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Guenter Roeckc3a2f0a2011-04-02 08:26:34 -07001 How to Get Your Patch Accepted Into the Hwmon Subsystem
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Masanari Iidaac20ad12013-08-20 05:53:49 -07004This text is a collection of suggestions for people writing patches or
Guenter Roeckc3a2f0a2011-04-02 08:26:34 -07005drivers for the hwmon subsystem. Following these suggestions will greatly
6increase the chances of your change being accepted.
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91. General
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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
Stephen Rothwell40b31362013-05-21 13:49:35 +100030 CONFIG_SMP, make sure it compiles for all configuration variants.
Guenter Roeckc3a2f0a2011-04-02 08:26:34 -070031
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332. Adding functionality to existing drivers
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35
36* Make sure the documentation in Documentation/hwmon/<driver_name> is up to
37 date.
38
39* Make sure the information in Kconfig is up to date.
40
41* If the added functionality requires some cleanup or structural changes, split
42 your patch into a cleanup part and the actual addition. This makes it easier
43 to review your changes, and to bisect any resulting problems.
44
45* Never mix bug fixes, cleanup, and functional enhancements in a single patch.
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483. New drivers
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50
51* Running your patch or driver file(s) through checkpatch does not mean its
52 formatting is clean. If unsure about formatting in your new driver, run it
53 through Lindent. Lindent is not perfect, and you may have to do some minor
54 cleanup, but it is a good start.
55
56* Consider adding yourself to MAINTAINERS.
57
58* Document the driver in Documentation/hwmon/<driver_name>.
59
60* Add the driver to Kconfig and Makefile in alphabetical order.
61
Kees Cook07d33602012-10-02 11:16:18 -070062* Make sure that all dependencies are listed in Kconfig.
Guenter Roeckc3a2f0a2011-04-02 08:26:34 -070063
64* Avoid forward declarations if you can. Rearrange the code if necessary.
65
66* Avoid calculations in macros and macro-generated functions. While such macros
67 may save a line or so in the source, it obfuscates the code and makes code
68 review more difficult. It may also result in code which is more complicated
69 than necessary. Use inline functions or just regular functions instead.
70
Guenter Roeck3fafb0c2012-06-16 07:33:52 -070071* Use devres functions whenever possible to allocate resources. For rationale
72 and supported functions, please see Documentation/driver-model/devres.txt.
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Guenter Roeckc3a2f0a2011-04-02 08:26:34 -070074* If the driver has a detect function, make sure it is silent. Debug messages
75 and messages printed after a successful detection are acceptable, but it
76 must not print messages such as "Chip XXX not found/supported".
77
78 Keep in mind that the detect function will run for all drivers supporting an
79 address if a chip is detected on that address. Unnecessary messages will just
80 pollute the kernel log and not provide any value.
81
82* Provide a detect function if and only if a chip can be detected reliably.
83
Jean Delvare97607f92015-07-03 14:39:05 +020084* Only the following I2C addresses shall be probed: 0x18-0x1f, 0x28-0x2f,
85 0x48-0x4f, 0x58, 0x5c, 0x73 and 0x77. Probing other addresses is strongly
86 discouraged as it is known to cause trouble with other (non-hwmon) I2C
87 chips. If your chip lives at an address which can't be probed then the
88 device will have to be instantiated explicitly (which is always better
89 anyway.)
90
Guenter Roeckc3a2f0a2011-04-02 08:26:34 -070091* Avoid writing to chip registers in the detect function. If you have to write,
92 only do it after you have already gathered enough data to be certain that the
93 detection is going to be successful.
94
95 Keep in mind that the chip might not be what your driver believes it is, and
96 writing to it might cause a bad misconfiguration.
97
98* Make sure there are no race conditions in the probe function. Specifically,
99 completely initialize your chip first, then create sysfs entries and register
100 with the hwmon subsystem.
101
102* Do not provide support for deprecated sysfs attributes.
103
104* Do not create non-standard attributes unless really needed. If you have to use
105 non-standard attributes, or you believe you do, discuss it on the mailing list
106 first. Either case, provide a detailed explanation why you need the
107 non-standard attribute(s).
108 Standard attributes are specified in Documentation/hwmon/sysfs-interface.
109
110* When deciding which sysfs attributes to support, look at the chip's
111 capabilities. While we do not expect your driver to support everything the
112 chip may offer, it should at least support all limits and alarms.
113
114* Last but not least, please check if a driver for your chip already exists
115 before starting to write a new driver. Especially for temperature sensors,
116 new chips are often variants of previously released chips. In some cases,
117 a presumably new chip may simply have been relabeled.