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diff --git a/bsp_howto/target_dependant_files.rst b/bsp_howto/target_dependant_files.rst deleted file mode 100644 index ecc9b3a..0000000 --- a/bsp_howto/target_dependant_files.rst +++ /dev/null @@ -1,229 +0,0 @@ -.. comment SPDX-License-Identifier: CC-BY-SA-4.0 - -.. COMMENT: COPYRIGHT (c) 1988-2008. -.. COMMENT: On-Line Applications Research Corporation (OAR). -.. COMMENT: All rights reserved. - - -Target Dependent Files -###################### - -RTEMS has a multi-layered approach to portability. This is done to maximize the -amount of software that can be reused. Much of the RTEMS source code can be -reused on all RTEMS platforms. Other parts of the executive are specific to -hardware in some sense. RTEMS classifies target dependent code based upon its -dependencies into one of the following categories. - -- CPU dependent - -- Board dependent - -- Peripheral dependent - -CPU Dependent -============= - -This class of code includes the foundation routines for the executive proper -such as the context switch and the interrupt subroutine implementations. -Sources for the supported processor families can be found in -``cpukit/score/cpu``. A good starting point for a new family of processors is -the ``no_cpu`` directory, which holds both prototypes and descriptions of each -needed CPU dependent function. - -CPU dependent code is further subcategorized if the implementation is dependent -on a particular CPU model. For example, the MC68000 and MC68020 processors are -both members of the m68k CPU family but there are significant differences -between these CPU models which RTEMS must take into account. - -The source code found in the ``cpukit/score/cpu`` is required to only depend -upon the CPU model variations that GCC distinguishes for the purposes of -multilib'ing. Multilib is the term the GNU community uses to refer to building -a single library source multiple times with different compiler options so the -binary code generated is compatible. As an example, from GCC's perspective, -many PowerPC CPU models are just a PPC603e. Remember that GCC only cares about -the CPU code itself and need not be aware of any peripherals. In the embedded -community, we are exposed to thousands of CPU models which are all based upon -only a relative small number of CPU cores. - -Similarly for the SPARC/ERC32 BSP, the ``RTEMS_CPU`` is specified as ``erc32`` -which is the name of the CPU model and BSP for this SPARC V7 system on chip. -But the multilib variant used is actually ``v7`` which indicates the ERC32 CPU -core is a SPARC V7. - -Board Dependent -=============== - -This class of code provides the most specific glue between RTEMS and a -particular board. This code is represented by the Board Support Packages and -associated Device Drivers. Sources for the BSPs included in the RTEMS -distribution are located in the directory ``c/src/lib/libbsp``. The BSP source -directory is further subdivided based on the CPU family and BSP. - -Some BSPs may support multiple board models within a single board family. This -is necessary when the board supports multiple variants on a single base board. -For example, the Motorola MVME162 board family has a fairly large number of -variations based upon the particular CPU model and the peripherals actually -placed on the board. - -Peripheral Dependent -==================== - -This class of code provides a reusable library of peripheral device drivers -which can be tailored easily to a particular board. The libchip library is a -collection of reusable software objects that correspond to standard -controllers. Just as the hardware engineer chooses a standard controller when -designing a board, the goal of this library is to let the software engineer do -the same thing. - -The source code for the reusable peripheral driver library may be found in the -directory ``c/src/lib/libchip``. The source code is further divided based upon -the class of hardware. Example classes include serial communications -controllers, real-time clocks, non-volatile memory, and network controllers. - -Questions to Ask -================ - -When evaluating what is required to support RTEMS applications on a particular -target board, the following questions should be asked: - -- Does a BSP for this board exist? - -- Does a BSP for a similar board exists? - -- Is the board's CPU supported? - -If there is already a BSP for the board, then things may already be ready to -start developing application software. All that remains is to verify that the -existing BSP provides device drivers for all the peripherals on the board that -the application will be using. For example, the application in question may -require that the board's Ethernet controller be used and the existing BSP may -not support this. - -If the BSP does not exist