[mirror_ubuntu-hirsute-kernel.git] / Documentation / 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:
	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 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 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/
Commit	Line	Data
1da177e4	1	Submitting Drivers For The Linux Kernel
ceeb1a54	2	=======================================
1da177e4 LT	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
84da7c08 RD	16	by the Linux assigned name and number authority (currently this is
84da7c08 RD	17	Torben Mathiasen). The site is http://www.lanana.org/. This
1da177e4 LT	18	also deals with allocating numbers for devices that are not going to
1da177e4 LT	19	be submitted to the mainstream kernel.
84da7c08	20	See Documentation/devices.txt for more information on this.
1da177e4	21
84da7c08 RD	22	If you don't use assigned numbers then when your device is submitted it will
84da7c08 RD	23	be given an assigned number even if that is different from values you may
1da177e4 LT	24	have shipped to customers before.
	25
	26	Who To Submit Drivers To
	27	------------------------
	28
	29	Linux 2.0:
5b0ed2c6	30	No new drivers are accepted for this kernel tree.
1da177e4 LT	31
1da177e4 LT	32	Linux 2.2:
5b0ed2c6 XVP	33	No new drivers are accepted for this kernel tree.
	34
	35	Linux 2.4:
1da177e4 LT	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
507a6a8c	39	maintainer then please contact Willy Tarreau <w@1wt.eu>.
1da177e4 LT	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
e1f8e874	44	submissions is Andrew Morton.
1da177e4 LT	45
	46	What Criteria Determine Acceptance
	47	----------------------------------
	48
ceeb1a54 MCC	49	Licensing:
ceeb1a54 MCC	50	The code must be released to us under the
1da177e4	51	GNU General Public License. We don't insist on any kind
84da7c08	52	of exclusive GPL licensing, and if you wish the driver
1da177e4 LT	53	to be useful to other communities such as BSD you may well
1da177e4 LT	54	wish to release under multiple licenses.
5b0ed2c6	55	See accepted licenses at include/linux/module.h
1da177e4	56
ceeb1a54 MCC	57	Copyright:
ceeb1a54 MCC	58	The copyright owner must agree to use of GPL.
1da177e4 LT	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
3706baa8	63	the copyright owner.
1da177e4	64
ceeb1a54 MCC	65	Interfaces:
ceeb1a54 MCC	66	If your driver uses existing interfaces and behaves like
1da177e4	67	other drivers in the same class it will be much more likely
3706baa8	68	to be accepted than if it invents gratuitous new ones.
1da177e4 LT	69	If you need to implement a common API over Linux and NT
	70	drivers do it in userspace.
	71
ceeb1a54 MCC	72	Code:
ceeb1a54 MCC	73	Please use the Linux style of code formatting as documented
1da177e4 LT	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
ceeb1a54 MCC	80	Portability:
ceeb1a54 MCC	81	Pointers are not always 32bits, not all computers are little
1da177e4 LT	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
ceeb1a54 MCC	89	Clarity:
ceeb1a54 MCC	90	It helps if anyone can see how to fix the driver. It helps
1da177e4 LT	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
ceeb1a54 MCC	95	PM support:
ceeb1a54 MCC	96	Since Linux is used on many portable and desktop systems, your
5b795202 RW	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
ceeb1a54 MCC	111	Control:
ceeb1a54 MCC	112	In general if there is active maintenance of a driver by
3706baa8	113	the author then patches will be redirected to them unless
1da177e4 LT	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
ceeb1a54 MCC	122	Vendor:
ceeb1a54 MCC	123	Being the hardware vendor and maintaining the driver is
1da177e4 LT	124	often a good thing. If there is a stable working driver from
1da177e4 LT	125	other people already in the tree don't expect 'we are the
3706baa8	126	vendor' to get your driver chosen. Ideally work with the
1da177e4 LT	127	existing driver author to build a single perfect driver.
1da177e4 LT	128
ceeb1a54 MCC	129	Author:
ceeb1a54 MCC	130	It doesn't matter if a large Linux company wrote the driver,
1da177e4 LT	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:
ceeb1a54 MCC	140	ftp.\ country_code\ .kernel.org:/pub/linux/kernel/...
	141
	142	where country_code == your country code, such as
	143	us, uk, fr, etc.
1da177e4	144
399e1d9c	145	http://git.kernel.org/?p=linux/kernel/git/torvalds/linux.git
6d06b81b	146
3706baa8	147	Linux kernel mailing list:
1da177e4 LT	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
1da177e4 LT	154	LWN.net:
1da177e4 LT	155	Weekly summary of kernel development activity - http://lwn.net/
ceeb1a54	156
1da177e4	157	2.6 API changes:
ceeb1a54	158
1da177e4	159	http://lwn.net/Articles/2.6-kernel-api/
ceeb1a54	160
1da177e4	161	Porting drivers from prior kernels to 2.6:
ceeb1a54	162
1da177e4 LT	163	http://lwn.net/Articles/driver-porting/
1da177e4 LT	164
1da177e4 LT	165	KernelNewbies:
1da177e4 LT	166	Documentation and assistance for new kernel programmers
ceeb1a54 MCC	167
ceeb1a54 MCC	168	http://kernelnewbies.org/
1da177e4 LT	169
1da177e4 LT	170	Linux USB project:
e1b114ee	171	http://www.linux-usb.org/
5b0ed2c6	172
3706baa8 AD	173	How to NOT write kernel driver by Arjan van de Ven:
3706baa8 AD	174	http://www.fenrus.org/how-to-not-write-a-device-driver-paper.pdf
5b0ed2c6 XVP	175
5b0ed2c6 XVP	176	Kernel Janitor:
0ea6e611	177	http://kernelnewbies.org/KernelJanitors
6d06b81b AA	178
	179	GIT, Fast Version Control System:
	180	http://git-scm.com/