Documentation/process/submitting-drivers.rst

   1 .. _submittingdrivers:
   2
   3 Submitting Drivers For The Linux Kernel
   4 =======================================
   5
   6 This document is intended to explain how to submit device drivers to the
   7 various kernel trees. Note that if you are interested in video card drivers
   8 you should probably talk to XFree86 (http://www.xfree86.org/) and/or X.Org
   9 (http://x.org/) instead.
  10
  11 .. note::
  12
  13    This document is old and has seen little maintenance in recent years; it
  14    should probably be updated or, perhaps better, just deleted.  Most of
  15    what is here can be found in the other development documents anyway.
  16
  17    Oh, and we don't really recommend submitting changes to XFree86 :)
  18
  19 Also read the Documentation/process/submitting-patches.rst document.
  20
  21
  22 Allocating Device Numbers
  23 -------------------------
  24
  25 Major and minor numbers for block and character devices are allocated
  26 by the Linux assigned name and number authority (currently this is
  27 Torben Mathiasen). The site is http://www.lanana.org/. This
  28 also deals with allocating numbers for devices that are not going to
  29 be submitted to the mainstream kernel.
  30 See Documentation/admin-guide/devices.rst for more information on this.
  31
  32 If you don't use assigned numbers then when your device is submitted it will
  33 be given an assigned number even if that is different from values you may
  34 have shipped to customers before.
  35
  36 Who To Submit Drivers To
  37 ------------------------
  38
  39 Linux 2.0:
  40         No new drivers are accepted for this kernel tree.
  41
  42 Linux 2.2:
  43         No new drivers are accepted for this kernel tree.
  44
  45 Linux 2.4:
  46         If the code area has a general maintainer then please submit it to
  47         the maintainer listed in MAINTAINERS in the kernel file. If the
  48         maintainer does not respond or you cannot find the appropriate
  49         maintainer then please contact Willy Tarreau <w@1wt.eu>.
  50
  51 Linux 2.6 and upper:
  52         The same rules apply as 2.4 except that you should follow linux-kernel
  53         to track changes in API's. The final contact point for Linux 2.6+
  54         submissions is Andrew Morton.
  55
  56 What Criteria Determine Acceptance
  57 ----------------------------------
  58
  59 Licensing:
  60                 The code must be released to us under the
  61                 GNU General Public License. We don't insist on any kind
  62                 of exclusive GPL licensing, and if you wish the driver
  63                 to be useful to other communities such as BSD you may well
  64                 wish to release under multiple licenses.
  65                 See accepted licenses at include/linux/module.h
  66
  67 Copyright:
  68                 The copyright owner must agree to use of GPL.
  69                 It's best if the submitter and copyright owner
  70                 are the same person/entity. If not, the name of
  71                 the person/entity authorizing use of GPL should be
  72                 listed in case it's necessary to verify the will of
  73                 the copyright owner.
  74
  75 Interfaces:
  76                 If your driver uses existing interfaces and behaves like
  77                 other drivers in the same class it will be much more likely
  78                 to be accepted than if it invents gratuitous new ones.
  79                 If you need to implement a common API over Linux and NT
  80                 drivers do it in userspace.
  81
  82 Code:
  83                 Please use the Linux style of code formatting as documented
  84                 in :ref:`Documentation/process/coding-style.rst <codingStyle>`.
  85                 If you have sections of code
  86                 that need to be in other formats, for example because they
  87                 are shared with a windows driver kit and you want to
  88                 maintain them just once separate them out nicely and note
  89                 this fact.
  90
  91 Portability:
  92                 Pointers are not always 32bits, not all computers are little
  93                 endian, people do not all have floating point and you
  94                 shouldn't use inline x86 assembler in your driver without
  95                 careful thought. Pure x86 drivers generally are not popular.
  96                 If you only have x86 hardware it is hard to test portability
  97                 but it is easy to make sure the code can easily be made
  98                 portable.
  99
 100 Clarity:
 101                 It helps if anyone can see how to fix the driver. It helps
 102                 you because you get patches not bug reports. If you submit a
 103                 driver that intentionally obfuscates how the hardware works
 104                 it will go in the bitbucket.
 105
 106 PM support:
 107                 Since Linux is used on many portable and desktop systems, your
 108                 driver is likely to be used on such a system and therefore it
 109                 should support basic power management by implementing, if
 110                 necessary, the .suspend and .resume methods used during the
 111                 system-wide suspend and resume transitions.  You should verify
 112                 that your driver correctly handles the suspend and resume, but
 113                 if you are unable to ensure that, please at least define the
 114                 .suspend method returning the -ENOSYS ("Function not
 115                 implemented") error.  You should also try to make sure that your
 116                 driver uses as little power as possible when it's not doing
 117                 anything.  For the driver testing instructions see
 118                 Documentation/power/drivers-testing.txt and for a relatively
 119                 complete overview of the power management issues related to
 120                 drivers see Documentation/power/admin-guide/devices.rst .
 121
 122 Control:
 123                 In general if there is active maintenance of a driver by
 124                 the author then patches will be redirected to them unless
 125                 they are totally obvious and without need of checking.
 126                 If you want to be the contact and update point for the
 127                 driver it is a good idea to state this in the comments,
 128                 and include an entry in MAINTAINERS for your driver.
 129
 130 What Criteria Do Not Determine Acceptance
 131 -----------------------------------------
 132
 133 Vendor:
 134                 Being the hardware vendor and maintaining the driver is
 135                 often a good thing. If there is a stable working driver from
 136                 other people already in the tree don't expect 'we are the
 137                 vendor' to get your driver chosen. Ideally work with the
 138                 existing driver author to build a single perfect driver.
 139
 140 Author:
 141                 It doesn't matter if a large Linux company wrote the driver,
 142                 or you did. Nobody has any special access to the kernel
 143                 tree. Anyone who tells you otherwise isn't telling the
 144                 whole story.
 145
 146
 147 Resources
 148 ---------
 149
 150 Linux kernel master tree:
 151         ftp.\ *country_code*\ .kernel.org:/pub/linux/kernel/...
 152
 153         where *country_code* == your country code, such as
 154         **us**, **uk**, **fr**, etc.
 155
 156         http://git.kernel.org/?p=linux/kernel/git/torvalds/linux.git
 157
 158 Linux kernel mailing list:
 159         linux-kernel@vger.kernel.org
 160         [mail majordomo@vger.kernel.org to subscribe]
 161
 162 Linux Device Drivers, Third Edition (covers 2.6.10):
 163         http://lwn.net/Kernel/LDD3/  (free version)
 164
 165 LWN.net:
 166         Weekly summary of kernel development activity - http://lwn.net/
 167
 168         2.6 API changes:
 169
 170                 http://lwn.net/Articles/2.6-kernel-api/
 171
 172         Porting drivers from prior kernels to 2.6:
 173
 174                 http://lwn.net/Articles/driver-porting/
 175
 176 KernelNewbies:
 177         Documentation and assistance for new kernel programmers
 178
 179                 http://kernelnewbies.org/
 180
 181 Linux USB project:
 182         http://www.linux-usb.org/
 183
 184 How to NOT write kernel driver by Arjan van de Ven:
 185         http://www.fenrus.org/how-to-not-write-a-device-driver-paper.pdf
 186
 187 Kernel Janitor:
 188         http://kernelnewbies.org/KernelJanitors
 189
 190 GIT, Fast Version Control System:
 191         http://git-scm.com/