and the board's CPU model is supported, then examine -the reusable chip library and existing BSPs for a close match. Other BSPs and -libchip provide starting points for the development of a new BSP. It is often -possible to copy existing components in the reusable chip library or device -drivers from BSPs from different CPU families as the starting point for a new -device driver. This will help reduce the development effort required. - -If the board's CPU family is supported but the particular CPU model on that -board is not, then the RTEMS port to that CPU family will have to be augmented. -After this is done, development of the new BSP can proceed. - -Otherwise both CPU dependent code and the BSP will have to be written. - -This type of development often requires specialized skills and there are people -in the community who provide those services. If you need help in making these -modifications to RTEMS try a search in a search engine with something like -"rtems support". The RTEMS Project encourages users to use support services -however we do not endorse any providers. - -CPU Dependent Executive Files -============================= - -The CPU dependent files in the RTEMS executive source code are found in the -following directory: - -.. code-block:: c - - cpukit/score/cpu/<CPU> - -where <CPU> is replaced with the CPU family name. - -Within each CPU dependent directory inside the executive proper is a file named -``<CPU>.h`` which contains information about each of the supported CPU models -within that family. - -CPU Dependent Support Files -=========================== - -The CPU dependent support files contain routines which aid in the development -of applications using that CPU family. For example, the support routines -may contain standard trap handlers for alignment or floating point exceptions -or device drivers for peripheral controllers found on the CPU itself. -This class of code may be found in the following directory: - -.. code-block:: c - - c/src/lib/libcpu/<CPU> - -CPU model dependent support code is found in the following directory: - -.. code-block:: c - - c/src/lib/libcpu/<CPU>/<CPU_MODEL> - -<CPU_MODEL> may be a specific CPU model name or a name indicating a CPU core or -a set of related CPU models. The file ``configure.ac`` in each -``c/src/lib/libcpu/<CPU>`` directory contains the logic which enables the -appropriate subdirectories for the specific CPU model your BSP has. - -Board Support Package Structure -=============================== - -The BSPs are all under the ``c/src/lib/libbsp`` directory. Below this -directory, there is a subdirectory for each CPU family. Each BSP is found -under the subdirectory for the appropriate processor family (arm, powerpc, -sparc, etc.). In addition, there is source code available which may be shared -across all BSPs regardless of the CPU family or just across BSPs within a -single CPU family. This results in a BSP using the following directories: - -.. code-block:: c - - c/src/lib/libbsp/shared - c/src/lib/libbsp/<CPU>/shared - c/src/lib/libbsp/<CPU>/<BSP> - -Under each BSP specific directory, there is a collection of subdirectories. -For commonly provided functionality, the BSPs follow a convention on -subdirectory naming. The following list describes the commonly found -subdirectories under each BSP. - -- ``console``: - is technically the serial driver for the BSP rather than just a console - driver, it deals with the board UARTs (i.e. serial devices). - -- ``clock``: - support for the clock tick - a regular time basis to the kernel. - -- ``timer``: - support of timer devices. - -- ``rtc`` or ``tod``: - support for the hardware real-time clock. - -- ``nvmem``: - support for non-volatile memory such as EEPROM or Flash. - -- ``network``: - the Ethernet driver. - -- ``shmsupp``: - support of shared memory driver MPCI layer in a multiprocessor system, - -- ``include``: - include files for this BSP. - -- ``gnatsupp``: - BSP specific support for the GNU Ada run-time. Each BSP that wishes to have - the possibility to map faults or exceptions into Ada language exceptions or - hardware interrupts into Ada interrupt tasks must provide this support. - -There may be other directories in the BSP tree and the name should be -indicative of the functionality of the code within that directory. - -The build order of the BSP is determined by the Makefile structure. This -structure is discussed in more detail in the :ref:`Makefiles` chapter. - -.. sidebar: - -This manual refers to the gen68340 BSP for numerous concrete examples. You -should have a copy of the gen68340 BSP available while reading this piece of -documentation. This BSP is located in the following directory: - -.. code-block:: c - - c/src/lib/libbsp/m68k/gen68340 - -Later in this document, the $BSP340_ROOT label will be used to refer to this -directory. |