Changeset 0184167 in rtems-docs


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Timestamp:
Dec 2, 2018, 8:44:29 AM (5 months ago)
Author:
Pritish Jain <pritishjain2001@…>
Branches:
master
Children:
e55248d
Parents:
65476b4
git-author:
Pritish Jain <pritishjain2001@…> (12/02/18 08:44:29)
git-committer:
Joel Sherrill <joel@…> (12/18/18 00:45:49)
Message:

coding-doxygen-bsp: Convert TBD to rest Format(GCI 2018)

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1 edited

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  • eng/coding-doxygen-bsp.rst

    r65476b4 r0184167  
    44.. COMMENT: RTEMS Foundation, The RTEMS Documentation Project
    55
    6 BSP Doxygen Recommentations
    7 ===========================
    8 
    9 TBD  - Convert the following to Rest and insert into this file
    10 TBD - https://devel.rtems.org/wiki/Developer/Coding/Doxygen_for_BSPs
     6
     7.. COMMENT:TBD  - Convert the following to Rest and insert into this file
     8.. COMMENT:TBD - https://devel.rtems.org/wiki/Developer/Coding/Doxygen_for_BSPs
     9
     10
     11Doxygen Recommendations for BSPs
     12==================================================
     13
     14RTEMS contains well over a hundred `Board Support Packages (BSPs) <wiki:TBR/Website/Board_Support_Packages>`_. , across over 20 different `CPU Architectures <wiki:TBR/UserManual/SupportedCPUs>`_. . What this means is that there is a lot of hardware dependent code that gets written, and that adding Doxygen to properly document it all can be a very complicated task.
     15
     16The goal of this document is to attempt to simplify this process a bit, and to get you started on adding Doxygen to the bsps/ directory in a way that is logical and has structure. Before we move on to detailing the process of actually adding Doxygen to BSPs, you will be greatly served by having at least a basic understanding of the purpose of a Board Support Package (it always helps to know a bit about what you're documenting), as well as of the existing structure of the bsps/ directory.
     17
     18Feel free to skip around and skim parts of this.
     19
     20BSP Basics
     21=================================================
     22
     23Embedded development is hard. Different CPUs have different instructions for doing the same thing, and different boards will have all sorts of different hardware that require unique drivers and interfaces. RTEMS handles this by having discrete packages, BSPs, to encapsulate code to accommodate for unique hardware. BSPs seek to implement the Hardware-Software interface. This, in a nutshell, is one of the `core purposes <wiki:Mission_Statement>`_. of RTEMS: To abstract (as much as is possible) away from the physical hardware and provide a standards compliant real-time environment for the embedded developer. If you think about it, the operating system on your normal computer serves a very similar purpose.
     24
     25Common Features Found In BSPs
     26=============================================
     27Although the actual implementation code will differ between BSPs, all BSPs will share some degree of common functionality. This is because that no matter what exact hardware you have, you need some basic features implemented in order to have a real time system you can develop on. Some of the most common shared features across most boards include:
     28
     29 *  **console**: is technically the serial driver for the BSP rather than just a console driver, it deals with the board UART (i.e. serial devices)
     30 *  **clock**: support for the clock tick - a regular time basis for the kernel
     31 *  **timer**: support of timer devices, used for timing tests
     32 *  **rtc** or **tod**: support for the hardware real time clock
     33 *  **network**: the Ethernet driver
     34 *  **shmsupp**: support of shared memory driver MPCI layer in a multiprocessor system
     35 *  **gnatsupp**: BSP specific support for the GNU Ada run-time
     36 *  **irq**: support for how the processor handles interrupts (probably the most common module shared by all boards)
     37 *  **tm27**: specific routines for the tm27 timing test
     38 *  **start** and **startup**: c and assembly used to initialize the board during startups/resets/reboots
     39
     40These are just some of the things you should be looking for when adding Doxygen to a BSP.
     41
     42Note that there is no guarantee a particular BSP will implement all of these features, or even some of them. These are just the most common ones to look for. RTEMS follows a standardized naming convention for the BSP sub directories, so you should be able to tell in most cases what has been implemented on the BSP level and what has not.
