounted in the pseudo file system. In the typical Linux installation by comparison, the Linux root file system is a true file system and pseudo file systems may be mounted in the true, root file system. The approach selected by NuttX is intended to support greater scalability from the very tiny platform to the moderate platform.
6.0 NuttX Device Drivers |
NuttX supports a variety of device drivers including:
Character device drivers have these properties:
include/nuttx/fs/fs.h
.
All structures and APIs needed to work with character drivers are provided in this header file.
struct file_operations
.
Each character device driver must implement an instance of struct file_operations
.
That structure defines a call table with the following methods:
int open(FAR struct file *filep);
int close(FAR struct file *filep);
ssize_t read(FAR struct file *filep, FAR char *buffer, size_t buflen);
ssize_t write(FAR struct file *filep, FAR const char *buffer, size_t buflen);
off_t seek(FAR struct file *filep, off_t offset, int whence);
int ioctl(FAR struct file *filep, int cmd, unsigned long arg);
int poll(FAR struct file *filep, struct pollfd *fds, bool setup);
int register_driver(const char *path, const struct file_operations *fops, mode_t mode, void *priv);
.
Each character driver registers itself by calling register_driver()
, passing it the
path
where it will appear in the pseudo-file-system and it's
initialized instance of struct file_operations
.
User Access.
After it has been registered, the character driver can be accessed by user code using the standard
driver operations including
open()
, close()
, read()
, write()
, etc.
Specialized Character Drivers. Within the common character driver framework, there are different specific varieties of specialized character drivers. The unique requirements of the underlying device hardware often mandates some customization of the character driver. These customizations tend to take the form of:
ioctl()
commands used to performed specialized operations on the device.
These ioctl()
will be documented in header files under include/nuttx
that detail the specific device interface.
read()
and/or write()
operations use data conforming to a specific format, rather than a plain stream of bytes.
These specialized I/O formats will be documented in header files under include/nuttx
that detail the specific device interface.
The typical representation of the I/O format will be a C structure definition.
The specialized character drivers support by NuttX are documented in the following paragraphs.
Examples:
drivers/dev_null.c
, drivers/fifo.c
, drivers/serial.c
, etc.
include/nuttx/serial/serial.h
.
All structures and APIs needed to work with serial drivers are provided in this header file.
struct uart_ops_s
.
Each serial device driver must implement an instance of struct uart_ops_s
.
That structure defines a call table with the following methods:
int setup(FAR struct uart_dev_s *dev);
void shutdown(FAR struct uart_dev_s *dev);
int attach(FAR struct uart_dev_s *dev);
void detach(FAR struct uart_dev_s *dev);
int ioctl(FAR struct file *filep, int cmd, unsigned long arg);
int receive(FAR struct uart_dev_s *dev, unsigned int *status);
void rxint(FAR struct uart_dev_s *dev, bool enable);
bool rxavailable(FAR struct uart_dev_s *dev);
#ifdef CONFIG_SERIAL_IFLOWCONTROL
bool rxflowcontrol(FAR struct uart_dev_s *dev, unsigned int nbuffered, bool upper);
#endif
void send(FAR struct uart_dev_s *dev, int ch);
void txint(FAR struct uart_dev_s *dev, bool enable);
bool txready(FAR struct uart_dev_s *dev);
bool txempty(FAR struct uart_dev_s *dev);
int uart_register(FAR const char *path, FAR uart_dev_t *dev);
.
A serial driver may register itself by calling uart_register()
, passing it the
path
where it will appear in the pseudo-file-system and it's
initialized instance of struct uart_ops_s
.
By convention, serial device drivers are registered at paths like /dev/ttyS0
, /dev/ttyS1
, etc.
See the uart_register()
implementation in drivers/serial.c
.
User Access. Serial drivers are, ultimately, normal character drivers and are accessed as other character drivers.
Examples:
arch/arm/src/chip/lm_serial.c
, arch/arm/src/lpc214x/lpc214x_serial.c
, arch/z16/src/z16f/z16f_serial.c
, etc.
NuttX supports a two-part touchscreen driver architecture.
Files supporting the touchscreen controller (TSC) driver can be found in the following locations:
include/nuttx/include/input
directory.
The interface between the touchscreen controller "upper half" and "lower half" drivers are not common, but vary from controller-to-controller.
Because of this, each touchscreen driver has its own unique header file that describes the "upper half"/"lower half" interface in that directory.
The application level interface to each touchscreen driver, on the other hand, is the same for each touchscreen driver and is described include/nuttx/include/input/touchscreen.h
.
The touchscreen driver uses a standard character driver framework but read operations return specially formatted data.
drivers/input
.
arch/
<architecture>/src/
<chip> directory for the processor architectures that have build in touchscreen controllers or (2) the configs/
<board>/src/
directory for boards that use an external touchscreen controller chip.
The NuttX analog drivers are split into two parts:
include/nuttx/analog/
.
These header files includes both the application level interface to the analog driver as well as the interface between the "upper half" and "lower half" drivers.
drivers/analog/
.
arch/
<architecture>/src/
<chip> directory for the specific processor <architecture> and for the specific <chip> analog peripheral devices.
include/nuttx/analog/adc.h
.
