File: HACKING

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libsigrok 0.3.0-1
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-------------------------------------------------------------------------------
HACKING
-------------------------------------------------------------------------------

Coding style
------------

This project is programmed using the Linux kernel coding style, see
http://lxr.linux.no/linux/Documentation/CodingStyle for details.

Please use the same style for any code contributions, thanks!


Contributions
-------------

 - Patches should be sent to the development mailinglist at
   sigrok-devel@lists.sourceforge.net (please subscribe to the list first).

   https://lists.sourceforge.net/lists/listinfo/sigrok-devel

 - Alternatively, you can also clone the git repository and let us know
   from where to pull/review your changes. You can use gitorious.org,
   github.com, or any other public git hosting site.


Adding a new hardware driver
----------------------------

The simple, scripted way (recommended):
---------------------------------------

Use the 'new-driver' script from the sigrok-util repo:

 $ git clone git://sigrok.org/sigrok-util
 $ cd sigrok-util/source
 $ ./new-driver "Tondaj SL-814"

The example above generates a patch file against the current libsigrok
development git tree which adds a simple "stub" driver for your device
(the Tondaj SL-814 sound level meter in this case).

You can apply it like this:

 $ cd libsigrok
 $ git am 0001-tondaj-sl-814-Initial-driver-skeleton.patch

You can now edit the files in the hardware/tondaj-sl-814 directory as needed
and implement your driver based on the skeleton files there. That means your
patch submission later will consist of at least two patches: the initial one
adding the skeleton driver, and one or more additional patches that actually
implement the respective driver code.


The manual way:
---------------

This is a rough overview of what you need to do in order to add a new driver
(using the Tondaj SL-814 device as example). It's basically what the
'new-driver' script (see above) does for you:

 - configure.ac:
   - Add an --enable-tondaj-sl-814 option.
   - Add "hardware/tondaj-sl-814/Makefile" to the AC_CONFIG_FILES list.
   - Add and entry for the device in the "Enabled hardware drivers" list
     at the bottom of the file.
 - hardware/Makefile.am: Add "tondaj-sl-814" to the SUBDIRS variable.
 - hwdriver.c: Add a tondaj_sl_814_driver_info entry in two places.
 - hardware/tondaj-sl-814/ directory: Add the following files:
   Makefile.am, api.c, protocol.c, protocol.h

See existing drivers or the 'new-driver' output for the details.


Random notes
------------

 - Don't do variable declarations in compound statements, only at the
   beginning of a function.

 - Generally avoid assigning values to variables at declaration time,
   especially so for complex and/or run-time dependent values.

 - Consistently use g_try_malloc() / g_try_malloc0(). Do not use standard
   malloc()/calloc() if it can be avoided (sometimes other libs such
   as libftdi can return malloc()'d memory, for example).

 - Always properly match allocations with the proper *free() functions. If
   glib's g_try_malloc()/g_try_malloc0() was used, use g_free() to free the
   memory. Otherwise use standard free(). Never use the wrong function!

 - Never use g_malloc() or g_malloc0(). These functions do not return NULL
   if not enough memory is available but rather lead to an exit() or segfault
   instead. This behaviour is not acceptable for libraries.
   Use g_try_malloc()/g_try_malloc0() instead and check the return value.

 - You should never print any messages (neither to stdout nor stderr nor
   elsewhere) "manually" via e.g. printf() or g_log() or similar functions.
   Only sr_err()/sr_warn()/sr_info()/sr_dbg()/sr_spew() should be used.

 - Use glib's gboolean / TRUE / FALSE for boolean types consistently.
   Do not use <stdbool.h> and its true / false, and do not invent private
   definitions for this either.

 - Consistently use the same naming convention for #include guards in headers:
   <PROJECTNAME>_<PATH_TO_FILE>_<FILE>
   This ensures that all #include guards are always unique and consistent.
   Examples: LIBSIGROK_LIBSIGROK_H, LIBSIGROK_HARDWARE_MIC_985XX_PROTOCOL_H

 - Consistently use the same naming convention for API functions:
   <libprefix>_<groupname>_<action>().

   Examples:
     sr_log_loglevel_set(), sr_log_loglevel_get(), sr_log_handler_set(),
     sr_log_handler_set_default(), and so on.
   Or:
     sr_session_new(), sr_session_destroy(), sr_session_load(), and so on.

   Getter/setter function names should usually end with "_get" or "_set".
   Functions creating new "objects" should end with "_new".
   Functions destroying "objects" should end with "_destroy".
   Functions adding or removing items (e.g. from lists) should end with
   either "_add" or "_remove".
   Functions operating on all items from a list (not on only one of them),
   should end with "_all", e.g. "_remove_all", "_get_all", and so on.
   Use "_remove_all" in favor of "_clear" for consistency.

 - All enums should generally use an explicit start number of 10000.
   If there are multiple "categories" in the enum entries, each category
   should be 10000 entries apart from the next one. The start of categories
   are thus 10000, 20000, 30000, and so on.

   Adding items to an enum MUST always append to a "category", never add
   items in the middle of a category. The order of items MUST NOT be changed.
   Any of the above would break the ABI.

   The enum item 0 is special and is used as terminator in some lists, thus
   enums should not use this for "valid" entries (and start at 10000 instead).


Doxygen
-------

 - In Doxygen comments, put an empty line between the block of @param lines
   and the final @return line. The @param lines themselves (if there is more
   than one) are not separated by empty lines.

 - Mark private functions (SR_PRIV) with /** @private */, so that Doxygen
   doesn't include them in the output. Functions that are "static" anyway
   don't need to be marked like this.

 - Mark private variables/#defines with /** @cond PRIVATE */ and
   /** @endcond */, so that Doxygen doesn't include them in the output.
   Variables that are "static" don't need to be marked like this.

 - Mark all public API functions (SR_API) with a @since tag which indicates
   in which release the respective function was added (e.g. "@since 0.1.0").

   If the function has existed before, but its API changed later, the @since
   tag should mention only the release when the API last changed.

   Example: The sr_foo() call was added in 0.1.0, but the API changed in
   the later 0.2.0 release. The docs should read "@since 0.2.0" in that case.

   Non-public functions (static ones, and those marked SR_PRIV) don't need
   to have @since markers.

   The @since tag should be the last one, i.e. it should come after @param,
   @return, @see, and so on.


Testsuite
---------

You can run the libsigrok testsuite using:

 $ make check


Release engineering
-------------------

See

 http://sigrok.org/wiki/Developers/Release_process

for a list of items that need to be done when releasing a new tarball.