     43
     44Shared Features
     45====================================================
     46
     47Some of the RTEMS executive is hardware independent and can be abstracted so that the same piece of code can be shared across multiple CPU architectures, or across multiple boards on the same architecture. This is done so that chunks of software can be reused, as well as aiding in reducing the development and debugging time for implementing new BSPs. This greatly aids the developer, but as someone seeking to document this code, this can make your life a little bit harder. It is hard to tell by looking at the directory of a BSP which features have simply been left out and which features are being implemented by using shared code from either from the architecture (../shared) or the base bsps/ shared directory (../../shared). You may be looking at the BSP headers and notice that you have an irq.h, but no irq.c implementing it, or you might even be missing both. You know that the processor has interrupt support somehow, but where is it? The easiest way to figure this out is by looking at the Makefile.am for a BSP. We'll detail this process more in a bit.
     48
     49Rationale
     50=======================================================
     51
     52As someone adding documentation and not doing actual development work, you might think it is not necessary to know some of the in and outs of BSPs. In actuality, this information will prove to be very useful. Doxygen documentation works by grouping things and their components (i.e. functions and other definitions), and by having brief descriptions of what each group does. You can't know what to look for or know how to group it or know how to describe it without some basic knowledge of what a BSP is. For more information on any of the above or BSPs in general, check out the `BSP Development Guide <http://rtems.org/onlinedocs/doc-current/share/rtems/html/bsp_howto/index.html>`_. .
     53
     54The Structure of the bsps/ directory
     55===================================================
     56
     57All BSPs are found within the bsps/ directory, which is itself very well ordered. At the first level, we find a directory for each CPU architecture RTEMS supports, as well as a directory for code shared by all implementations.
     58
     59.. code block:: shell
     60$ cd bsps
     61$ ls
     62arm   bsp.am  lm32  m68k             mips   no_cpu         README  sparc
     63avr   h8300   m32c  Makefile.am      moxie  powerpc        sh      sparc64
     64bfin  i386    m32r  MERGE.PROCEDURE  nios2  preinstall.am  shared  v850
     65
     66
     67If we cd into a specific architecture, we see that a similar structure is employed. bsps/arm/ contains directories for each Board Support Package for boards with an ARM cpu, along with a folder for files and .h's shared by all BSPs of that architecture.
     68
     69.. code block:: shell
     70$ cd arm
     71$ ls
     72acinclude.m4  edb7312    gumstix   Makefile.am    realview-pbx-a9  stm32f4
     73configure.ac  gba        lm3s69xx  nds            rtl22xx          xilinx-zynq
     74csb336        gdbarmsim  lpc24xx   preinstall.am  shared
     75csb337        gp32       lpc32xx   raspberrypi    smdk2410
     76
     77
     78Finally, if we cd into a specific BSP, we see the files and .h's that compose the package for that particular board. You may recognize the directory names as some of the [common features] we outlined above, like '''irq''', '''clock''', '''console''', and '''startup'''. These directories contain implementations of these features.
     79
     80.. code block:: shell
     81$ cd raspberrypi
     82$ ls
     83bsp_specs  configure.ac  include  make         misc           README
     84clock      console       irq      Makefile.am  preinstall.am  startup
     85
     86
     87Another way to get an idea of the structure of bsps/ is to navigate to a directory and execute the "tree -f" command. This outputs a nice graphic that conveys some of the hierarchical properties of a particular directory.
     88
     89.. code block:: shell
     90$ pwd
     91~/rtems/bsps/arm/raspberrypi
     92$ tree -f
     93.
