Documentation/SubmittingDrivers

   1 Submitting Drivers For The Linux Kernel
   2 =======================================
   3
   4 This document is intended to explain how to submit device drivers to the
   5 various kernel trees. Note that if you are interested in video card drivers
   6 you should probably talk to XFree86 (http://www.xfree86.org/) and/or X.Org
   7 (http://x.org/) instead.
   8
   9 Also read the Documentation/SubmittingPatches document.
  10
  11
  12 Allocating Device Numbers
  13 -------------------------
  14
  15 Major and minor numbers for block and character devices are allocated
  16 by the Linux assigned name and number authority (currently this is
  17 Torben Mathiasen). The site is http://www.lanana.org/. This
  18 also deals with allocating numbers for devices that are not going to
  19 be submitted to the mainstream kernel.
  20 See Documentation/devices.txt for more information on this.
  21
  22 If you don't use assigned numbers then when your device is submitted it will
  23 be given an assigned number even if that is different from values you may
  24 have shipped to customers before.
  25
  26 Who To Submit Drivers To
  27 ------------------------
  28
  29 Linux 2.0:
  30         No new drivers are accepted for this kernel tree.
  31
  32 Linux 2.2:
  33         No new drivers are accepted for this kernel tree.
  34
  35 Linux 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
  41 Linux 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
  46 What Criteria Determine Acceptance
  47 ----------------------------------
  48
  49 Licensing:
  50                 The code must be released to us under the
  51                 GNU General Public License. We don't insist on any kind
  52                 of exclusive GPL licensing, and if you wish the driver
  53                 to be useful to other communities such as BSD you may well
  54                 wish to release under multiple licenses.
  55                 See accepted licenses at include/linux/module.h
  56
  57 Copyright:
  58                 The copyright owner must agree to use of GPL.
  59                 It's best if the submitter and copyright owner
  60                 are the same person/entity. If not, the name of
  61                 the person/entity authorizing use of GPL should be
  62                 listed in case it's necessary to verify the will of
  63                 the copyright owner.
  64
  65 Interfaces:
  66                 If your driver uses existing interfaces and behaves like
  67                 other drivers in the same class it will be much more likely
  68                 to be accepted than if it invents gratuitous new ones.
  69                 If you need to implement a common API over Linux and NT
  70                 drivers do it in userspace.
  71
  72 Code:
  73                 Please use the Linux style of code formatting as documented
  74                 in Documentation/CodingStyle. If you have sections of code
  75                 that need to be in other formats, for example because they
  76                 are shared with a windows driver kit and you want to
  77                 maintain them just once separate them out nicely and note
  78                 this fact.
  79
  80 Portability:
  81                 Pointers are not always 32bits, not all computers are little
  82                 endian, people do not all have floating point and you
  83                 shouldn't use inline x86 assembler in your driver without
  84                 careful thought. Pure x86 drivers generally are not popular.
  85                 If you only have x86 hardware it is hard to test portability
  86                 but it is easy to make sure the code can easily be made
  87                 portable.
  88
  89 Clarity:
  90                 It helps if anyone can see how to fix the driver. It helps
  91                 you because you get patches not bug reports. If you submit a
  92                 driver that intentionally obfuscates how the hardware works
  93                 it will go in the bitbucket.
  94
  95 PM support:
  96                 Since Linux is used on many portable and desktop systems, your
  97                 driver is likely to be used on such a system and therefore it
  98                 should support basic power management by implementing, if
  99                 necessary, the .suspend and .resume methods used during the
 100                 system-wide suspend and resume transitions.  You should verify
 101                 that your driver correctly handles the suspend and resume, but
 102                 if you are unable to ensure that, please at least define the
 103                 .suspend method returning the -ENOSYS ("Function not
 104                 implemented") error.  You should also try to make sure that your
 105                 driver uses as little power as possible when it's not doing
 106                 anything.  For the driver testing instructions see
 107                 Documentation/power/drivers-testing.txt and for a relatively
 108                 complete overview of the power management issues related to
 109                 drivers see Documentation/power/devices.txt .
 110
 111 Control:
 112                 In general if there is active maintenance of a driver by
 113                 the author then patches will be redirected to them unless
 114                 they are totally obvious and without need of checking.
 115                 If you want to be the contact and update point for the
 116                 driver it is a good idea to state this in the comments,
 117                 and include an entry in MAINTAINERS for your driver.
 118
 119 What Criteria Do Not Determine Acceptance
 120 -----------------------------------------
 121
 122 Vendor:
 123                 Being the hardware vendor and maintaining the driver is
 124                 often a good thing. If there is a stable working driver from
 125                 other people already in the tree don't expect 'we are the
 126                 vendor' to get your driver chosen. Ideally work with the
 127                 existing driver author to build a single perfect driver.
 128
 129 Author:
 130                 It doesn't matter if a large Linux company wrote the driver,
 131                 or you did. Nobody has any special access to the kernel
 132                 tree. Anyone who tells you otherwise isn't telling the
 133                 whole story.
 134
 135
 136 Resources
 137 ---------
 138
 139 Linux kernel master tree:
 140         ftp.\ *country_code*\ .kernel.org:/pub/linux/kernel/...
 141
 142         where *country_code* == your country code, such as
 143         **us**, **uk**, **fr**, etc.
 144
 145         http://git.kernel.org/?p=linux/kernel/git/torvalds/linux.git
 146
 147 Linux kernel mailing list:
 148         linux-kernel@vger.kernel.org
 149         [mail majordomo@vger.kernel.org to subscribe]
 150
 151 Linux Device Drivers, Third Edition (covers 2.6.10):
 152         http://lwn.net/Kernel/LDD3/  (free version)
 153
 154 LWN.net:
 155         Weekly summary of kernel development activity - http://lwn.net/
 156
 157         2.6 API changes:
 158
 159                 http://lwn.net/Articles/2.6-kernel-api/
 160
 161         Porting drivers from prior kernels to 2.6:
 162
 163                 http://lwn.net/Articles/driver-porting/
 164
 165 KernelNewbies:
 166         Documentation and assistance for new kernel programmers
 167
 168                 http://kernelnewbies.org/
 169
 170 Linux USB project:
 171         http://www.linux-usb.org/
 172
 173 How to NOT write kernel driver by Arjan van de Ven:
 174         http://www.fenrus.org/how-to-not-write-a-device-driver-paper.pdf
 175
 176 Kernel Janitor:
 177         http://kernelnewbies.org/KernelJanitors
 178
 179 GIT, Fast Version Control System:
 180         http://git-scm.com/