All structures and APIs needed to work with ADC drivers are provided in this header file.
This header file includes:
drivers/analog/adc.c
.
The implementation of the common ADC character driver.
include/nuttx/analog/dac.h
.
All structures and APIs needed to work with DAC drivers are provided in this header file.
This header file includes:
drivers/analog/dac.c
.
The implementation of the common DAC character driver.
For the purposes of this driver, a PWM device is any device that generates periodic output pulses of controlled frequency and pulse width. Such a device might be used, for example, to perform pulse-width modulated output or frequency/pulse-count modulated output (such as might be needed to control a stepper motor).
The NuttX PWM driver is split into two parts:
Files supporting PWM can be found in the following locations:
include/nuttx/pwm.h
.
This header file includes both the application level interface to the PWM driver as well as the interface between the "upper half" and "lower half" drivers.
The PWM module uses a standard character driver framework.
However, since the PWM driver is a devices control interface and not a data transfer interface,
the majority of the functionality available to the application is implemented in driver ioctl calls.
drivers/pwm.c
.
arch/
<architecture>/src/
<chip> directory for the specific processor <architecture> and for the specific <chip> PWM peripheral devices.
NuttX supports only a very low-level CAN driver. This driver supports only the data exchange and does not include any high-level CAN protocol. The NuttX CAN driver is split into two parts:
Files supporting CAN can be found in the following locations:
include/nuttx/can.h
.
This header file includes both the application level interface to the CAN driver as well as the interface between the "upper half" and "lower half" drivers.
The CAN module uses a standard character driver framework.
drivers/can.c
.
arch/
<architecture>/src/
<chip> directory for the specific processor <architecture> and for the specific <chip> CAN peripheral devices.
NuttX supports a low-level, two-part Quadrature Encoder driver.
Files supporting the Quadrature Encoder can be found in the following locations:
include/nuttx/sensors/qencoder.h
.
This header file includes both the application level interface to the Quadrature Encoder driver as well as the interface between the "upper half" and "lower half" drivers.
The Quadrature Encoder module uses a standard character driver framework.
drivers/sensors/qencoder.c
.
arch/
<architecture>/src/
<chip> directory for the specific processor <architecture> and for the specific <chip> Quadrature Encoder peripheral devices.
NuttX supports a low-level, two-part timer driver.
Files supporting the timer driver can be found in the following locations:
include/nuttx/timers/timer.h
.
This header file includes both the application level interface to the timer driver as well as the interface between the "upper half" and "lower half" drivers.
The timer driver uses a standard character driver framework.
drivers/timers/timer.c
.
arch/
<architecture>/src/
<chip> directory for the specific processor <architecture> and for the specific <chip> timer peripheral devices.
NuttX supports a low-level, two-part RealTime Clock (RTC) driver.
Files supporting the RTC driver can be found in the following locations:
include/nuttx/timers/rtc.h
.
This header file includes both the application level interface to the RTC driver as well as the interface between the "upper half" and "lower half" drivers.
The RTC driver uses a standard character driver framework.
drivers/timers/rtc.c
.
arch/
<architecture>/src/
<chip> directory for the specific processor <architecture> and for the specific <chip> RTC peripheral devices.
NuttX supports a low-level, two-part watchdog timer driver.
Files supporting the watchdog timer driver can be found in the following locations:
include/nuttx/timers/watchdog.h
.
This header file includes both the application level interface to the watchdog timer driver as well as the interface between the "upper half" and "lower half" drivers.
The watchdog timer driver uses a standard character driver framework.
drivers/timers/watchdog.c
.
arch/
<architecture>/src/
<chip> directory for the specific processor <architecture> and for the specific <chip> watchdog timer peripheral devices.
Keypads vs. Keyboards Keyboards and keypads are really the same devices for NuttX. A keypad is thought of as simply a keyboard with fewer keys.
Special Commands. In NuttX, a keyboard/keypad driver is simply a character driver that may have an (optional) encoding/decoding layer on the data returned by the character driver. A keyboard may return simple text data (alphabetic, numeric, and punctuation) or control characters (enter, control-C, etc.) when a key is pressed. We can think about this the "normal" keyboard data stream. However, in addition, most keyboards support actions that cannot be represented as text or control data. Such actions include things like cursor controls (home, up arrow, page down, etc.), editing functions (insert, delete, etc.), volume controls, (mute, volume up, etc.) and other special functions. In this case, some special encoding may be required to multiplex the normal text data and special command key press data streams.
Key Press and Release Events Sometimes the time that a key is released is needed by applications as well. Thus, in addition to normal and special key press events, it may also be necessary to encode normal and special key release events.
Encoding/Decoding Layer.
An optional encoding/decoding layer can be used with the basic character driver to encode the keyboard events into the text data stream.
The function interfaces that comprise that encoding/decoding layer are defined in the header file include/nuttx/input/kbd_code.h
.
These functions provide an matched set of (a) driver encoding interfaces, and (b) application decoding interfaces.
