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- How to Get Your Patch Accepted Into the Hwmon Subsystem
- -------------------------------------------------------
- This text is a collection of suggestions for people writing patches or
- drivers for the hwmon subsystem. Following these suggestions will greatly
- increase the chances of your change being accepted.
- 1. General
- ----------
- * It should be unnecessary to mention, but please read and follow
- Documentation/SubmitChecklist
- Documentation/SubmittingDrivers
- Documentation/SubmittingPatches
- Documentation/CodingStyle
- * If your patch generates checkpatch warnings, please refrain from explanations
- such as "I don't like that coding style". Keep in mind that each unnecessary
- warning helps hiding a real problem. If you don't like the kernel coding
- style, don't write kernel drivers.
- * Please test your patch thoroughly. We are not your test group.
- Sometimes a patch can not or not completely be tested because of missing
- hardware. In such cases, you should test-build the code on at least one
- architecture. If run-time testing was not achieved, it should be written
- explicitly below the patch header.
- * If your patch (or the driver) is affected by configuration options such as
- CONFIG_SMP, make sure it compiles for all configuration variants.
- 2. Adding functionality to existing drivers
- -------------------------------------------
- * Make sure the documentation in Documentation/hwmon/<driver_name> is up to
- date.
- * Make sure the information in Kconfig is up to date.
- * If the added functionality requires some cleanup or structural changes, split
- your patch into a cleanup part and the actual addition. This makes it easier
- to review your changes, and to bisect any resulting problems.
- * Never mix bug fixes, cleanup, and functional enhancements in a single patch.
- 3. New drivers
- --------------
- * Running your patch or driver file(s) through checkpatch does not mean its
- formatting is clean. If unsure about formatting in your new driver, run it
- through Lindent. Lindent is not perfect, and you may have to do some minor
- cleanup, but it is a good start.
- * Consider adding yourself to MAINTAINERS.
- * Document the driver in Documentation/hwmon/<driver_name>.
- * Add the driver to Kconfig and Makefile in alphabetical order.
- * Make sure that all dependencies are listed in Kconfig.
- * Avoid forward declarations if you can. Rearrange the code if necessary.
- * Avoid calculations in macros and macro-generated functions. While such macros
- may save a line or so in the source, it obfuscates the code and makes code
- review more difficult. It may also result in code which is more complicated
- than necessary. Use inline functions or just regular functions instead.
- * Use devres functions whenever possible to allocate resources. For rationale
- and supported functions, please see Documentation/driver-model/devres.txt.
- * If the driver has a detect function, make sure it is silent. Debug messages
- and messages printed after a successful detection are acceptable, but it
- must not print messages such as "Chip XXX not found/supported".
- Keep in mind that the detect function will run for all drivers supporting an
- address if a chip is detected on that address. Unnecessary messages will just
- pollute the kernel log and not provide any value.
- * Provide a detect function if and only if a chip can be detected reliably.
- * Only the following I2C addresses shall be probed: 0x18-0x1f, 0x28-0x2f,
- 0x48-0x4f, 0x58, 0x5c, 0x73 and 0x77. Probing other addresses is strongly
- discouraged as it is known to cause trouble with other (non-hwmon) I2C
- chips. If your chip lives at an address which can't be probed then the
- device will have to be instantiated explicitly (which is always better
- anyway.)
- * Avoid writing to chip registers in the detect function. If you have to write,
- only do it after you have already gathered enough data to be certain that the
- detection is going to be successful.
- Keep in mind that the chip might not be what your driver believes it is, and
- writing to it might cause a bad misconfiguration.
- * Make sure there are no race conditions in the probe function. Specifically,
- completely initialize your chip first, then create sysfs entries and register
- with the hwmon subsystem.
- * Do not provide support for deprecated sysfs attributes.
- * Do not create non-standard attributes unless really needed. If you have to use
- non-standard attributes, or you believe you do, discuss it on the mailing list
- first. Either case, provide a detailed explanation why you need the
- non-standard attribute(s).
- Standard attributes are specified in Documentation/hwmon/sysfs-interface.
- * When deciding which sysfs attributes to support, look at the chip's
- capabilities. While we do not expect your driver to support everything the
- chip may offer, it should at least support all limits and alarms.
- * Last but not least, please check if a driver for your chip already exists
- before starting to write a new driver. Especially for temperature sensors,
- new chips are often variants of previously released chips. In some cases,
- a presumably new chip may simply have been relabeled.
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