1	How to Get Your Patch Accepted Into the Hwmon Subsystem
  2	-------------------------------------------------------
  3
  4This text is is a collection of suggestions for people writing patches or
  5drivers for the hwmon subsystem. Following these suggestions will greatly
  6increase the chances of your change being accepted.
  7
  8
  91. 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
 342. 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
 493. 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. For new drivers, it
 64  is most likely prudent to add a dependency on EXPERIMENTAL.
 65
 66* Avoid forward declarations if you can. Rearrange the code if necessary.
 67
 68* Avoid calculations in macros and macro-generated functions. While such macros
 69  may save a line or so in the source, it obfuscates the code and makes code
 70  review more difficult. It may also result in code which is more complicated
 71  than necessary. Use inline functions or just regular functions instead.
 72
 73* If the driver has a detect function, make sure it is silent. Debug messages
 74  and messages printed after a successful detection are acceptable, but it
 75  must not print messages such as "Chip XXX not found/supported".
 76
 77  Keep in mind that the detect function will run for all drivers supporting an
 78  address if a chip is detected on that address. Unnecessary messages will just
 79  pollute the kernel log and not provide any value.
 80
 81* Provide a detect function if and only if a chip can be detected reliably.
 82
 83* Avoid writing to chip registers in the detect function. If you have to write,
 84  only do it after you have already gathered enough data to be certain that the
 85  detection is going to be successful.
 86
 87  Keep in mind that the chip might not be what your driver believes it is, and
 88  writing to it might cause a bad misconfiguration.
 89
 90* Make sure there are no race conditions in the probe function. Specifically,
 91  completely initialize your chip first, then create sysfs entries and register
 92  with the hwmon subsystem.
 93
 94* Do not provide support for deprecated sysfs attributes.
 95
 96* Do not create non-standard attributes unless really needed. If you have to use
 97  non-standard attributes, or you believe you do, discuss it on the mailing list
 98  first. Either case, provide a detailed explanation why you need the
 99  non-standard attribute(s).
100  Standard attributes are specified in Documentation/hwmon/sysfs-interface.
101
102* When deciding which sysfs attributes to support, look at the chip's
103  capabilities. While we do not expect your driver to support everything the
104  chip may offer, it should at least support all limits and alarms.
105
106* Last but not least, please check if a driver for your chip already exists
107  before starting to write a new driver. Especially for temperature sensors,
108  new chips are often variants of previously released chips. In some cases,
109  a presumably new chip may simply have been relabeled.