Rename all manuals with an _ to have a -. It helps released naming of files.

1 files changed, 229 insertions, 0 deletions

diff --git a/bsp-howto/target_dependant_files.rst b/bsp-howto/target_dependant_files.rst
new file mode 100644
index 0000000..ecc9b3a
--- /dev/null
+++ b/bsp-howto/target_dependant_files.rst
@@ -0,0 +1,229 @@
+.. 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.