Driver Encoding Interfaces. These are interfaces used by the keyboard/keypad driver to encode keyboard events and data.
kbd_press()
Function Prototype:
#include <nuttx/streams.h> #include <nuttx/input/kbd_codec.h> void kbd_press(int ch, FAR struct lib_outstream_s *stream);
Description:
Input Parameters:
ch
: The character to be added to the output stream.
stream
: An instance of lib_outstream_s
to perform the actual low-level put operation.
Returned Value:
kbd_release()
Function Prototype:
#include <nuttx/streams.h> #include <nuttx/input/kbd_codec.h> void kbd_release(uint8_t ch, FAR struct lib_outstream_s *stream);
Description:
Input Parameters:
ch
: The character associated with the key that was released.
stream
: An instance of lib_outstream_s
to perform the actual low-level put operation.
Returned Value:
kbd_specpress()
Function Prototype:
#include <nuttx/streams.h> #include <nuttx/input/kbd_codec.h> void kbd_specpress(enum kbd_keycode_e keycode, FAR struct lib_outstream_s *stream);
Description:
Input Parameters:
keycode
: The command to be added to the output stream.
The enumeration enum kbd_keycode_e keycode
identifies all commands known to the system.
stream
: An instance of lib_outstream_s
to perform the actual low-level put operation.
Returned Value:
kbd_specrel()
Function Prototype:
#include <nuttx/streams.h> #include <nuttx/input/kbd_codec.h> void kbd_specrel(enum kbd_keycode_e keycode, FAR struct lib_outstream_s *stream);
Description:
Input Parameters:
keycode
: The command to be added to the output stream.
The enumeration enum kbd_keycode_e keycode
identifies all commands known to the system.
stream
: An instance of lib_outstream_s
to perform the actual low-level put operation.
Returned Value:
Application Decoding Interfaces. These are user interfaces to decode the values returned by the keyboard/keypad driver.
kbd_decode()
Function Prototype:
#include <nuttx/streams.h> #include <nuttx/input/kbd_codec.h> int kbd_decode(FAR struct lib_instream_s *stream, FAR struct kbd_getstate_s *state, FAR uint8_t *pch);
Description:
Input Parameters:
stream
: An instance of lib_instream_s
to perform the actual low-level get operation.
pch
: The location to save the returned value.
This may be either a normal, character code or a special command (i.e., a value from enum kbd_getstate_s
.
state
: A user provided buffer to support parsing.
This structure should be cleared the first time that kbd_decode()
is called.
Returned Value:
KBD_PRESS
(0):
Indicates the successful receipt of normal, keyboard data.
This corresponds to a keypress event.
The returned value in pch
is a simple byte of text or control data.
KBD_RELEASE
(1):
Indicates a key release event.
The returned value in pch
is the byte of text or control data corresponding to the released key.
KBD_SPECPRESS
(2):
Indicates the successful receipt of a special keyboard command.
The returned value in pch
is a value from enum kbd_getstate_s
.
KBD_SPECREL
(3):
Indicates a special command key release event.
The returned value in pch
is a value from enum kbd_getstate_s
.
KBD_ERROR
(EOF
):
An error has getting the next character (reported by the stream
).
Normally indicates the end of file.
I/O Streams.
Notice the use of the abstract I/O streams in these interfaces.
These stream interfaces are defined in include/nuttx/streams.h
.
Block device drivers have these properties:
include/nuttx/fs/fs.h
.
All structures and APIs needed to work with block drivers are provided in this header file.
struct block_operations
.
Each block device driver must implement an instance of struct block_operations
.
That structure defines a call table with the following methods:
int open(FAR struct inode *inode);
int close(FAR struct inode *inode);
ssize_t read(FAR struct inode *inode, FAR unsigned char *buffer, size_t start_sector, unsigned int nsectors);
ssize_t write(FAR struct inode *inode, FAR const unsigned char *buffer, size_t start_sector, unsigned int nsectors);
int geometry(FAR struct inode *inode, FAR struct geometry *geometry);
int ioctl(FAR struct inode *inode, int cmd, unsigned long arg);
int register_blockdriver(const char *path, const struct block_operations *bops, mode_t mode, void *priv);
.
Each block driver registers itself by calling register_blockdriver()
, passing it the
path
where it will appear in the pseudo-file-system and it's
initialized instance of struct block_operations
.
User Access.
Users do not normally access block drivers directly, rather, they access block drivers
indirectly through the mount()
API.
The mount()
API binds a block driver instance with a file system and with a mountpoint.
Then the user may use the block driver to access the file system on the underlying media.
Example: See the cmd_mount()
implementation in apps/nshlib/nsh_fscmds.c
.
Accessing a Character Driver as a Block Device.
See the loop device at drivers/loop.c
.
Example: See the cmd_losetup()
implementation in apps/nshlib/nsh_fscmds.c
.
Accessing a Block Driver as Character Device.
See the Block-to-Character (BCH) conversion logic in drivers/bch/
.
Example: See the cmd_dd()
implementation in apps/nshlib/nsh_ddcmd.c
.
