libsigrok/HACKING

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HACKING
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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.


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
------------

 - 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_ASIX_SIGMA_ASIX_SIGMA_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.


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.


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.