submittingdrivers

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Submitting Drivers For The Linux Kernel
---------------------------------------

This document is intended to explain how to submit device drivers to the
Linux 2.2 and 2.4 kernel trees. Note that if you are interested in video
card drivers you should probably talk to XFree86 (http://wwww.xfree86.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 better
known as H Peter Anvin). 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.

If you don't use assigned numbers then when you device is submitted it will
get 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:
	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 Alan Cox <[e-mail]>

Linux 2.4:
	This kernel tree is under active development. The same rules apply
	as 2.2 but you may wish to submit your driver via linux-kernel (see
	resources) and follow that list to track changes in API's. These
	should no longer be occuring as we are now in a code freeze.
	The final contact point for Linux 2.4 submissions is 	
	<[e-mail]>.

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 exclusively 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.

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 Documentation/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 seperate them out nicely and note
		this fact.

Portability:	Pointers are not always 32bits, 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.

Control:	In general if there is active maintainance 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.??.kernel.org:/pub/linux/kernel/...
	?? == your country code, such as "us", "uk", "fr", etc.

Linux kernel mailing list:		
	[e-mail]
	[mail [e-mail] to subscribe]

Kernel traffic:
	Weekly summary of kernel list activity (much easier to read)
	[http://kt.zork.net/kernel-traffic]

Linux USB project:
	http://sourceforge.net/projects/linux-usb/