Examples.
drivers/loop.c
, drivers/mmcsd/mmcsd_spi.c
, drivers/ramdisk.c
, etc.
All device drivers that are accessible to application logic are either: (1) Character device drivers that can be accessed via the standard driver operations (open()
, close()
, read()
, write()
, etc.), or (2) block drivers that can be accessing only as part of mounting a file system or other special use cases as described in the preceding paragraph.
In addition to this, there are also specialized "drivers" that can be used only within the OS logic itself and are not accessible to application logic. These specialized drivers are discussed in the following paragraphs.
include/nuttx/net/netdev.h
.
All structures and APIs needed to work with Ethernet drivers are provided in this header file.
The structure struct net_driver_s
defines the interface and is passed to uIP via
netdev_register()
.
int netdev_register(FAR struct net_driver_s *dev, enum net_lltype_e lltype);
.
Each Ethernet driver registers itself by calling netdev_register()
.
Examples:
drivers/net/dm90x0.c
, arch/drivers/arm/src/c5471/c5471_ethernet.c
, arch/z80/src/ez80/ez80_emac.c
, etc.
include/nuttx/spi/spi.h
.
All structures and APIs needed to work with SPI drivers are provided in this header file.
struct spi_ops_s
.
Each SPI device driver must implement an instance of struct spi_ops_s
.
That structure defines a call table with the following methods:
void lock(FAR struct spi_dev_s *dev);
void select(FAR struct spi_dev_s *dev, enum spi_dev_e devid, bool selected);
uint32_t setfrequency(FAR struct spi_dev_s *dev, uint32_t frequency);
void setmode(FAR struct spi_dev_s *dev, enum spi_mode_e mode);
void setbits(FAR struct spi_dev_s *dev, int nbits);
uint8_t status(FAR struct spi_dev_s *dev, enum spi_dev_e devid);
uint16_t send(FAR struct spi_dev_s *dev, uint16_t wd);
void exchange(FAR struct spi_dev_s *dev, FAR const void *txbuffer, FAR void *rxbuffer, size_t nwords);
int registercallback(FAR struct spi_dev_s *dev, mediachange_t callback, void *arg);
Binding SPI Drivers.
SPI drivers are not normally directly accessed by user code, but are usually bound to another,
higher level device driver.
See for example, int mmcsd_spislotinitialize(int minor, int slotno, FAR struct spi_dev_s *spi)
in drivers/mmcsd/mmcsd_spi.c
.
In general, the binding sequence is:
struct spi_dev_s
from the hardware-specific SPI device driver, and
Examples:
drivers/loop.c
, drivers/mmcsd/mmcsd_spi.c
, drivers/ramdisk.c
, etc.
include/nuttx/i2c/i2c.h
.
All structures and APIs needed to work with I2C drivers are provided in this header file.
struct i2c_ops_s
.
Each I2C device driver must implement an instance of struct i2c_ops_s
.
That structure defines a call table with the following methods:
int transfer(FAR struct i2c_master_s *dev, FAR struct i2c_msg_s *msgs, int count);
Binding I2C Drivers. I2C drivers are not normally directly accessed by user code, but are usually bound to another, higher level device driver. In general, the binding sequence is:
struct i2c_master_s
from the hardware-specific I2C device driver, and
Examples:
arch/z80/src/ez80/ez80_i2c.c
, arch/z80/src/z8/z8_i2c.c
, etc.
include/nuttx/video/fb.h
.
All structures and APIs needed to work with frame buffer drivers are provided in this header file.
struct fb_vtable_s
.
Each frame buffer device driver must implement an instance of struct fb_vtable_s
.
That structure defines a call table with the following methods:
Get information about the video controller configuration and the configuration of each color plane.
int (*getvideoinfo)(FAR struct fb_vtable_s *vtable, FAR struct fb_videoinfo_s *vinfo);
int (*getplaneinfo)(FAR struct fb_vtable_s *vtable, int planeno, FAR struct fb_planeinfo_s *pinfo);
The following are provided only if the video hardware supports RGB color mapping:
int (*getcmap)(FAR struct fb_vtable_s *vtable, FAR struct fb_cmap_s *cmap);
int (*putcmap)(FAR struct fb_vtable_s *vtable, FAR const struct fb_cmap_s *cmap);
The following are provided only if the video hardware supports a hardware cursor:
int (*getcursor)(FAR struct fb_vtable_s *vtable, FAR struct fb_cursorattrib_s *attrib);
int (*setcursor)(FAR struct fb_vtable_s *vtable, FAR struct fb_setcursor_s *settings);
Binding Frame Buffer Drivers. Frame buffer drivers are not normally directly accessed by user code, but are usually bound to another, higher level device driver. In general, the binding sequence is:
struct fb_vtable_s
from the hardware-specific frame buffer device driver, and
Examples:
arch/sim/src/up_framebuffer.c
.
See also the usage of the frame buffer driver in the graphics/
directory.
include/nuttx/lcd/lcd.h
.
Structures and APIs needed to work with LCD drivers are provided in this header file.
