path: root/HACKING

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HACKING
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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!

The Python decoders should follow the usual Python conventions and use
Python idioms as far as it makes sense. The coding style should mostly follow
the Python PEP-8, which includes the convention of 4 spaces for indentation:

  http://www.python.org/dev/peps/pep-0008/

Exceptions:

 - All strings should use single quotes ('foo' instead of "foo").

 - No double-newlines between methods (or anywhere else).


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


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 srd_err()/srd_warn()/srd_info()/srd_dbg()/srd_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: LIBSIGROKDECODE_LIBSIGROKDECODE_INTERNAL_H

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

   Examples:
     srd_log_loglevel_set(), srd_log_loglevel_get(), srd_log_handler_set(),
     srd_log_handler_set_default(), 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 (SRD_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 (SRD_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 srd_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 SRD_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.


Protocol decoder guidelines
---------------------------

 - The 'desc' metadata field for a protocol decoder, which contains a
   short, one-line description of the protocol/bus, should be at most 55
   characters long, and end with a full stop. This short description can be
   displayed on the command-line using "sigrok-cli -V -l 3", or in various
   different places in GUIs.

 - Longer, multi-line descriptions should be placed in the protocol
   decoder's __init__.py file as docstring. It can be viewed (for a specific
   protocol decoder, e.g., UART) via "sigrok-cli -P uart --show", or in various
   other places in GUIs.

 - Input IDs, output IDs, tags, channel IDs, option IDs, annotation class IDs,
   annotation row IDs, and binary class IDs each must be unique.

 - Annotation class IDs must not overlap with annotation row IDs.
   For example, you cannot have an annotation row named "foo" if you already
   have an annotation class named "foo". This avoids confusion for users
   and simplifies e.g. command-line usage of decoders.

 - Annotation class IDs should generally be singular, annotation row IDs
   should generally be plural. Example: UART annotation classes could be
   named "stop-bit" or "parity-bit" (singular), the annotation row containing
   these annotation classes could be named "bits" (plural).

 - Generally use strings for states (of the PD state machine), not integers.
   This avoids having to keep a list of state definitions at the top of file.
   The performance overhead for this is negligible in practice.

   Recommended:
     self.state = 'IDLE'
     self.state = 'GET STOP BIT'
   Not recommended:
     self.state = IDLE
     self.state = GET_STOP_BIT
     (where IDLE = 0 and GET_STOP_BIT = 1, for example)

 - Generally use strings for commands/IDs in generated protocol packets.
   This avoids having to know magic numbers of the PD in higher-level PDs.
   The performance overhead for this is negligible in practice.

   Recommended:
     self.put(x, y, p, ['STOPBIT', 0, 0])
     self.put(x, y, p, ['ADDRESS READ', 0x51])
   Not recommended:
     self.put(x, y, p, [STOPBIT, 0, 0])
     self.put(x, y, p, [ADDRESS_READ, 0x51])
     (with STOPBIT = 3 and ADDRESS_READ = 7, for example)

 - Use ALL-CAPS names for PD states and protocol packet commands/ID.
   Words should be separated by spaces (not underscores or the like).

   Recommended:
     'FIND ADDRESS', 'GET TEMPERATURE', 'START'
   Not recommended:
     'FIND_ADDRESS', 'Get Temperature', 'start'

 - Protocol decoder tags:

   - Every decoder must have a "tags" list (>= 1 items, alphabetically sorted).

   - All tag names start with a capital letter. Subsequent words of the name
     are not capitalized, e.g. "Retro computing", "Debug/trace".

   - All tag names should use singular form ("Sensor", not "Sensors").

   Common tags:

   - Analog/digital: Decoders related A/D conversion, e.g. ADCs and DACs.
   - Audio: Decoders related to audio protocols, e.g. I²S, S/PDIF.
   - Automotive: Decoders related to automotive protocols, e.g. CAN, FlexRay.
   - Clock/timing: Decoders related to time keeping, timing, and clocks/RTCs.
   - Debug/trace: Decoders related to microcontroller/CPU debugging, tracing,
     programming/flashing protocols, e.g. SWD, JTAG, AVR ISP, ARM ETMv3.
   - Display: Decoders related to display technologies, e.g. DVI, HDMI,
     TFT, OLED, LCD, HD44780, EDID, and various LED protocols.
   - Embedded/industrial: Decoders related to protocols used in embedded
     systems, industrial systems, or automation (e.g. SPI, Modbus, Profibus).
   - Encoding: Decoders related to generic encoding / line coding systems,
     e.g. Manchester, Miller, Gray code, OOK, and similar.
   - IC: Decoders for specific (families of) ICs (i.e. not IC-independent,
     generic protocols like UART, SPI, CAN, or USB).
   - IR: Decoders related to infrared (e.g. remote control) protocols.
   - Lighting: Decoders related to lighting technologies, e.g. DALI, DMX512.
   - Memory: Decoders related to memories (e.g. NOR/NAND flash, EEPROM,
     SDRAM, SRAM, various other volatile or non-volatile memories).
   - Networking: Decoders related to (wired) networking technologies.
   - PC: Decoders related to protocols used in personal computers (desktop,
     workstation, laptop, server). This is not meant to be restricted to
     "IBM PC" or "x86/Intel", Apple/Commodore/Atari/SPARC etc. are fine too.
   - RFID: Decoders related to RFID protocols, e.g. EM4100, T55xx.
   - Retro computing: Decoders related to retro computing, e.g. MCS-48, Z80.
   - Security/crypto: Decoders related to security or cryptography.
   - Sensor: Decoders for sensors or all kinds, e.g. temperature or humidity.
   - Util: Random utility/helper decoders.
   - Wireless/RF: Decoders related to various wireless/RF technologies, e.g.
     Bluetooth, BLE, Wifi, or 2.4GHz/433MHz custom protocols.


Testsuite
---------

You can run the libsigrokdecode testsuite using:

 $ make check


Protocol decoder test framework
-------------------------------

Please see the sigrok-test repository for a protocol decoder test suite that
checks the decoded data of various PDs against known-good reference data.


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.