Adding upstream version 4.19.249.upstream/4.19.249

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 145 insertions, 0 deletions

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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/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.