This header file also depends on some of the same definitions used for the frame buffer driver as provided in include/nuttx/video/fb.h
.
struct lcd_dev_s
.
Each LCD device driver must implement an instance of struct lcd_dev_s
.
That structure defines a call table with the following methods:
Get information about the LCD video controller configuration and the configuration of each LCD color plane.
int (*getvideoinfo)(FAR struct lcd_dev_s *dev, FAR struct fb_videoinfo_s *vinfo);
int (*getplaneinfo)(FAR struct lcd_dev_s *dev, unsigned int planeno, FAR struct lcd_planeinfo_s *pinfo);
The following are provided only if the video hardware supports RGB color mapping:
int (*getcmap)(FAR struct lcd_dev_s *dev, FAR struct fb_cmap_s *cmap);
int (*putcmap)(FAR struct lcd_dev_s *dev, FAR const struct fb_cmap_s *cmap);
The following are provided only if the video hardware supports a hardware cursor:
int (*getcursor)(FAR struct lcd_dev_s *dev, FAR struct fb_cursorattrib_s *attrib);
int (*setcursor)(FAR struct lcd_dev_s *dev, FAR struct fb_setcursor_s *settings)
Get the LCD panel power status (0: full off - CONFIG_LCD_MAXPOWER
: full on).
On backlit LCDs, this setting may correspond to the backlight setting.
int (*getpower)(struct lcd_dev_s *dev);
Enable/disable LCD panel power (0: full off - CONFIG_LCD_MAXPOWER
: full on).
On backlit LCDs, this setting may correspond to the backlight setting.
int (*setpower)(struct lcd_dev_s *dev, int power);
Get the current contrast setting (0-CONFIG_LCD_MAXCONTRAST) */
int (*getcontrast)(struct lcd_dev_s *dev);
Set LCD panel contrast (0-CONFIG_LCD_MAXCONTRAST)
int (*setcontrast)(struct lcd_dev_s *dev, unsigned int contrast);
Binding LCD Drivers. LCD drivers are not normally directly accessed by user code, but are usually bound to another, higher level device driver. In general, the binding sequence is:
struct lcd_dev_s
from the hardware-specific LCD device driver, and
Examples:
drivers/lcd/nokia6100.c
, drivers/lcd/p14201.c
, configs/sam3u-ek/src/up_lcd.c.
See also the usage of the LCD driver in the graphics/
directory.
include/nuttx/mtd/mtd.h
.
All structures and APIs needed to work with MTD drivers are provided in this header file.
struct mtd_dev_s
.
Each MTD device driver must implement an instance of struct mtd_dev_s
.
That structure defines a call table with the following methods:
Erase the specified erase blocks (units are erase blocks):
int (*erase)(FAR struct mtd_dev_s *dev, off_t startblock, size_t nblocks);
Read/write from the specified read/write blocks:
ssize_t (*bread)(FAR struct mtd_dev_s *dev, off_t startblock, size_t nblocks, FAR uint8_t *buffer);
ssize_t (*bwrite)(FAR struct mtd_dev_s *dev, off_t startblock, size_t nblocks, FAR const uint8_t *buffer);
Some devices may support byte oriented reads (optional). Most MTD devices are inherently block oriented so byte-oriented accesses are not supported. It is recommended that low-level drivers not support read() if it requires buffering.
ssize_t (*read)(FAR struct mtd_dev_s *dev, off_t offset, size_t nbytes, FAR uint8_t *buffer);
Some devices may also support byte oriented writes (optional).
Most MTD devices are inherently block oriented so byte-oriented accesses are not supported.
It is recommended that low-level drivers not support read() if it requires buffering.
This interface is only available if CONFIG_MTD_BYTE_WRITE
is defined.
ssize_t (*write)(FAR struct mtd_dev_s *dev, off_t offset, size_t nbytes, FAR const uint8_t *buffer);
Support other, less frequently used commands:
MTDIOC_GEOMETRY
: Get MTD geometryMTDIOC_XIPBASE:
: Convert block to physical address for eXecute-In-PlaceMTDIOC_BULKERASE
: Erase the entire device
is provided via a single ioctl
method (see include/nuttx/fs/ioctl.h
):
int (*ioctl)(FAR struct mtd_dev_s *dev, int cmd, unsigned long arg);
Binding MTD Drivers. MTD drivers are not normally directly accessed by user code, but are usually bound to another, higher level device driver. In general, the binding sequence is:
struct mtd_dev_s
from the hardware-specific MTD device driver, and
Examples:
drivers/mtd/m25px.c
and drivers/mtd/ftl.c
include/nuttx/sdio.h
.
All structures and APIs needed to work with SDIO drivers are provided in this header file.
struct sdio_dev_s
.
Each SDIO device driver must implement an instance of struct sdio_dev_s
.