     94|-- ./bsp_specs
     95|-- ./clock
     96|   `-- ./clock/clockdrv.c
     97|-- ./configure.ac
     98|-- ./console
     99|   |-- ./console/console-config.c
     100|   `-- ./console/usart.c
     101|-- ./include
     102|   |-- ./include/bsp.h
     103|   |-- ./include/irq.h
     104|   |-- ./include/mmu.h
     105|   |-- ./include/raspberrypi.h
     106|   `-- ./include/usart.h
     107|-- ./irq
     108|   `-- ./irq/irq.c
     109|-- ./make
     110|   `-- ./make/custom
     111|       `-- ./make/custom/raspberrypi.cfg
     112|-- ./Makefile.am
     113|-- ./misc
     114|   `-- ./misc/timer.c
     115|-- ./preinstall.am
     116|-- ./README
     117`-- ./startup
     118    |-- ./startup/bspreset.c
     119    |-- ./startup/bspstart.c
     120    |-- ./startup/bspstarthooks.c
     121    |-- ./startup/linkcmds
     122    `-- ./startup/mm_config_table.c
     123
     124
     125
     126In short, BSPs will use the following directories:
     127 *  bsps/**shared**                        <- code used that is shared by all BSPs
     128 *  bsps/**CPU**/**shared**          <- code used shared by all BSPs of a particular CPU architecture
     129 *  bsps/**CPU**/**BSP**             <- code unique to this BSP
     130
     131As you can see, the bsps/ directory has a very logical and easy to understand structure to it. The documentation generated by Doxygen should attempt to match this structure as closely as possible. We want an overarching parent group to serve the same purpose as the bsps/ directory. In it, we want groups for each CPU architecture and a group for the shared files. We then want groups for each BSP. Breaking our documentation up into discrete groups like this will greatly simplify the process and make the documentation much easier to go through. By learning about the existing structure of the bsps/ directory, we get an idea of how we should structure the Doxygen groups we create. More on this in the next section.
     132
     133Doxygen
     134============================
     135Now that we have covered some of the preliminaries, we can move on to what you are actually reading this wiki page for: adding Doxygen to the bsps/ directory. Let's start with some Doxygen basics. Skip this if you are already comfortable with Doxygen.
     136
     137In addition to this, check out the page on `Doxygen Recommendations <wiki:Developer/Coding/Doxygen >`_. , which also contains a fair amount of information that will not be covered here.
     138
     139Doxygen Basics
     140=====================================================
     141
     142Doxygen is a documentation generator. It allows for documentation to be written right by the source code, greatly easing the pains of keeping documentation relevant and up to date. Doxygen has many commands, used for things like annotating functions with descriptions, parameter information, or return value information. You can reference other files or even other documentation.
     143
     144The core component of Doxygen (that we care about right now at least) is what's called a **group**, or **module**. These are used to add structure and associate groups of files that serve a similar purpose or implement the same thing.
     145
     146Doxygen Headers
     147=====================================
     148Doxygen is always found in a special Doxygen comment block, known as a **Doxygen header**. In RTEMS, this block comes in the form of a multiline comment with some included Doxygen commands, which are preceded by the '@' tag. Take a look at this Doxygen header that declares the arm_raspberrypi module, which houses the documentation in the BSP for the Raspberry Pi.
     149
     150.. code block:: shell
     151bsps/arm/raspberrypi/include/bsp.h:
     152
     153/**
     154 * @defgroup arm_raspberrypi Raspberry Pi Support
     155 *
     156 * @ingroup bsp_arm
     157 *
     158 * @brief Raspberry Pi support package
     159 *
     160 */
     161
     162
     163
     164You see a few commands here that we'll cover in the following sections. Briefly, the @defgroup command declares a new group, the @ingroup command nests this group as a submodule of some other group (in this case bsp_arm), and the @brief command provides a brief description of what this group is.
     165
     166 The @defgroup Command
     167==========================================
     168
     169The @defgroup command is used to declare new groups or modules. Think "define group". The syntax of this command is as follows:
     170
     171.. code block:: shell
     172@defgroup <group name> <group description>
     173
     174
     175The group name is the name used by Doxygen elsewhere to reference this group. The group description is what is displayed when the end user navigates to this module in the resulting documentation. The group description is a couple words formatted as how it would be in a table of contents. This part is what actually shows up in the documentation, when the user navigates to this group's module, this description will be the modules name.
