131 lines
4.8 KiB
ReStructuredText
131 lines
4.8 KiB
ReStructuredText
==========================
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Architecture-Specific Code
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==========================
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The NuttX configuration consists of:
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* Processor architecture specific files. These are the files contained
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in the ``arch/<arch-name>/`` directory discussed in this file.
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* Chip/SoC specific files. Each processor architecture is embedded in
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chip or System-on-a-Chip (SoC) architecture. The full chip
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architecture includes the processor architecture plus chip-specific
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interrupt logic, general purpose I/O (GPIO) logic, and specialized,
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internal peripherals (such as UARTs, USB, etc.).
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These chip-specific files are contained within chip-specific
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sub-directories in the ``arch/<arch-name>/`` directory and are selected
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via the CONFIG_ARCH_name selection
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* Board specific files. In order to be usable, the chip must be
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contained in a board environment. The board configuration defines
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additional properties of the board including such things as peripheral
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LEDs, external peripherals (such as network, USB, etc.).
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These board-specific configuration files can be found in the
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``boards/<arch>/<chip>/<board>`` sub-directories.
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This file will address the processor architecture specific files that
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are contained in the ``arch/<arch-name>/`` directory. The file
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include/nuttx/arch.h identifies all of the APIs that must be provided by
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this architecture specific logic. (It also includes
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``arch/<arch-name>/arch.h`` as described below).
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Directory Structure in ``arch/``
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================================
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The ``arch/`` directory contains architecture-specific logic. The complete
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board port is defined by the architecture-specific code in this
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directory plus the board-specific configurations in the ``boards/``
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directory. Each architecture must provide a subdirectory <arch-name>
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under ``arch/`` with the following characteristics::
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<arch-name>/
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|-- include/
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| |--<chip-name>/
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| | `-- (chip-specific header files)
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| |--<other-chips>/
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| |-- arch.h
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| |-- irq.h
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| `-- types.h
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`-- src/
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|--<chip-name>/
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| `-- (chip-specific source files)
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|--<other-chips>/
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|-- Makefile
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`-- (architecture-specific source files)
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Summary of Files
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================
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``include/<chip-name>/``
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This sub-directory contains chip-specific header files.
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``include/arch.h``
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This is a hook for any architecture specific definitions that may be
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needed by the system. It is included by ``include/nuttx/arch.h``
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``include/types.h``
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This provides architecture/toolchain-specific definitions for standard
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types. This file should typedef::
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_int8_t, _uint8_t, _int16_t, _uint16_t, _int32_t, _uint32_t
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and if the architecture supports 64-bit integers::
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_int24_t, _uint24_t, _int64_t, _uint64_t
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NOTE that these type names have a leading underscore character. This
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file will be included (indirectly) by ``include/stdint.h`` and typedef'ed
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to the final name without the underscore character. This roundabout
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way of doings things allows the stdint.h to be removed from the
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``include/`` directory in the event that the user prefers to use the
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definitions provided by their toolchain header files.
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``irqstate_t``
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Must be defined to the size required to hold the interrupt
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enable/disable state.
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This file will be included by ``include/sys/types.h`` and be made
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available to all files.
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``include/irq.h``
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This file needs to define some architecture-specific functions
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(usually inline if the compiler supports inlining) and structures.
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These include:
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``struct xcptcontext``
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This structure represents the saved context ofa thread.
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``irqstate_t up_irq_save(void)``
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Used to disable all interrupts.
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``void up_irq_restore(irqstate_t flags)``
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Used to restore interrupt enables to the same state as before ``up_irq_save``
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was called.
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NOTE: These interfaces are not available to application code but can
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only be used within the operating system code. And, in general, these
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functions should **never** be called directly, not unless you know
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absolutely well what you are doing. Rather you should typically use
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the wrapper functions ``enter_critical_section()`` and
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``leave_critical_section()`` as prototyped in ``include/nuttx/irq.h``.
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This file must also define NR_IRQS, the total number of IRQs supported
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by the board.
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``src/<chip-name>/``
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This sub-directory contains chip-specific source files.
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``src/Makefile``
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This makefile will be executed to build the targets src/libup.a and
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src/up_head.o. The up_head.o file holds the entry point into the
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system (power-on reset entry point, for example). It will be used in
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the final link with libup.a and other system archives to generate the
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final executable.
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Supported Architectures
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=======================
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The list of supported architectures can be found in :ref:`Supported Platforms <platforms>`.
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