That structure defines a call table with the following methods:
Mutual exclusion:
#ifdef CONFIG_SDIO_MUXBUS
int (*lock)(FAR struct sdio_dev_s *dev, bool lock);
#endif
Initialization/setup:
void (*reset)(FAR struct sdio_dev_s *dev);
uint8_t (*status)(FAR struct sdio_dev_s *dev);
void (*widebus)(FAR struct sdio_dev_s *dev, bool enable);
void (*clock)(FAR struct sdio_dev_s *dev, enum sdio_clock_e rate);
int (*attach)(FAR struct sdio_dev_s *dev);
Command/Status/Data Transfer:
int (*sendcmd)(FAR struct sdio_dev_s *dev, uint32_t cmd, uint32_t arg);
int (*recvsetup)(FAR struct sdio_dev_s *dev, FAR uint8_t *buffer, size_t nbytes);
int (*sendsetup)(FAR struct sdio_dev_s *dev, FAR const uint8_t *buffer, size_t nbytes);
int (*cancel)(FAR struct sdio_dev_s *dev);
int (*waitresponse)(FAR struct sdio_dev_s *dev, uint32_t cmd);
int (*recvR1)(FAR struct sdio_dev_s *dev, uint32_t cmd, uint32_t *R1);
int (*recvR2)(FAR struct sdio_dev_s *dev, uint32_t cmd, uint32_t R2[4]);
int (*recvR3)(FAR struct sdio_dev_s *dev, uint32_t cmd, uint32_t *R3);
int (*recvR4)(FAR struct sdio_dev_s *dev, uint32_t cmd, uint32_t *R4);
int (*recvR5)(FAR struct sdio_dev_s *dev, uint32_t cmd, uint32_t *R5);
int (*recvR6)(FAR struct sdio_dev_s *dev, uint32_t cmd, uint32_t *R6);
int (*recvR7)(FAR struct sdio_dev_s *dev, uint32_t cmd, uint32_t *R7);
Event/Callback support:
void (*waitenable)(FAR struct sdio_dev_s *dev, sdio_eventset_t eventset);
sdio_eventset_t (*eventwait)(FAR struct sdio_dev_s *dev, uint32_t timeout);
void (*callbackenable)(FAR struct sdio_dev_s *dev, sdio_eventset_t eventset);
int (*registercallback)(FAR struct sdio_dev_s *dev, worker_t callback, void *arg);
DMA support:
bool (*dmasupported)(FAR struct sdio_dev_s *dev);
int (*dmarecvsetup)(FAR struct sdio_dev_s *dev, FAR uint8_t *buffer, size_t buflen);
int (*dmasendsetup)(FAR struct sdio_dev_s *dev, FAR const uint8_t *buffer, size_t buflen);
Binding SDIO Drivers. SDIO drivers are not normally directly accessed by user code, but are usually bound to another, higher level device driver. In general, the binding sequence is:
struct sdio_dev_s
from the hardware-specific SDIO device driver, and
Examples:
arch/arm/src/stm32/stm32_sdio.c
and drivers/mmcsd/mmcsd_sdio.c
include/nuttx/usb/usbhost.h
.
All structures and APIs needed to work with USB host-side drivers are provided in this header file.
struct usbhost_driver_s
and struct usbhost_connection_s
.
Each USB host controller driver must implement an instance of struct usbhost_driver_s
and struct usbhost_connection_s
:
struct usbhost_driver_s
provides the interface between the USB host driver and the USB class driver;
struct usbhost_connection_s
provides the interface between the USB host driver and platform-specific connection management and device enumeration logic.
These structures are defined in include/nuttx/usb/usbhost.h
.
Examples:
arch/arm/src/lpc17xx/lpc17_usbhost.c
,
arch/arm/src/stm32/stm32_otgfshost.c
,
arch/arm/src/sama5/sam_ohci.c
, and
arch/arm/src/sama5/sam_ehci.c
.
struct usbhost_class_s
.
Each USB host class driver must implement an instance of struct usbhost_class_s
.
This structure is also defined in include/nuttx/usb/usbhost.h
.
Examples:
drivers/usbhost/usbhost_storage.c
USB Host Class Driver Registry.
The NuttX USB host infrastructure includes a registry.
During its initialization, each USB host class driver must call the interface, usbhost_registerclass()
in order add its interface to the registry.
Later, when a USB device is connected, the USB host controller will look up the USB host class driver that is needed to support the connected device in this registry.
Examples:
drivers/usbhost/usbhost_registry.c
, drivers/usbhost/usbhost_registerclass.c
, and drivers/usbhost/usbhost_findclass.c
,
Detection and Enumeration of Connected Devices. Each USB host device controller supports two methods that are used to detect and enumeration newly connected devices (and also detect disconnected devices):
int (*wait)(FAR struct usbhost_connection_s *drvr, FAR const bool *connected);
Wait for a device to be connected or disconnected.
int (*enumerate)(FAR struct usbhost_connection_s *drvr, int rhpndx);
Enumerate the device connected to a root hub port.
As part of this enumeration process, the driver will
(1) get the device's configuration descriptor,
(2) extract the class ID info from the configuration descriptor,
(3) call usbhost_findclass(
) to find the class that supports this device,
(4) call the create()
method on the struct usbhost_registry_s interface
to get a class instance, and
finally (5) call the connect()
method of the struct usbhost_class_s
interface.