     176
     177Groups should only be declared (@defgroup) in .h files. This is because Doxygen is used primarily to document interfaces, which are only found in .h files. Placing @defgroups in .h files is the only real restriction. Which .h file you place the group declaration in surprisingly doesn't matter. There is no information in the resulting documentation that indicates where the group was declared. You will see that we do have some rules for where you should place these declarations, but we also use this fact that it doesn't matter to our advantage, in order to standardize things.
     178
     179The @defgroup command is used only to define ''structure''. No actual documentation is generated as a result of its use. We must @ingroup things to the group we declare in order to create documentation. Even though it does not generate visible documentation, the @defgroup command is still very important. We use it in a way that seeks to emulate the structure of the bsps/ directory itself. We do this by creating a hierarchy of groups for each CPU architecture and each BSP.
     180
     181The @ingroup Command
     182=============================================
     183
     184The @ingroup command is used to add 'things' to already declared groups or modules. These 'things' can either be other groups, or files themselves. The syntax of the @ingroup command is as follows:
     185
     186.. code block:: shell
     187@ingroup <group name>
     188
     189
     190The group name is the actual name, not description, of the group you want to add yourself to. Remember that group name was the second argument passed to the @defgroup command.
     191
     192Using the @ingroup command is how we add ''meaning'' to the ''structure'' created by using @defgroup. @ingroup associates the file it is found in and all other Doxygen found within (function annotations, prototypes, etc) with the group we declared with the @defgroup command. We add related files and headers to the same groups to create a logical and cohesive body of documentation. If the end user wanted to read documentation about how the raspberry pi handles interrupts, all they would have to do would be to navigate to the raspberry pi's interrupt support module (which we created with a @defgroup command), and read the documentation contained within (which we added with @ingroup commands).
     193
     194@ingroup is found within all Doxygen headers, along with an @brief statement. There are two types of Doxygen headers, which we will go over after we see a description of the @brief command.
     195
     196 The @brief Command
     197=====================================================
     198
     199The @brief command is used to give either a)  a brief description in the form of an entry as you would see it in a table of contents (i.e. Capitalized, only a couple of words) or b) a brief topic sentence giving a basic idea of what the group does. The reason you have two uses for the brief command is that it is used differently in the two types of Doxygen headers, as we will see shortly. The syntax of the brief command is self evident, but included for the sake of completion:
     200
     201.. code block:: shell
     202@brief <Table of Contents entry '''or''' Topic Sentence>
     203
     204
     205The Two Types of Doxygen Headers
     206=================================================
     207
     208There are two types of Doxygen Headers. The first type is found at the beginning of a file, and contains an @file command. This type of header is used when @ingroup-ing the file into another doxygen group. The form of the @brief command in this case is a topic sentence, often very close to the file name or one of it's major functions. An example of this type of header, found in bsps/arm/raspberrypi/include/bsp.h is as follows:
     209
     210.. code block:: shell
     211Header type 1: used to add files to groups, always found at the beginning of a file
     212/**
     213 * @file
     214 *
     215 * @ingroup raspberrypi
     216 *
     217 * @brief Global BSP definitions.
     218 */
     219
     220/*
     221 * Copyright (c) 2013 Alan Cudmore
     222 *
     223...
     224
     225
     226Notice the form and placement of this type of header. It is always found at the beginning of a file, and is in its own multiline comment block, separated by one line white space from the copyright. If you look at the header itself, you see a @file, @ingroup, and @brief command. Consider the @file and the @ingroup together, what this says is that we are adding this file to the raspberrypi group. There is actually a single argument to the @file command, but Doxygen can infer it, so we leave it out. Any other Doxygen, function annotations, function prototypes, #defines, and other code included in the file will now be visible and documented when the end user navigates to the group you added it to in the resulting documentation.
