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hwmon: Add submitting-patches checklist to documentation
When writing hardware monitoring drivers, there are some common pitfalls which keep coming up in code reviews. This patch provides a document describing all those pitfalls and how to avoid them. Signed-off-by: Guenter Roeck <[email protected]> Acked-by: Jean Delvare <[email protected]>
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Apr 19, 2011
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How to Get Your Patch Accepted Into the Hwmon Subsystem | ||
------------------------------------------------------- | ||
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This text is 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. | ||
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1. General | ||
---------- | ||
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* It should be unnecessary to mention, but please read and follow | ||
Documentation/SubmitChecklist | ||
Documentation/SubmittingDrivers | ||
Documentation/SubmittingPatches | ||
Documentation/CodingStyle | ||
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* 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. | ||
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* 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. | ||
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* If your patch (or the driver) is affected by configuration options such as | ||
CONFIG_SMP or CONFIG_HOTPLUG, make sure it compiles for all configuration | ||
variants. | ||
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2. Adding functionality to existing drivers | ||
------------------------------------------- | ||
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* Make sure the documentation in Documentation/hwmon/<driver_name> is up to | ||
date. | ||
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* Make sure the information in Kconfig is up to date. | ||
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* 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. | ||
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* Never mix bug fixes, cleanup, and functional enhancements in a single patch. | ||
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3. New drivers | ||
-------------- | ||
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* 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. | ||
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* Consider adding yourself to MAINTAINERS. | ||
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* Document the driver in Documentation/hwmon/<driver_name>. | ||
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* Add the driver to Kconfig and Makefile in alphabetical order. | ||
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* Make sure that all dependencies are listed in Kconfig. For new drivers, it | ||
is most likely prudent to add a dependency on EXPERIMENTAL. | ||
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* Avoid forward declarations if you can. Rearrange the code if necessary. | ||
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* 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. | ||
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* 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". | ||
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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. | ||
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* Provide a detect function if and only if a chip can be detected reliably. | ||
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* 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. | ||
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Keep in mind that the chip might not be what your driver believes it is, and | ||
writing to it might cause a bad misconfiguration. | ||
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* 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. | ||
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* Do not provide support for deprecated sysfs attributes. | ||
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* 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. | ||
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* 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. | ||
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* 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. |