[libsigrok.git] / HACKING

-------------------------------------------------------------------------------
HACKING
-------------------------------------------------------------------------------

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

This project is programmed using the Linux kernel coding style:

  https://www.kernel.org/doc/html/latest/process/coding-style.html

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


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

 - In order to contribute you should ideally clone the git repository and
   let us know (preferably via IRC, or via the mailing list) from where to
   pull/review your changes. You can use github.com, or any other public git
   hosting site.

 - Alternatively, patches can 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


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 src/hardware/tondaj-sl-814 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:

 - Makefile.am: Add to src_libdrivers_la_SOURCES under the HW_TONDAJ_SL_814
   condition.
 - configure.ac: Add an SR_DRIVER() call.
 - src/drivers.c: Add a tondaj_sl_814_driver_info entry in two places.
 - src/hardware/tondaj-sl-814/ directory: Add 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_*malloc() / g_*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_*malloc()/g_*malloc0() was used, use g_free() to free the
   memory. Otherwise use standard free(). Never use the wrong function!

 - We assume that "small" memory allocations (< 1MB) will always succeed.
   Thus, it's fine to use g_malloc() or g_malloc0() for allocations of
   simple/small structs and such (instead of using g_try_malloc()), and
   there's no need to check the return value.

   Do use g_try_malloc() or g_try_malloc0() for large (>= 1MB) allocations
   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.
   Example: 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
-------

 - Use the @ notation for all Doxygen comments (e.g. @param, not \param).

 - Do not use the @brief tag, it's unnecessary as we use JAVADOC_AUTOBRIEF.

 - Generally use the following item order in Doxygen comments:
    - Brief function description (1 line), followed by an empty line.
    - Optionally, a longer function description (and another empty line).
    - The list of parameter descriptions (@param).
    - The return value description (@return or @retval).
    - An optional @since tag (only for public SR_API functions).
    - An optional @private tag (for private SR_PRIV functions).

 - In @param lines, the name of the parameter is followed by a space and
   then a sentence describing the parameter (starts with a capital letter,
   ends with a full stop).

 - 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. Functions in non-public files that
   are explicitly excluded in Doxyfile don't need to be marked either.
   Don't use @internal, always use @private instead.

 - 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.

 - Examples:

/**
 * Tell a hardware driver to scan for devices.
 *
 * In addition to the detection, the devices that are found are also
 * initialized automatically. On some devices, this involves a firmware upload,
 * or other such measures.
 *
 * The order in which the system is scanned for devices is not specified. The
 * caller should not assume or rely on any specific order.
 *
 * Before calling sr_driver_scan(), the user must have previously initialized
 * the driver by calling sr_driver_init().
 *
 * @param[in] driver The driver that should scan. Must be a pointer to one of
 *                   the entries returned by sr_driver_list(). Must not be NULL.
 * @param[in] options List of 'struct sr_hwopt' options to pass to the driver's
 *                    scanner. Can be NULL/empty.
 *
 * @return A GSList * of 'struct sr_dev_inst', or NULL if no devices were
 *         found (or errors were encountered). This list must be freed by the
 *         caller using g_slist_free(), but without freeing the data pointed
 *         to in the list.
 *
 * @since 0.2.0
 */

/**
 * Query value of a configuration key at the given driver or device instance.
 *
 * @param[in] driver The sr_dev_driver struct to query. Must not be NULL.
 * @param[in] sdi (optional) If the key is specific to a device, this must
 *            contain a pointer to the struct sr_dev_inst to be checked.
 *            Otherwise it must be NULL. If sdi is != NULL, sdi->priv must
 *            also be != NULL.
 * @param[in,out] data Pointer to a GVariant where the value will be stored.
 *             Must not be NULL. The caller is given ownership of the GVariant
 *             and must thus decrease the refcount after use. However if
 *             this function returns an error code, the field should be
 *             considered unused, and should not be unreferenced.
 *
 * @retval SR_OK Success.
 * @retval SR_ERR Error.
 * @retval SR_ERR_ARG The driver doesn't know that key, but this is not to be
 *         interpreted as an error by the caller; merely as an indication
 *         that it's not applicable.
 *
 * @since 0.3.0
 * @private
 */


