.. _submittingdrivers:

  Submitting Drivers For The Linux Kernel

  =======================================

  
  This document is intended to explain how to submit device drivers to the
  various kernel trees. Note that if you are interested in video card drivers
  you should probably talk to XFree86 (http://www.xfree86.org/) and/or X.Org
  (http://x.org/) instead.
  
  Also read the Documentation/SubmittingPatches document.
  
  
  Allocating Device Numbers
  -------------------------
  
  Major and minor numbers for block and character devices are allocated

  by the Linux assigned name and number authority (currently this is
  Torben Mathiasen). The site is http://www.lanana.org/. This

  also deals with allocating numbers for devices that are not going to
  be submitted to the mainstream kernel.

  See Documentation/devices.txt for more information on this.

  If you don't use assigned numbers then when your device is submitted it will
  be given an assigned number even if that is different from values you may

  have shipped to customers before.
  
  Who To Submit Drivers To
  ------------------------
  
  Linux 2.0:

  	No new drivers are accepted for this kernel tree.

  
  Linux 2.2:

  	No new drivers are accepted for this kernel tree.
  
  Linux 2.4:

  	If the code area has a general maintainer then please submit it to
  	the maintainer listed in MAINTAINERS in the kernel file. If the
  	maintainer does not respond or you cannot find the appropriate

  	maintainer then please contact Willy Tarreau <w@1wt.eu>.

  Linux 2.6 and upper:

  	The same rules apply as 2.4 except that you should follow linux-kernel

  	to track changes in API's. The final contact point for Linux 2.6+

  	submissions is Andrew Morton.

  
  What Criteria Determine Acceptance
  ----------------------------------

  Licensing:
  		The code must be released to us under the

  		GNU General Public License. We don't insist on any kind

  		of exclusive GPL licensing, and if you wish the driver

  		to be useful to other communities such as BSD you may well
  		wish to release under multiple licenses.

  		See accepted licenses at include/linux/module.h

  Copyright:
  		The copyright owner must agree to use of GPL.

  		It's best if the submitter and copyright owner
  		are the same person/entity. If not, the name of
  		the person/entity authorizing use of GPL should be
  		listed in case it's necessary to verify the will of

  		the copyright owner.

  Interfaces:
  		If your driver uses existing interfaces and behaves like

  		other drivers in the same class it will be much more likely

  		to be accepted than if it invents gratuitous new ones.

  		If you need to implement a common API over Linux and NT
  		drivers do it in userspace.

  Code:
  		Please use the Linux style of code formatting as documented

  		in :ref:`Documentation/CodingStyle <codingStyle>`.
  		If you have sections of code

  		that need to be in other formats, for example because they
  		are shared with a windows driver kit and you want to
  		maintain them just once separate them out nicely and note
  		this fact.

  Portability:
  		Pointers are not always 32bits, not all computers are little

  		endian, people do not all have floating point and you
  		shouldn't use inline x86 assembler in your driver without
  		careful thought. Pure x86 drivers generally are not popular.
  		If you only have x86 hardware it is hard to test portability
  		but it is easy to make sure the code can easily be made
  		portable.

  Clarity:
  		It helps if anyone can see how to fix the driver. It helps

  		you because you get patches not bug reports. If you submit a
  		driver that intentionally obfuscates how the hardware works
  		it will go in the bitbucket.

  PM support:
  		Since Linux is used on many portable and desktop systems, your

  		driver is likely to be used on such a system and therefore it
  		should support basic power management by implementing, if
  		necessary, the .suspend and .resume methods used during the
  		system-wide suspend and resume transitions.  You should verify
  		that your driver correctly handles the suspend and resume, but
  		if you are unable to ensure that, please at least define the
  		.suspend method returning the -ENOSYS ("Function not
  		implemented") error.  You should also try to make sure that your
  		driver uses as little power as possible when it's not doing
  		anything.  For the driver testing instructions see
  		Documentation/power/drivers-testing.txt and for a relatively
  		complete overview of the power management issues related to
  		drivers see Documentation/power/devices.txt .

  Control:
  		In general if there is active maintenance of a driver by

  		the author then patches will be redirected to them unless

  		they are totally obvious and without need of checking.
  		If you want to be the contact and update point for the
  		driver it is a good idea to state this in the comments,
  		and include an entry in MAINTAINERS for your driver.
  
  What Criteria Do Not Determine Acceptance
  -----------------------------------------

  Vendor:
  		Being the hardware vendor and maintaining the driver is

  		often a good thing. If there is a stable working driver from
  		other people already in the tree don't expect 'we are the

  		vendor' to get your driver chosen. Ideally work with the

  		existing driver author to build a single perfect driver.

  Author:
  		It doesn't matter if a large Linux company wrote the driver,

  		or you did. Nobody has any special access to the kernel
  		tree. Anyone who tells you otherwise isn't telling the
  		whole story.
  
  
  Resources
  ---------
  
  Linux kernel master tree:

  	ftp.\ *country_code*\ .kernel.org:/pub/linux/kernel/...
  
  	where *country_code* == your country code, such as
  	**us**, **uk**, **fr**, etc.

  	http://git.kernel.org/?p=linux/kernel/git/torvalds/linux.git

  Linux kernel mailing list:

  	linux-kernel@vger.kernel.org
  	[mail majordomo@vger.kernel.org to subscribe]
  
  Linux Device Drivers, Third Edition (covers 2.6.10):
  	http://lwn.net/Kernel/LDD3/  (free version)

  LWN.net:
  	Weekly summary of kernel development activity - http://lwn.net/

  	2.6 API changes:

  		http://lwn.net/Articles/2.6-kernel-api/

  	Porting drivers from prior kernels to 2.6:

  		http://lwn.net/Articles/driver-porting/

  KernelNewbies:
  	Documentation and assistance for new kernel programmers

  
  		http://kernelnewbies.org/

  
  Linux USB project:

  	http://www.linux-usb.org/

  How to NOT write kernel driver by Arjan van de Ven:
  	http://www.fenrus.org/how-to-not-write-a-device-driver-paper.pdf

  
  Kernel Janitor:

  	http://kernelnewbies.org/KernelJanitors

  
  GIT, Fast Version Control System:
  	http://git-scm.com/