After that, the class is in charge of the sequence of operations.
Binding USB Host-Side Drivers.
USB host-side controller drivers are not normally directly accessed by user code,
but are usually bound to another, higher level USB host class driver.
The class driver exports the standard NuttX device interface so that the connected USB device can be accessed just as with other, similar, on-board devices.
For example, the USB host mass storage class driver (drivers/usbhost/usbhost_storage.c
) will register a standard, NuttX block driver interface (like /dev/sda
)
that can be used to mount a file system just as with any other other block driver instance.
In general, the binding sequence is:
Each USB host class driver includes an initialization entry point that is called from the
application at initialization time.
This driver calls usbhost_registerclass()
during this initialization in order to makes itself available in the event the device that it supports is connected.
Examples:
The function usbhost_msc_initialize()
in the file drivers/usbhost/usbhost_storage.c
Each application must include a waiter thread thread that (1) calls the USB host controller driver's wait()
to detect the connection of a device, and then
(2) call the USB host controller driver's enumerate
method to bind the registered USB host class driver to the USB host controller driver.
Examples:
The function nsh_waiter()
in the file configs/olimex-lpc1766stk/src/lpc17_appinit.c
.
As part of its operation during the binding operation, the USB host class driver will register an instances of a standard NuttX driver under the /dev
directory.
To repeat the above example, the USB host mass storage class driver (drivers/usbhost/usbhost_storage.c
) will register a standard, NuttX block driver interface (like /dev/sda
)
that can be used to mount a file system just as with any other other block driver instance.
Examples:
See the call to register_blockdriver()
in the function usbhost_initvolume()
in the file drivers/usbhost/usbhost_storage.c
.
include/nuttx/usb/usbdev.h
.
All structures and APIs needed to work with USB device-side drivers are provided in this header file.
include/nuttx/usb/usbdev_trace.h
.
Declarations needed to work with the NuttX USB device driver trace capability.
That USB trace capability is detailed in separate document.
struct usbdev_s
.
Each USB device controller driver must implement an instance of struct usbdev_s
.
This structure is defined in include/nuttx/usb/usbdev.h
.
Examples:
arch/arm/src/dm320/dm320_usbdev.c
, arch/arm/src/lpc17xx/lpc17_usbdev.c
,
arch/arm/src/lpc214x/lpc214x_usbdev.c
, arch/arm/src/lpc313x/lpc313x_usbdev.c
, and
arch/arm/src/stm32/stm32_usbdev.c
.
struct usbdevclass_driver_s
.
Each USB device class driver must implement an instance of struct usbdevclass_driver_s
.
This structure is also defined in include/nuttx/usb/usbdev.h
.
Examples:
drivers/usbdev/pl2303.c
and drivers/usbdev/usbmsc.c
Binding USB Device-Side Drivers. USB device-side controller drivers are not normally directly accessed by user code, but are usually bound to another, higher level USB device class driver. The class driver is then configured to export the USB device functionality. In general, the binding sequence is:
Each USB device class driver includes an initialization entry point that is called from the application at initialization time.
Examples:
The function usbdev_serialinitialize()
in the file drivers/usbdev/pl2303.c
and
the function in the file
drivers/usbdev/usbmsc.c
These initialization functions called the driver API, usbdev_register()
.
This driver function will bind the USB class driver to the USB device controller driver,
completing the initialization.
Power Management (PM) Sub-System. NuttX supports a simple power management (PM) sub-system. This sub-system:
Monitors activity from drivers (and from other parts of the syste), and
Provides hooks to place drivers (and the whole system) into reduce power modes of operation.
The PM sub-system integrates the MCU idle loop with a collection of device drivers to support:
Reports of relevant driver or other system activity.
Registration and callback mechanism to interface with individual device drivers.
IDLE time polling of overall driver activity.
Coordinated, global, system-wide transitions to lower power usage states.
Low Power Consumption States. Various "sleep" and low power consumption states have various names and are sometimes used in conflicting ways. In the NuttX PM logic, we will use the following terminology:
NORMAL
IDLE
IDLE
and some simple simple steps to reduce power
consumption provided that they do not interfere with normal
Operation. Simply dimming the a backlight might be an example
somethat that would be done when the system is idle.
STANDBY
SLEEP
SLEEP
(some MCUs may even require going through reset).
These various states are represented with type enum pm_state_e
in include/nuttx/power/pm.h
.
Power Management Domains.
Each PM interfaces includes a integer domain number.
By default, only a single power domain is supported (CONFIG_PM_NDOMAINS=1
).
But that is configurable; any number of PM domains can be supported.
Multiple PM domains might be useful, for example, if you would want to control power states associated with a network separately from power states associated with a user interface.
All PM interfaces are declared in the file include/nuttx/power/pm.h
.
pm_initialize()
Function Prototype:
#include <nuttx/power/pm.h> void pm_initialize(void);
Description: This function is called by MCU-specific one-time at power on reset in order to initialize the power management capabilities. This function must be called very early in the initialization sequence before any other device drivers are initialize (since they may attempt to register with the power management subsystem).
