[GitHub/mt8127/android_kernel_alcatel_ttab.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.??.kernel.org:/pub/linux/kernel/...
	?? == 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/

KernelTrap:
	Occasional Linux kernel articles and developer interviews
	http://kerneltrap.org/

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 LT	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
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
	49	Licensing: The code must be released to us under the
	50	GNU General Public License. We don't insist on any kind
84da7c08	51	of exclusive GPL licensing, and if you wish the driver
1da177e4 LT	52	to be useful to other communities such as BSD you may well
1da177e4 LT	53	wish to release under multiple licenses.
5b0ed2c6	54	See accepted licenses at include/linux/module.h
1da177e4 LT	55
	56	Copyright: The copyright owner must agree to use of GPL.
	57	It's best if the submitter and copyright owner
	58	are the same person/entity. If not, the name of
	59	the person/entity authorizing use of GPL should be
	60	listed in case it's necessary to verify the will of
3706baa8	61	the copyright owner.
1da177e4 LT	62
	63	Interfaces: If your driver uses existing interfaces and behaves like
	64	other drivers in the same class it will be much more likely
3706baa8	65	to be accepted than if it invents gratuitous new ones.
1da177e4 LT	66	If you need to implement a common API over Linux and NT
	67	drivers do it in userspace.
	68
	69	Code: Please use the Linux style of code formatting as documented
	70	in Documentation/CodingStyle. If you have sections of code
	71	that need to be in other formats, for example because they
	72	are shared with a windows driver kit and you want to
	73	maintain them just once separate them out nicely and note
	74	this fact.
	75
	76	Portability: Pointers are not always 32bits, not all computers are little
	77	endian, people do not all have floating point and you
	78	shouldn't use inline x86 assembler in your driver without
	79	careful thought. Pure x86 drivers generally are not popular.
	80	If you only have x86 hardware it is hard to test portability
	81	but it is easy to make sure the code can easily be made
	82	portable.
	83
	84	Clarity: It helps if anyone can see how to fix the driver. It helps
	85	you because you get patches not bug reports. If you submit a
	86	driver that intentionally obfuscates how the hardware works
	87	it will go in the bitbucket.
	88
5b795202 RW	89	PM support: Since Linux is used on many portable and desktop systems, your
	90	driver is likely to be used on such a system and therefore it
	91	should support basic power management by implementing, if
	92	necessary, the .suspend and .resume methods used during the
	93	system-wide suspend and resume transitions. You should verify
	94	that your driver correctly handles the suspend and resume, but
	95	if you are unable to ensure that, please at least define the
	96	.suspend method returning the -ENOSYS ("Function not
	97	implemented") error. You should also try to make sure that your
	98	driver uses as little power as possible when it's not doing
	99	anything. For the driver testing instructions see
	100	Documentation/power/drivers-testing.txt and for a relatively
	101	complete overview of the power management issues related to
	102	drivers see Documentation/power/devices.txt .
	103
25985edc	104	Control: In general if there is active maintenance of a driver by
3706baa8	105	the author then patches will be redirected to them unless
1da177e4 LT	106	they are totally obvious and without need of checking.
	107	If you want to be the contact and update point for the
	108	driver it is a good idea to state this in the comments,
	109	and include an entry in MAINTAINERS for your driver.
	110
	111	What Criteria Do Not Determine Acceptance
	112	-----------------------------------------
	113
	114	Vendor: Being the hardware vendor and maintaining the driver is
	115	often a good thing. If there is a stable working driver from
	116	other people already in the tree don't expect 'we are the
3706baa8	117	vendor' to get your driver chosen. Ideally work with the
1da177e4 LT	118	existing driver author to build a single perfect driver.
	119
	120	Author: It doesn't matter if a large Linux company wrote the driver,
	121	or you did. Nobody has any special access to the kernel
	122	tree. Anyone who tells you otherwise isn't telling the
	123	whole story.
	124
	125
	126	Resources
	127	---------
	128
	129	Linux kernel master tree:
	130	ftp.??.kernel.org:/pub/linux/kernel/...
	131	?? == your country code, such as "us", "uk", "fr", etc.
	132
399e1d9c	133	http://git.kernel.org/?p=linux/kernel/git/torvalds/linux.git
6d06b81b	134
3706baa8	135	Linux kernel mailing list:
1da177e4 LT	136	linux-kernel@vger.kernel.org
	137	[mail majordomo@vger.kernel.org to subscribe]
	138
	139	Linux Device Drivers, Third Edition (covers 2.6.10):
	140	http://lwn.net/Kernel/LDD3/ (free version)
	141
1da177e4 LT	142	LWN.net:
	143	Weekly summary of kernel development activity - http://lwn.net/
	144	2.6 API changes:
	145	http://lwn.net/Articles/2.6-kernel-api/
	146	Porting drivers from prior kernels to 2.6:
	147	http://lwn.net/Articles/driver-porting/
	148
	149	KernelTrap:
	150	Occasional Linux kernel articles and developer interviews
	151	http://kerneltrap.org/
	152
	153	KernelNewbies:
	154	Documentation and assistance for new kernel programmers
	155	http://kernelnewbies.org/
	156
	157	Linux USB project:
e1b114ee	158	http://www.linux-usb.org/
5b0ed2c6	159
3706baa8 AD	160	How to NOT write kernel driver by Arjan van de Ven:
3706baa8 AD	161	http://www.fenrus.org/how-to-not-write-a-device-driver-paper.pdf
5b0ed2c6 XVP	162
5b0ed2c6 XVP	163	Kernel Janitor:
0ea6e611	164	http://kernelnewbies.org/KernelJanitors
6d06b81b AA	165
	166	GIT, Fast Version Control System:
	167	http://git-scm.com/