Architecture-Specific Code
^^^^^^^^^^^^^^^^^^^^^^^^^^
The file 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 below).
Directory Structure
^^^^^^^^^^^^^^^^^^^
Thie arch directory contains architecture specific logic. Each aructure
provide a a subdirectory <arch-name>under arch/ with the folling characteristics:
<arch-name>
|-- Make.defs
|-- defconfig
|-- setenv.sh
|-- include
| |-- arch.h
| |-- irq.h
| `-- types.h
`-- src
|-- Makefile
`-- (architecture-specific source files)
Summary of 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:
Tools: CC, LD, AR, NM, OBJCOPY, OBJDUMP
Tool options: 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 may include ${TOPDIR}/.config to perform configuration
specific settings. For example, the CFLAGS will most likely be
different if CONFIG_DEBUG=y.
defconfig -- This is a configuration file similar to the Linux
configuration file. In contains varialble/value pairs like:
CONFIG_VARIABLE=value
This configuration file will be used at build time:
(1) as a makefile fragment included in other makefiles, and
(2) to generate include/nuttx/config.h which is included by
most C files in the system.
The following variables are recognized by the build (you may
also include architecture-specific settings).
Architecture selection:
CONFIG_ARCH - identifies the arch subdirectory
CONFIG_ARCH_name - for use in C code
General OS setup
CONFIG_EXAMPLE - identifies the subdirectory in examples
that will be used in the build
CONFIG_DEBUG - enables built-in debug options
CONFIG_DEBUG_VERBOSE - enables verbose debug output
CONFIG_HAVE_LOWPUTC - architecture supports low-level, boot
time console output
CONFIG_RR_INTERVAL - The round robin timeslice will be set
this number of milliseconds; Round robin scheduling can
be disabled by setting this value to zero.
CONFIG_SCHED_INSTRUMENTATION - enables instrumentation in
scheduler to monitor system performance
CONFIG_TASK_NAME_SIZE - Spcifies that maximum size of a
task name to save in the TCB. Useful if scheduler
instrumentation is selected. Set to zero to disable.
CONFIG_START_YEAR, CONFIG_START_MONTH, CONFIG_START_DAY -
Used to initialize the internal time logic.
CONFIG_JULIAN_TIME - Enables Julian time conversions
CONFIG_DEV_CONSOLE - Set if architecture-specific logic
provides /dev/console. Enables stdout, stderr, stdin.
The following can be used to disable categories of APIs supported
by the OS. If the compiler supports weak functions, then it
should not be necessary to disable functions unless you want to
restrict usage of those APIs.
There are certain dependency relationships in these features.
o mq_notify logic depends on signals to awaken tasks
waiting for queues to become full or empty.
o pthread_condtimedwait() depends on signals to wake
up waiting tasks.
CONFIG_DISABLE_SIGNALS, CONFIG_DISABLE_MQUEUE
Allow for architecture optimized implementations
The architecture can provide optimized versions of the
following to improve sysem performance
CONFIG_ARCH_MEMCPY, CONFIG_ARCH_MEMCMP, CONFIG_ARCH_MEMMOVE
CONFIG_ARCH_MEMSET, CONFIG_ARCH_STRCMP, CONFIG_ARCH_STRCPY
CONFIG_ARCH_STRNCPY, CONFIG_ARCH_STRLEN, CONFIG_ARCH_BZERO
CONFIG_ARCH_KMALLOC, CONFIG_ARCH_KZMALLOC, CONFIG_ARCH_KFREE
Sizes of configurable things (0 disables)
CONFIG_NPTHREAD_KEYS - The number of items of thread-
specific data that can be retained
CONFIG_NFILE_DESCRIPTORS - The maximum number of file
descriptors (one for each open)
CONFIG_NFILE_STREAMS - The maximum number of streams that
can be fopen'ed
CONFIG_STDIO_BUFFER_SIZE - Size of the buffer to allocate
on fopen. (Only if CONFIG_NFILE_STREAMS > 0)
CONFIG_NUNGET_CHARS - Number of characters that can be
buffered by ungetc() (Only if CONFIG_NFILE_STREAMS > 0)
CONFIG_PREALLOC_MQ_MSGS - The number of pre-allocated message
structures. The system manages a pool of preallocated
message structures to minimize dynamic allocations
CONFIG_MQ_MAXMSGSIZE - Message structures are allocated with
a fixed payload size given by this settin (does not include
other message structure overhead.
CONFIG_PREALLOC_WDOGS - The number of pre-allocated watchdog
structures. The system manages a pool of preallocated
watchdog structures to minimize dynamic allocations
Stack and heap information
CONFIG_BOOT_FROM_FLASH - Some configurations support XIP
operation from FLASH.
CONFIG_STACK_POINTER - The initial stack pointer
CONFIG_PROC_STACK_SIZE - The size of the initial stack
CONFIG_PTHREAD_STACK_MIN - Minimum pthread stack size
CONFIG_PTHREAD_STACK_DEFAULT - Default pthread stack size
CONFIG_HEAP_BASE - The beginning of the heap
CONFIG_HEAP_SIZE - The size of the heap
setenv.sh -- This is a script that you can include that will be installed at
the toplevel of the directory structure and can be sourced to set any
necessary environment variables.
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:
sbyte, ubyte, uint8, boolean, sint16, uint16, sint32, uint32
and
sint64, uint64
if the architecture supports 64-bit integers.
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 structure. These include:
- struct xcptcontext. This structures represents the saved context
of a thread.
- irqstate_t irqsave(void) -- Used to disable all interrupts.
- void irqrestore(irqstate_t flags) -- Used to restore interrupt
enables to the same state as before irqsave was called.
This file must also define NR_IRQS, the total number of IRQs supported
by the board.
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.
Configuring NuttX
^^^^^^^^^^^^^^^^^
Configuring NuttX requires only copying
arch/<arch-name>/Make.def to ${TOPDIR}/Make.defs
arch/<arch-name>/setenv.sh to ${TOPDIR}/setenv.sh
arch/<arch-name>/defconfig to ${TOPDIR}/.config
There is a script that automates these steps. The following steps will
accomplish the same configuration:
cd tools
./configure.sh <arch-name>
fb61b0b76b