Input Parameters: None
Returned Value: None
pm_register()
Function Prototype:
#include <nuttx/power/pm.h> int pm_register(FAR struct pm_callback_s *callbacks);
Description: This function is called by a device driver in order to register to receive power management event callbacks. Refer to the PM Callback section for more details.
Input Parameters:
callbacks
struct pm_callback_s
providing the driver callback functions.
Returned Value:
Zero (OK
) on success; otherwise a negated errno
value is returned.
pm_activity()
Function Prototype:
#include <nuttx/power/pm.h> void pm_activity(int domain, int priority);
Description: This function is called by a device driver to indicate that it is performing meaningful activities (non-idle). This increment an activity count and/or will restart a idle timer and prevent entering reduced power states.
Input Parameters:
domain
priority
Returned Value: None
Assumptions: This function may be called from an interrupt handler (this is the ONLY PM function that may be called from an interrupt handler!).
pm_checkstate()
Function Prototype:
#include <nuttx/power/pm.h> enum pm_state_e pm_checkstate(int domain);
Description:
This function is called from the MCU-specific IDLE loop to monitor the power management conditions.
This function returns the "recommended" power management state based on the PM configuration and activity reported in the last sampling periods.
The power management state is not automatically changed, however.
The IDLE loop must call pm_changestate()
in order to make the state change.
These two steps are separated because the platform-specific IDLE loop may have additional situational information that is not available to the PM sub-system. For example, the IDLE loop may know that the battery charge level is very low and may force lower power states even if there is activity.
NOTE: That these two steps are separated in time and, hence, the IDLE loop could be suspended for a long period of time between calling pm_checkstate()
and pm_changestate()
.
The IDLE loop may need to make these calls atomic by either disabling interrupts until the state change is completed.
Input Parameters:
domain
Returned Value: The recommended power management state.
pm_changestate()
Function Prototype:
#include <nuttx/power/pm.h> int pm_changestate(int domain, enum pm_state_e newstate);
Description: This function is used by platform-specific power management logic. It will announce the power management power management state change to all drivers that have registered for power management event callbacks.
Input Parameters:
domain
newstate
Returned Value:
0 (OK
) means that the callback function for all registered drivers returned OK
(meaning that they accept the state change).
Non-zero means that one of the drivers refused the state change.
In this case, the system will revert to the preceding state.
Assumptions: It is assumed that interrupts are disabled when this function is called. This function is probably called from the IDLE loop... the lowest priority task in the system. Changing driver power management states may result in renewed system activity and, as a result, can suspend the IDLE thread before it completes the entire state change unless interrupts are disabled throughout the state change.
The struct pm_callback_s
includes the pointers to the driver callback functions.
This structure is defined include/nuttx/power/pm.h
.
These callback functions can be used to provide power management information to the driver.
prepare()
Function Prototype:
int (*prepare)(FAR struct pm_callback_s *cb, int domain, enum pm_state_e pmstate);
Description: Request the driver to prepare for a new power state. This is a warning that the system is about to enter into a new power state. The driver should begin whatever operations that may be required to enter power state. The driver may abort the state change mode by returning a non-zero value from the callback function.
Input Parameters:
cb
domain
pmstate
Returned Value:
Zero (OK
) means the event was successfully processed and that the driver is prepared for the PM state change.
Non-zero means that the driver is not prepared to perform the tasks needed achieve this power setting and will cause the state change to be aborted.
NOTE: The prepare()
method will also be called when reverting from lower back to higher power consumption modes (say because another driver refused a lower power state change).
Drivers are not permitted to return non-zero values when reverting back to higher power
consumption modes!
notify()
Function Prototype:
#include <nuttx/power/pm.h> void (*notify)(FAR struct pm_callback_s *cb, int domain, enum pm_state_e pmstate);
Description: Notify the driver of new power state. This callback is called after all drivers have had the opportunity to prepare for the new power state.
Input Parameters:
cb
domain
pmstate
Returned Value:
None.
The driver already agreed to transition to the low power consumption state when when it returned OK
to the prepare()
call.
Appendix A: NuttX Configuration Settings |
At one time, this section provided a list of all NuttX configuration variables.
However, NuttX has since converted to use the kconfig-frontends tools.
Now, the NuttX configuration is determined by a self-documenting set of Kconfig
files.
The current NuttX configuration variables are also documented in separate, auto-generated configuration variable document.
That configuration variable document is generated using the kconfig2html
tool that can be found in the nuttx/tools
directory.
That tool analyzes the NuttX Kconfig files and generates excruciatingly boring HTML document.
The latest boring configuration variable documentation can be regenerated at any time using that tool or, more appropriately, the wrapper script at nuttx/tools/mkconfigvars.sh
.
That script will generate the file nuttx/Documentation/NuttXConfigVariables.html
.
The version of NuttXConfigVariables.html
for the last released version of NuttX can also be found online.
Appendix B: Trademarks |
NOTE: NuttX is not licensed to use the POSIX trademark. NuttX uses the POSIX standard as a development guideline only.