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.
Commit	Line	Data
	1	-------------------------------------------------------------------------------
	2	HACKING
	3	-------------------------------------------------------------------------------
	4
	5	Coding style
	6	------------
	7
	8	This project is programmed using the Linux kernel coding style:
	9
	10	https://www.kernel.org/doc/html/latest/process/coding-style.html
	11
	12	Please use the same style for any code contributions, thanks!
	13
	14
	15	Contributions
	16	-------------
	17
	18	- In order to contribute you should ideally clone the git repository and
	19	let us know (preferably via IRC, or via the mailing list) from where to
	20	pull/review your changes. You can use github.com, or any other public git
	21	hosting site.
	22
	23	- Alternatively, patches can be sent to the development mailinglist at
	24	sigrok-devel@lists.sourceforge.net (please subscribe to the list first).
	25
	26	https://lists.sourceforge.net/lists/listinfo/sigrok-devel
	27
	28
	29	Adding a new hardware driver
	30	----------------------------
	31
	32	The simple, scripted way (recommended):
	33	---------------------------------------
	34
	35	Use the 'new-driver' script from the sigrok-util repo:
	36
	37	$ git clone git://sigrok.org/sigrok-util
	38	$ cd sigrok-util/source
	39	$ ./new-driver "Tondaj SL-814"
	40
	41	The example above generates a patch file against the current libsigrok
	42	development git tree which adds a simple "stub" driver for your device
	43	(the Tondaj SL-814 sound level meter in this case).
	44
	45	You can apply it like this:
	46
	47	$ cd libsigrok
	48	$ git am 0001-tondaj-sl-814-Initial-driver-skeleton.patch
	49
	50	You can now edit the files in src/hardware/tondaj-sl-814 as needed
	51	and implement your driver based on the skeleton files there. That means your
	52	patch submission later will consist of at least two patches: the initial one
	53	adding the skeleton driver, and one or more additional patches that actually
	54	implement the respective driver code.
	55
	56
	57	The manual way:
	58	---------------
	59
	60	This is a rough overview of what you need to do in order to add a new driver
	61	(using the Tondaj SL-814 device as example). It's basically what the
	62	'new-driver' script (see above) does for you:
	63
	64	- Makefile.am: Add to src_libdrivers_la_SOURCES under the HW_TONDAJ_SL_814
	65	condition.
	66	- configure.ac: Add an SR_DRIVER() call.
	67	- src/drivers.c: Add a tondaj_sl_814_driver_info entry in two places.
	68	- src/hardware/tondaj-sl-814/ directory: Add api.c, protocol.c, protocol.h.
	69
	70	See existing drivers or the 'new-driver' output for the details.
	71
	72
	73	Random notes
	74	------------
	75
	76	- Don't do variable declarations in compound statements, only at the
	77	beginning of a function.
	78
	79	- Generally avoid assigning values to variables at declaration time,
	80	especially so for complex and/or run-time dependent values.
	81
	82	- Consistently use g_malloc() / g_malloc0(). Do not use standard
	83	malloc()/calloc() if it can be avoided (sometimes other libs such
	84	as libftdi can return malloc()'d memory, for example).
	85
	86	- Always properly match allocations with the proper *free() functions. If
	87	glib's g_malloc()/g_malloc0() was used, use g_free() to free the
	88	memory. Otherwise use standard free(). Never use the wrong function!
	89
	90	- We assume that "small" memory allocations (< 1MB) will always succeed.
	91	Thus, it's fine to use g_malloc() or g_malloc0() for allocations of
	92	simple/small structs and such (instead of using g_try_malloc()), and
	93	there's no need to check the return value.
	94
	95	Do use g_try_malloc() or g_try_malloc0() for large (>= 1MB) allocations
	96	and check the return value.
	97
	98	- You should never print any messages (neither to stdout nor stderr nor
	99	elsewhere) "manually" via e.g. printf() or g_log() or similar functions.
	100	Only sr_err()/sr_warn()/sr_info()/sr_dbg()/sr_spew() should be used.
	101
	102	- Use glib's gboolean / TRUE / FALSE for boolean types consistently.
	103	Do not use <stdbool.h> and its true / false, and do not invent private
	104	definitions for this either.
	105
	106	- Consistently use the same naming convention for #include guards in headers:
	107	<PROJECTNAME>_<PATH_TO_FILE>_<FILE>
	108	This ensures that all #include guards are always unique and consistent.
	109	Example: LIBSIGROK_HARDWARE_MIC_985XX_PROTOCOL_H
	110
	111	- Consistently use the same naming convention for API functions:
	112	<libprefix>_<groupname>_<action>().
	113
	114	Examples:
	115	sr_log_loglevel_set(), sr_log_loglevel_get(), sr_log_handler_set(),
	116	sr_log_handler_set_default(), and so on.
	117	Or:
	118	sr_session_new(), sr_session_destroy(), sr_session_load(), and so on.
	119
	120	Getter/setter function names should usually end with "_get" or "_set".
	121	Functions creating new "objects" should end with "_new".
	122	Functions destroying "objects" should end with "_destroy".
	123	Functions adding or removing items (e.g. from lists) should end with
	124	either "_add" or "_remove".
	125	Functions operating on all items from a list (not on only one of them),
	126	should end with "_all", e.g. "_remove_all", "_get_all", and so on.
	127	Use "_remove_all" in favor of "_clear" for consistency.
	128
	129	- All enums should generally use an explicit start number of 10000.
