Root/Documentation/SubmittingDrivers

1Submitting Drivers For The Linux Kernel
2---------------------------------------
3
4This document is intended to explain how to submit device drivers to the
5various kernel trees. Note that if you are interested in video card drivers
6you should probably talk to XFree86 (http://www.xfree86.org/) and/or X.Org
7(http://x.org/) instead.
8
9Also read the Documentation/SubmittingPatches document.
10
11
12Allocating Device Numbers
13-------------------------
14
15Major and minor numbers for block and character devices are allocated
16by the Linux assigned name and number authority (currently this is
17Torben Mathiasen). The site is http://www.lanana.org/. This
18also deals with allocating numbers for devices that are not going to
19be submitted to the mainstream kernel.
20See Documentation/devices.txt for more information on this.
21
22If you don't use assigned numbers then when your device is submitted it will
23be given an assigned number even if that is different from values you may
24have shipped to customers before.
25
26Who To Submit Drivers To
27------------------------
28
29Linux 2.0:
30    No new drivers are accepted for this kernel tree.
31
32Linux 2.2:
33    No new drivers are accepted for this kernel tree.
34
35Linux 2.4:
36    If the code area has a general maintainer then please submit it to
37    the maintainer listed in MAINTAINERS in the kernel file. If the
38    maintainer does not respond or you cannot find the appropriate
39    maintainer then please contact Willy Tarreau <w@1wt.eu>.
40
41Linux 2.6:
42    The same rules apply as 2.4 except that you should follow linux-kernel
43    to track changes in API's. The final contact point for Linux 2.6
44    submissions is Andrew Morton.
45
46What Criteria Determine Acceptance
47----------------------------------
48
49Licensing: The code must be released to us under the
50        GNU General Public License. We don't insist on any kind
51        of exclusive GPL licensing, and if you wish the driver
52        to be useful to other communities such as BSD you may well
53        wish to release under multiple licenses.
54        See accepted licenses at include/linux/module.h
55
56Copyright: The copyright owner must agree to use of GPL.
57        It's best if the submitter and copyright owner
58        are the same person/entity. If not, the name of
59        the person/entity authorizing use of GPL should be
60        listed in case it's necessary to verify the will of
61        the copyright owner.
62
63Interfaces: If your driver uses existing interfaces and behaves like
64        other drivers in the same class it will be much more likely
65        to be accepted than if it invents gratuitous new ones.
66        If you need to implement a common API over Linux and NT
67        drivers do it in userspace.
68
69Code: Please use the Linux style of code formatting as documented
70        in Documentation/CodingStyle. If you have sections of code
71        that need to be in other formats, for example because they
72        are shared with a windows driver kit and you want to
73        maintain them just once separate them out nicely and note
74        this fact.
75
76Portability: Pointers are not always 32bits, not all computers are little
77        endian, people do not all have floating point and you
78        shouldn't use inline x86 assembler in your driver without
79        careful thought. Pure x86 drivers generally are not popular.
80        If you only have x86 hardware it is hard to test portability
81        but it is easy to make sure the code can easily be made
82        portable.
83
84Clarity: It helps if anyone can see how to fix the driver. It helps
85        you because you get patches not bug reports. If you submit a
86        driver that intentionally obfuscates how the hardware works
87        it will go in the bitbucket.
88
89PM support: Since Linux is used on many portable and desktop systems, your
90        driver is likely to be used on such a system and therefore it
91        should support basic power management by implementing, if
92        necessary, the .suspend and .resume methods used during the
93        system-wide suspend and resume transitions. You should verify
94        that your driver correctly handles the suspend and resume, but
95        if you are unable to ensure that, please at least define the
96        .suspend method returning the -ENOSYS ("Function not
97        implemented") error. You should also try to make sure that your
98        driver uses as little power as possible when it's not doing
99        anything. For the driver testing instructions see
100        Documentation/power/drivers-testing.txt and for a relatively
101        complete overview of the power management issues related to
102        drivers see Documentation/power/devices.txt .
103
104Control: In general if there is active maintenance of a driver by
105        the author then patches will be redirected to them unless
106        they are totally obvious and without need of checking.
107        If you want to be the contact and update point for the
108        driver it is a good idea to state this in the comments,
109        and include an entry in MAINTAINERS for your driver.
110
111What Criteria Do Not Determine Acceptance
112-----------------------------------------
113
114Vendor: Being the hardware vendor and maintaining the driver is
115        often a good thing. If there is a stable working driver from
116        other people already in the tree don't expect 'we are the
117        vendor' to get your driver chosen. Ideally work with the
118        existing driver author to build a single perfect driver.
119
120Author: It doesn't matter if a large Linux company wrote the driver,
121        or you did. Nobody has any special access to the kernel
122        tree. Anyone who tells you otherwise isn't telling the
123        whole story.
124
125
126Resources
127---------
128
129Linux kernel master tree:
130    ftp.??.kernel.org:/pub/linux/kernel/...
131    ?? == your country code, such as "us", "uk", "fr", etc.
132
133    http://git.kernel.org/?p=linux/kernel/git/torvalds/linux.git
134
135Linux kernel mailing list:
136    linux-kernel@vger.kernel.org
137    [mail majordomo@vger.kernel.org to subscribe]
138
139Linux Device Drivers, Third Edition (covers 2.6.10):
140    http://lwn.net/Kernel/LDD3/ (free version)
141
142LWN.net:
143    Weekly summary of kernel development activity - http://lwn.net/
144    2.6 API changes:
145        http://lwn.net/Articles/2.6-kernel-api/
146    Porting drivers from prior kernels to 2.6:
147        http://lwn.net/Articles/driver-porting/
148
149KernelTrap:
150    Occasional Linux kernel articles and developer interviews
151    http://kerneltrap.org/
152
153KernelNewbies:
154    Documentation and assistance for new kernel programmers
155    http://kernelnewbies.org/
156
157Linux USB project:
158    http://www.linux-usb.org/
159
160How to NOT write kernel driver by Arjan van de Ven:
161    http://www.fenrus.org/how-to-not-write-a-device-driver-paper.pdf
162
163Kernel Janitor:
164    http://kernelnewbies.org/KernelJanitors
165
166GIT, Fast Version Control System:
167    http://git-scm.com/
168

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