[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 Marcelo Tosatti
	<marcelo.tosatti@cyclades.com>.

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 <akpm@osdl.org>.

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 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:
	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://janitor.kernelnewbies.org/
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
5b0ed2c6 XVP	39	maintainer then please contact Marcelo Tosatti
5b0ed2c6 XVP	40	<marcelo.tosatti@cyclades.com>.
1da177e4 LT	41
	42	Linux 2.6:
	43	The same rules apply as 2.4 except that you should follow linux-kernel
	44	to track changes in API's. The final contact point for Linux 2.6
	45	submissions is Andrew Morton <akpm@osdl.org>.
	46
	47	What Criteria Determine Acceptance
	48	----------------------------------
	49
	50	Licensing: The code must be released to us under the
	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 LT	56
	57	Copyright: The copyright owner must agree to use of GPL.
	58	It's best if the submitter and copyright owner
	59	are the same person/entity. If not, the name of
	60	the person/entity authorizing use of GPL should be
	61	listed in case it's necessary to verify the will of
3706baa8	62	the copyright owner.
1da177e4 LT	63
	64	Interfaces: If your driver uses existing interfaces and behaves like
	65	other drivers in the same class it will be much more likely
3706baa8	66	to be accepted than if it invents gratuitous new ones.
1da177e4 LT	67	If you need to implement a common API over Linux and NT
	68	drivers do it in userspace.
	69
	70	Code: Please use the Linux style of code formatting as documented
	71	in Documentation/CodingStyle. If you have sections of code
	72	that need to be in other formats, for example because they
	73	are shared with a windows driver kit and you want to
	74	maintain them just once separate them out nicely and note
	75	this fact.
	76
	77	Portability: Pointers are not always 32bits, not all computers are little
	78	endian, people do not all have floating point and you
	79	shouldn't use inline x86 assembler in your driver without
	80	careful thought. Pure x86 drivers generally are not popular.
	81	If you only have x86 hardware it is hard to test portability
	82	but it is easy to make sure the code can easily be made
	83	portable.
	84
	85	Clarity: It helps if anyone can see how to fix the driver. It helps
	86	you because you get patches not bug reports. If you submit a
	87	driver that intentionally obfuscates how the hardware works
	88	it will go in the bitbucket.
	89
5b795202 RW	90	PM support: Since Linux is used on many portable and desktop systems, your
	91	driver is likely to be used on such a system and therefore it
	92	should support basic power management by implementing, if
	93	necessary, the .suspend and .resume methods used during the
	94	system-wide suspend and resume transitions. You should verify
	95	that your driver correctly handles the suspend and resume, but
	96	if you are unable to ensure that, please at least define the
	97	.suspend method returning the -ENOSYS ("Function not
	98	implemented") error. You should also try to make sure that your
	99	driver uses as little power as possible when it's not doing
	100	anything. For the driver testing instructions see
	101	Documentation/power/drivers-testing.txt and for a relatively
	102	complete overview of the power management issues related to
	103	drivers see Documentation/power/devices.txt .
	104
1da177e4	105	Control: In general if there is active maintainance of a driver by
3706baa8	106	the author then patches will be redirected to them unless
1da177e4 LT	107	they are totally obvious and without need of checking.
	108	If you want to be the contact and update point for the
	109	driver it is a good idea to state this in the comments,
	110	and include an entry in MAINTAINERS for your driver.
	111
	112	What Criteria Do Not Determine Acceptance
	113	-----------------------------------------
	114
	115	Vendor: Being the hardware vendor and maintaining the driver is
	116	often a good thing. If there is a stable working driver from
	117	other people already in the tree don't expect 'we are the
3706baa8	118	vendor' to get your driver chosen. Ideally work with the
1da177e4 LT	119	existing driver author to build a single perfect driver.
	120
	121	Author: It doesn't matter if a large Linux company wrote the driver,
	122	or you did. Nobody has any special access to the kernel
	123	tree. Anyone who tells you otherwise isn't telling the
	124	whole story.
	125
	126
	127	Resources
	128	---------
	129
	130	Linux kernel master tree:
	131	ftp.??.kernel.org:/pub/linux/kernel/...
	132	?? == your country code, such as "us", "uk", "fr", etc.
	133
3706baa8	134	Linux kernel mailing list:
1da177e4 LT	135	linux-kernel@vger.kernel.org
	136	[mail majordomo@vger.kernel.org to subscribe]
	137
	138	Linux Device Drivers, Third Edition (covers 2.6.10):
	139	http://lwn.net/Kernel/LDD3/ (free version)
	140
1da177e4 LT	141	LWN.net:
	142	Weekly summary of kernel development activity - http://lwn.net/
	143	2.6 API changes:
	144	http://lwn.net/Articles/2.6-kernel-api/
	145	Porting drivers from prior kernels to 2.6:
	146	http://lwn.net/Articles/driver-porting/
	147
	148	KernelTrap:
	149	Occasional Linux kernel articles and developer interviews
	150	http://kerneltrap.org/
	151
	152	KernelNewbies:
	153	Documentation and assistance for new kernel programmers
	154	http://kernelnewbies.org/
	155
	156	Linux USB project:
e1b114ee	157	http://www.linux-usb.org/
5b0ed2c6	158
3706baa8 AD	159	How to NOT write kernel driver by Arjan van de Ven:
3706baa8 AD	160	http://www.fenrus.org/how-to-not-write-a-device-driver-paper.pdf
5b0ed2c6 XVP	161
	162	Kernel Janitor:
	163	http://janitor.kernelnewbies.org/