     227
     228Now let's consider the second type of header. This type is syntactically very similar, but is used not to add files to groups, but to add groups to other groups. We use this type of header to define new groups and nest them within old groups. This is how we create hierarchy and structure within Doxygen. The following is found, again, in bsps/arm/raspberrypi/include/bsp.h:
     229
     230.. code block:: shell
     231Header type 2: Used to nest groups, found anywhere within a file
     232/**
     233 * @defgroup arm_raspberrypi Raspberry Pi Support
     234 *
     235 * @ingroup bsp_arm
     236 *
     237 * @brief Raspberry Pi Support Package
     238 */
     239
     240
     241It looks very similar to the first type of header, but notice that the @file command is replaced with the @defgroup command. You can think about it in the same way though. Here we are creating a new group, the arm_raspberry pi group, and nesting it within the bsp_arm group. The @brief in this case should be in the form of how you would see it in a table of contents. Words should be capitalized and there should be no period. This type of header can be found anywhere in a file, but it is typically found either in the middle before the file's main function, or at the tail end of a file. Recall that as we are using the @defgroup command and creating a new group in this header, the actual .h we place this in does not matter.
     242
     243The second type of header is the **structure** header, it's how we create new groups and implement hierarchy. The first type of header was the **meaning** header, it's how we added information to the groups we created.
     244
     245For more examples of Doxygen structure and syntax, refer to BSPs found within the arm architecture, the lpc32xx and raspberrypi BSPs are particularly well documented. A good way to quickly learn more is by tweaking some Doxygen in a file, then regenerating the html, and seeing what has changed.
     246
     247Generating Documentation
     248====================================================
     249
     250Doxygen is a documentation generator, and as such, we must generate the actual html documentation to see the results of our work. This is a very good way to check your work, and see if the resulting structure and organization was what you had intended. The best way to do this is to simply run the `do_doxygen script <https://github.com/joelsherrill/gci_tasks/blob/master/2015/doxygen_c_header_tasks/validate/do_doxygen>`_. . To use the script:
     251
     252Make sure Doxygen is installed. Also, the environment needs to have the root directory of RTEMS set in the variable `r` so that `$r` prints the path to RTEMS, and the script takes as argument a relative directory from there to generate the doxygen, for example to generate the doxygen for all of bsps/ you would do:
     253
     254.. code block:: shell
     255export r=~/rtems
     256./do_doxygen bsps
     257
     258
     259Doxygen in bsps/
     260==================================================
     261
     262Now that we've covered the basics of Doxygen, the basics of BSPs and the structure of the bsps/ directory, actually adding new Doxygen to bsps/ will be much easier than it was before. We will cover a set of rules and conventions that you should follow when adding Doxygen to this directory, and include some tips and tricks.
     263
     264 Group Naming Conventions
     265===================================================
     266
     267This is an easy one. These are in place in order for you to quickly identify some of the structure of the Doxygen groups and nested groups, without actually generating and looking at the documentation. The basic idea is this: when defining a new group (@defgroup), the form of the name should be the super group, or the name of the group you are nesting this group within, followed by an underscore, followed by the intended name of this new group. In command form:
     268
     269.. code block:: shell
     270          <----- This is your group name -------> <--usual description -->
     271@defgroup <super-group name>_<name of this group> <group description>
     272
     273
     274Some examples of this:
     275 *  **bsp_arm**: This is the group for the arm architecture. It is a member of the all inclusive bsp-kit group (more on this in structure conventions), so we prefix it with the "**bsp**" super group name. This is the group for the arm architecture, so the rest is just "'''arm'''"
     276 *  **arm_raspberrypi**: This is the group for the Raspberry Pi BSP. It is is an arm board, and as such, is nested within the bsp_arm group. We prefix the group name with an "**arm**" (notice we drop the bsp prefix of the arm group - we only care about the immediate super group), and the rest is a simple "'''raspberrypi'''", indicating this is the raspberrypi group, which is nested within the bsp_arm group.