	130	If there are multiple "categories" in the enum entries, each category
	131	should be 10000 entries apart from the next one. The start of categories
	132	are thus 10000, 20000, 30000, and so on.
	133
	134	Adding items to an enum MUST always append to a "category", never add
	135	items in the middle of a category. The order of items MUST NOT be changed.
	136	Any of the above would break the ABI.
	137
	138	The enum item 0 is special and is used as terminator in some lists, thus
	139	enums should not use this for "valid" entries (and start at 10000 instead).
	140
	141
	142	Doxygen
	143	-------
	144
	145	- Use the @ notation for all Doxygen comments (e.g. @param, not \param).
	146
	147	- Do not use the @brief tag, it's unnecessary as we use JAVADOC_AUTOBRIEF.
	148
	149	- Generally use the following item order in Doxygen comments:
	150	- Brief function description (1 line), followed by an empty line.
	151	- Optionally, a longer function description (and another empty line).
	152	- The list of parameter descriptions (@param).
	153	- The return value description (@return or @retval).
	154	- An optional @since tag (only for public SR_API functions).
	155	- An optional @private tag (for private SR_PRIV functions).
	156
	157	- In @param lines, the name of the parameter is followed by a space and
	158	then a sentence describing the parameter (starts with a capital letter,
	159	ends with a full stop).
	160
	161	- In Doxygen comments, put an empty line between the block of @param lines
	162	and the final @return line. The @param lines themselves (if there is more
	163	than one) are not separated by empty lines.
	164
	165	- Mark private functions (SR_PRIV) with /** @private */, so that Doxygen
	166	doesn't include them in the output. Functions that are "static" anyway
	167	don't need to be marked like this. Functions in non-public files that
	168	are explicitly excluded in Doxyfile don't need to be marked either.
	169	Don't use @internal, always use @private instead.
	170
	171	- Mark private variables/#defines with /** @cond PRIVATE */ and
	172	/** @endcond */, so that Doxygen doesn't include them in the output.
	173	Variables that are "static" don't need to be marked like this.
	174
	175	- Mark all public API functions (SR_API) with a @since tag which indicates
	176	in which release the respective function was added (e.g. "@since 0.1.0").
	177
	178	If the function has existed before, but its API changed later, the @since
	179	tag should mention only the release when the API last changed.
	180
	181	Example: The sr_foo() call was added in 0.1.0, but the API changed in
	182	the later 0.2.0 release. The docs should read "@since 0.2.0" in that case.
	183
	184	Non-public functions (static ones, and those marked SR_PRIV) don't need
	185	to have @since markers.
	186
	187	The @since tag should be the last one, i.e. it should come after @param,
	188	@return, @see, and so on.
	189
	190	- Examples:
	191
	192	/**
	193	* Tell a hardware driver to scan for devices.
	194	*
	195	* In addition to the detection, the devices that are found are also
	196	* initialized automatically. On some devices, this involves a firmware upload,
	197	* or other such measures.
	198	*
	199	* The order in which the system is scanned for devices is not specified. The
	200	* caller should not assume or rely on any specific order.
	201	*
	202	* Before calling sr_driver_scan(), the user must have previously initialized
	203	* the driver by calling sr_driver_init().
	204	*
	205	* @param[in] driver The driver that should scan. Must be a pointer to one of
	206	* the entries returned by sr_driver_list(). Must not be NULL.
	207	* @param[in] options List of 'struct sr_hwopt' options to pass to the driver's
	208	* scanner. Can be NULL/empty.
	209	*
	210	* @return A GSList * of 'struct sr_dev_inst', or NULL if no devices were
	211	* found (or errors were encountered). This list must be freed by the
	212	* caller using g_slist_free(), but without freeing the data pointed
	213	* to in the list.
	214	*
	215	* @since 0.2.0
	216	*/
	217
	218	/**
	219	* Query value of a configuration key at the given driver or device instance.
	220	*
	221	* @param[in] driver The sr_dev_driver struct to query. Must not be NULL.
	222	* @param[in] sdi (optional) If the key is specific to a device, this must
	223	* contain a pointer to the struct sr_dev_inst to be checked.
	224	* Otherwise it must be NULL. If sdi is != NULL, sdi->priv must
	225	* also be != NULL.
	226	* @param[in,out] data Pointer to a GVariant where the value will be stored.
	227	* Must not be NULL. The caller is given ownership of the GVariant
	228	* and must thus decrease the refcount after use. However if
	229	* this function returns an error code, the field should be
	230	* considered unused, and should not be unreferenced.
	231	*
	232	* @retval SR_OK Success.
	233	* @retval SR_ERR Error.
	234	* @retval SR_ERR_ARG The driver doesn't know that key, but this is not to be
	235	* interpreted as an error by the caller; merely as an indication
	236	* that it's not applicable.
	237	*
	238	* @since 0.3.0
	239	* @private
	240	*/
	241
	242
	243	Testsuite
	244	---------
	245
	246	You can run the libsigrok testsuite using:
	247
	248	$ make check
	249
	250
	251	Release engineering
	252	-------------------
	253
	254	See
	255
	256	http://sigrok.org/wiki/Developers/Release_process
	257
	258	for a list of items that need to be done when releasing a new tarball.
	259