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diff --git a/Documentation/hwmon/submitting-patches b/Documentation/hwmon/submitting-patches new file mode 100644 index 000000000..f88221b46 --- /dev/null +++ b/Documentation/hwmon/submitting-patches @@ -0,0 +1,145 @@ + 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/process/submit-checklist.rst + Documentation/process/submitting-drivers.rst + Documentation/process/submitting-patches.rst + Documentation/process/coding-style.rst + +* Please run your patch through 'checkpatch --strict'. There should be no + errors, no warnings, and few if any check messages. If there are any + messages, please be prepared to explain. + +* If your patch generates checkpatch errors, warnings, or check messages, + please refrain from explanations such as "I prefer that coding style". + Keep in mind that each unnecessary message helps hiding a real problem, + and a consistent coding style makes it easier for others to understand + and review the code. + +* 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. + +* Please list include files in alphabetic order. + +* Please align continuation lines with '(' on the previous line. + +* Avoid forward declarations if you can. Rearrange the code if necessary. + +* Avoid macros to generate groups of sensor attributes. It not only confuses + checkpatch, but also makes it more difficult to review the code. + +* 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. + +* Limit the number of kernel log messages. In general, your driver should not + generate an error message just because a runtime operation failed. Report + errors to user space instead, using an appropriate error code. Keep in mind + that kernel error log messages not only fill up the kernel log, but also are + printed synchronously, most likely with interrupt disabled, often to a serial + console. Excessive logging can seriously affect system performance. + +* Use devres functions whenever possible to allocate resources. For rationale + and supported functions, please see Documentation/driver-model/devres.txt. + If a function is not supported by devres, consider using devm_add_action(). + +* 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 and your driver first, then register with + the hwmon subsystem. + +* Use devm_hwmon_device_register_with_groups() or, if your driver needs a remove + function, hwmon_device_register_with_groups() to register your driver with the + hwmon subsystem. Try using devm_add_action() instead of a remove function if + possible. Do not use hwmon_device_register(). + +* Your driver should be buildable as module. If not, please be prepared to + explain why it has to be built into the kernel. + +* 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. |