     277 *  **raspberrypi_interrupt** This is the group for code handling interrupts on the Raspberry Pi platform. Because this code and the group that envelops it is Raspberry Pi dependent, we prefix our name with a "**raspberrypi**", indicating this group is nested within the raspberrypi group.= Structure Conventions =
     278
     279This covers where, when, and why you should place the second type of Doxygen header. Remember that our goal is to have the structure of the documentation to match the organization of the bsps/ directory as closely as possible. We accomplish this by creating groups for each cpu architecture, each BSP, and each shared directory. These groups are nested as appropriate in order to achieve a hierarchy similar to that of bsps/. The arm_raspberrypi group would be nested within the bsp_arm group, for example.
     280
     281 Where to place @defgroup
     282=====================================================
     283
     284Remember how I said it really doesn't matter where you place the @defgroup? Well, it does and it doesn't. It would be chaotic to place these anywhere, and almost impossible to tell when you have a @defgroup and when you don't, so we do have some rules in place to guide where you should place these.
     285
     286 @defgroups for CPU Architectures and Shared Directories
     287==============================================================================
     288
     289The standardized place for these is within a special doxygen.h file placed within the particular architectures shared directory. This doxygen.h file exists solely for this purpose, to provide a standard place to house the group definitions for CPU architectures and the shared directory for that architecture. This is done because there is no single file that all architectures share, so it would be impossible to declare a standardized location for architecture declarations without the creation of a new file. This also allows others to quickly determine if the group for a particular architecture has already been defined or not. Lets look at the doxygen.h for the arm architecture as an example, found at arm/shared/doxygen.h:
     290
     291.. code block:: shell
     292 /**
     293  *  @defgroup bsp_arm ARM
     294  *
     295  *  @ingroup bsp_kit
     296  *
     297  *  @brief ARM Board Support Packages
     298  */
     299
     300 /**
     301  *  @defgroup arm_shared ARM Shared Modules
     302  *
     303  *  @ingroup bsp_arm
     304  *
     305  *  @brief ARM Shared Modules
     306  */
     307
     308
     309
     310The doxygen.h contains only 2 Doxygen headers, both of which are of the second type. One header is used to create the groups for the arm architecture **bsp_arm**, nesting it as part of the bsp_kit group, and the other creates an **arm_shared** group to house the code that is shared across all BSPs of this architecture. Because these are the second type of Doxygen header, where we place them does not matter. This allows us to place them in a standard doxygen.h file, and the end user is non the wiser. Note that this .h file should never be included by a .c file, and that the only group declarations that should be placed here are the declarations for the CPU Architecture group and the shared group.
     311
     312There is also a doxygen.h file that exists at the root bsps/shared directory, to @defgroup the the parent **bsp_kit** group (the only group to not be nested within any other groups) and to @defgroup the **bsp_shared** group, to serve as the holder for the bsps/shared directory.
     313
     314If the architecture in which the BSP you are tasked with does not have one of these files already, you will need to copy the format of the file here, replacing the **arm** with whatever the CPU Architecture you are working with is. Name this file doxygen.h, and place it in the shared directory for that architecture.
     315
     316The only groups you should ever add to this CPU group would be groups for specific BSPs and a group for the shared directory.
     317
     318@defgroups for BSPs
     319=======================================
     320
     321These are much easier than placing @defgroups for CPU Architectures. The overwhelming majority of the time, the @defgroup for a BSP is found within the bsp.h file found at '''''bsp'''''/include/bsp.h. It is usually placed midway through or towards the end of the file. In the event that your board lacks a bsp.h file, include this group declaration within the most standard or commonly included header for that BSP.
     322
     323The group for a BSP should **always** be nested within the group for the CPU architecture it uses. This means that the Doxygen header for defining a BSP group should always look something like this:
     324
     325.. code block:: shell
     326 /**
     327  *  @defgroup *architecture*_*BSP* *name*
     328  *
     329  *  @ingroup bsp_*architecture*
     330  *
     331  *  @brief *BSP* Support Package
     332  */
     333
     334
     335 @defgroups for Everything Else
     336======================================================
     337
     338Never be afraid to add more structure! Once the basic CPU and BSP group hierarchy is established, what we're left with is all the sub directories and implementation code. Whether working within a shared directory for a CPU architecture, or within a BSP directory, you should always be looking for associations you can make to group files together by. Your goal should be to avoid @ingroup-ing files directly to the cpu_shared group and the cpu_bsp group as much as possible, you want to find more groups you can nest within these groups, and then @ingroup files to those groups. Here are some things to look for:
     339
     340==== Look Common Features Implemented
     341===================================================
     342
     343Remember that list of common features outlined in the BSP Basics section? Find the .h's that are responsible for providing the interface for these features, and @defgroup a group to @ingroup the files responsible for implementing this feature.
