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diff --git a/bsp_howto/target_dependant_files.rst b/bsp_howto/target_dependant_files.rst index 31c3d1a..691e706 100644 --- a/bsp_howto/target_dependant_files.rst +++ b/bsp_howto/target_dependant_files.rst @@ -1,14 +1,18 @@ .. 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. +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 @@ -19,70 +23,68 @@ into one of the following categories. 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. +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. +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. +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. +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. +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: +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? @@ -90,46 +92,47 @@ a particular target board, the following questions should be asked: - 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. +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. If -you need help in making these modifications to RTEMS, please -consider using one of the RTEMS Service Providers. The current -list of these is at http://www.rtems.org/support.html. +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: +The CPU dependent files in the RTEMS executive source code are found in the +following directory: + .. code:: c - cpukit/score/cpu/*CPU* + cpukit/score/cpu/<CPU> -where *CPU* is replaced with the CPU family name. +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. +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 =========================== @@ -142,93 +145,85 @@ This class of code may be found in the following directory: .. code:: c - c/src/lib/libcpu/*CPU* + c/src/lib/libcpu/<CPU> CPU model dependent support code is found in the following directory: .. code:: c - c/src/lib/libcpu/*CPU*/*CPU_MODEL* + 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. +<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 (m68k, powerpc, 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: +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:: c c/src/lib/libbsp/shared - c/src/lib/libbsp/*CPU*/shared - c/src/lib/libbsp/*CPU*/*BSP* + 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. +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). +- ``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*: +- ``clock``: support for the clock tick - a regular time basis to the kernel. -- *timer*: +- ``timer``: support of timer devices. -- *rtc* or ``tod``: +- ``rtc`` or ``tod``: support for the hardware real-time clock. -- *nvmem*: +- ``nvmem``: support for non-volatile memory such as EEPROM or Flash. -- *network*: +- ``network``: the Ethernet driver. -- *shmsupp*: +- ``shmsupp``: support of shared memory driver MPCI layer in a multiprocessor system, -- *include*: +- ``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. +- ``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. +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 `Makefiles`_ -chapter. +The build order of the BSP is determined by the Makefile structure. This +structure is discussed in more detail in the `Makefiles`_ chapter. -*NOTE:* 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:: c - - c/src/lib/libbsp/m68k/gen68340 - -Later in this document, the $BSP340_ROOT label will be used -to refer to this directory. - -.. COMMENT: COPYRIGHT (c) 1988-2008. +.. sidebar: -.. COMMENT: On-Line Applications Research Corporation (OAR). + 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: -.. COMMENT: All rights reserved. +.. code:: c + c/src/lib/libbsp/m68k/gen68340 +Later in this document, the $BSP340_ROOT label will be used to refer to this +directory. |