Documentation/hwmon/submitting-patches

   1         How to Get Your Patch Accepted Into the Hwmon Subsystem
   2         -------------------------------------------------------
   3
   4 This text is is a collection of suggestions for people writing patches or
   5 drivers for the hwmon subsystem. Following these suggestions will greatly
   6 increase the chances of your change being accepted.
   7
   8
   9 1. General
  10 ----------
  11
  12 * It should be unnecessary to mention, but please read and follow
  13     Documentation/SubmitChecklist
  14     Documentation/SubmittingDrivers
  15     Documentation/SubmittingPatches
  16     Documentation/CodingStyle
  17
  18 * If your patch generates checkpatch warnings, please refrain from explanations
  19   such as "I don't like that coding style". Keep in mind that each unnecessary
  20   warning helps hiding a real problem. If you don't like the kernel coding
  21   style, don't write kernel drivers.
  22
  23 * Please test your patch thoroughly. We are not your test group.
  24   Sometimes a patch can not or not completely be tested because of missing
  25   hardware. In such cases, you should test-build the code on at least one
  26   architecture. If run-time testing was not achieved, it should be written
  27   explicitly below the patch header.
  28
  29 * If your patch (or the driver) is affected by configuration options such as
  30   CONFIG_SMP or CONFIG_HOTPLUG, make sure it compiles for all configuration
  31   variants.
  32
  33
  34 2. Adding functionality to existing drivers
  35 -------------------------------------------
  36
  37 * Make sure the documentation in Documentation/hwmon/<driver_name> is up to
  38   date.
  39
  40 * Make sure the information in Kconfig is up to date.
  41
  42 * If the added functionality requires some cleanup or structural changes, split
  43   your patch into a cleanup part and the actual addition. This makes it easier
  44   to review your changes, and to bisect any resulting problems.
  45
  46 * Never mix bug fixes, cleanup, and functional enhancements in a single patch.
  47
  48
  49 3. New drivers
  50 --------------
  51
  52 * Running your patch or driver file(s) through checkpatch does not mean its
  53   formatting is clean. If unsure about formatting in your new driver, run it
  54   through Lindent. Lindent is not perfect, and you may have to do some minor
  55   cleanup, but it is a good start.
  56
  57 * Consider adding yourself to MAINTAINERS.
  58
  59 * Document the driver in Documentation/hwmon/<driver_name>.
  60
  61 * Add the driver to Kconfig and Makefile in alphabetical order.
  62
  63 * Make sure that all dependencies are listed in Kconfig.
  64
  65 * Avoid forward declarations if you can. Rearrange the code if necessary.
  66
  67 * Avoid calculations in macros and macro-generated functions. While such macros
  68   may save a line or so in the source, it obfuscates the code and makes code
  69   review more difficult. It may also result in code which is more complicated
  70   than necessary. Use inline functions or just regular functions instead.
  71
  72 * Use devres functions whenever possible to allocate resources. For rationale
  73   and supported functions, please see Documentation/driver-model/devres.txt.
  74
  75 * If the driver has a detect function, make sure it is silent. Debug messages
  76   and messages printed after a successful detection are acceptable, but it
  77   must not print messages such as "Chip XXX not found/supported".
  78
  79   Keep in mind that the detect function will run for all drivers supporting an
  80   address if a chip is detected on that address. Unnecessary messages will just
  81   pollute the kernel log and not provide any value.
  82
  83 * Provide a detect function if and only if a chip can be detected reliably.
  84
  85 * Avoid writing to chip registers in the detect function. If you have to write,
  86   only do it after you have already gathered enough data to be certain that the
  87   detection is going to be successful.
  88
  89   Keep in mind that the chip might not be what your driver believes it is, and
  90   writing to it might cause a bad misconfiguration.
  91
  92 * Make sure there are no race conditions in the probe function. Specifically,
  93   completely initialize your chip first, then create sysfs entries and register
  94   with the hwmon subsystem.
  95
  96 * Do not provide support for deprecated sysfs attributes.
  97
  98 * Do not create non-standard attributes unless really needed. If you have to use
  99   non-standard attributes, or you believe you do, discuss it on the mailing list
 100   first. Either case, provide a detailed explanation why you need the
 101   non-standard attribute(s).
 102   Standard attributes are specified in Documentation/hwmon/sysfs-interface.
 103
 104 * When deciding which sysfs attributes to support, look at the chip's
 105   capabilities. While we do not expect your driver to support everything the
 106   chip may offer, it should at least support all limits and alarms.
 107
 108 * Last but not least, please check if a driver for your chip already exists
 109   before starting to write a new driver. Especially for temperature sensors,
 110   new chips are often variants of previously released chips. In some cases,
 111   a presumably new chip may simply have been relabeled.