     344
     345RTEMS has a naming convention for its BSP sub directories, so it should be a really quick and easy process to determine what features are there and what is missing.
     346
     347Examples of this are found within the **arm_raspberrypi** group, which contains nested subgroups like **raspberry_interrupt** to group files responsible for handling interrupts, **raspberrypi_usart** to group files responsible for implementing USART support, and many other subgroups.
     348
     349==== Check out the Makefile
     350===============================================
     351
     352When working within a BSP, take a look at the Makefile.am. Often times, you will find that the original developer of the code has outlined the groups nicely for you already, with comments and titles before including source files to be built. Also, this is often the only way to tell which features a BSP simply does not implement, and which features a BSP borrows from either the architecture's shared group, or the bsps/ shared group.
     353
     354==== Start with a .h, and look for files that include it
     355=============================================================
     356
     357You should end up with a @defgroup for ''most'' .h files. Some .h files are related and will not have independent groups, but most provide interfaces for different features and should have their own group defined. Declare a group for the header, then use cscope to find the files that include this header, and try to determine where the implementation code for prototypes are found. These are the files you should @ingroup.
     358
     359==== Files with similar names
     360===============================================
     361
     362If you see that a few files have similar names, like they are all prefixed with the same characters, then these files should most likely be part of the same group.
     363
     364Remember, your goal is to @defgroup as much as you can. The only files you should be @ingroup-ing directly to the BSP group or the shared group are files that don't cleanly fit into any other group.
     365
     366Where to place @ingroup
     367=============================================
     368
     369The @ingroups you add should make sense.
     370
     371 * If you are working within an architecture's shared directory, @ingroup should be adding things either to the *architecture*_shared group, or some sub group of it.
     372 * If you are working within a BSP directory, @ingroup should be adding things to either the *architecture_*bsp* group, or some sub group of it.
     373
     374 @ingroup in the first type of Doxygen Header
     375========================================================
     376
     377Remember that in the first type of Doxygen header, we are adding files to groups. This type of header should always be at the top of the file. You should be adding files that are associated in some way to the same groups. That is to say, if three different .h files provide an interface allowing interrupt support, they should be a part of the same group. Some good ways to associate files were outlined above.
     378
     379 @ingroup in the second type of Doxygen Header ===
     380==================================================================
     381Here we are using the @ingroup command to add groups to other groups, creating a hierarchy. The goal for bsps/ is to have one single group that holds all other groups. This root group is the **bsp_kit** group. All groups should be added either directly to this group (if you are creating an architecture group) or added to one of its sub groups.
     382
     383When nesting groups, try to match the structure of bsps/ as closely as possible. For example, if a group is defined to associate all files that provide for a real time clock for the raspberrypi, nest it within the arm_raspberrypi group.
     384
     385@ingroup for shared code
     386================================================
     387
     388This is tricky. You may end up in a situation where your BSP uses code found in either the architecture shared directory, or the bsps/shared directory. Even though this code is logically associated with the BSP, as stated above: all files in the shared directory should be added to either the *architecture*_shared group, or some subgroup of it ''not'' the BSP group. You could make a note under the @brief line in the header (which shows up in the resulting documentation) that a particular BSP uses this code.
     389
     390When working with shared code, you should be careful and add notes to @brief to indicate that it is a shared code or interface. Prefixing things with "Generic" is a good idea here. You will still be able to form groups and associate things when working on the shared level, but sometimes you will find that you have the interface (.h) to @defgroup, but not many files to add to the group as it may be hardware dependent. This is okay.
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