[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 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 <alan@lxorguk.ukuu.org.uk>

Linux 2.4:
	The same rules apply as 2.2. The final contact point for Linux 2.4
	submissions is 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 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.

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 copright 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.

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)

Kernel traffic:
	Weekly summary of kernel list activity (much easier to read)
	http://www.kerneltraffic.org/kernel-traffic/

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://sourceforge.net/projects/linux-usb/
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
	16	by the Linux assigned name and number authority (currently better
	17	known as H Peter Anvin). The site is http://www.lanana.org/. This
	18	also deals with allocating numbers for devices that are not going to
	19	be submitted to the mainstream kernel.
	20
	21	If you don't use assigned numbers then when you device is submitted it will
	22	get given an assigned number even if that is different from values you may
	23	have shipped to customers before.
	24
	25	Who To Submit Drivers To
	26	------------------------
	27
	28	Linux 2.0:
	29	No new drivers are accepted for this kernel tree
	30
	31	Linux 2.2:
	32	If the code area has a general maintainer then please submit it to
	33	the maintainer listed in MAINTAINERS in the kernel file. If the
	34	maintainer does not respond or you cannot find the appropriate
	35	maintainer then please contact Alan Cox <alan@lxorguk.ukuu.org.uk>
	36
	37	Linux 2.4:
	38	The same rules apply as 2.2. The final contact point for Linux 2.4
	39	submissions is Marcelo Tosatti <marcelo.tosatti@cyclades.com>.
	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
	44	submissions is Andrew Morton <akpm@osdl.org>.
	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
	51	of exclusively GPL licensing, and if you wish the driver
	52	to be useful to other communities such as BSD you may well
	53	wish to release under multiple licenses.
	54
	55	Copyright: The copyright owner must agree to use of GPL.
	56	It's best if the submitter and copyright owner
	57	are the same person/entity. If not, the name of
	58	the person/entity authorizing use of GPL should be
	59	listed in case it's necessary to verify the will of
	60	the copright owner.
	61
	62	Interfaces: If your driver uses existing interfaces and behaves like
	63	other drivers in the same class it will be much more likely
	64	to be accepted than if it invents gratuitous new ones.
65	If you need to implement a common API over Linux and NT
66	drivers do it in userspace.
67
68	Code: Please use the Linux style of code formatting as documented
69	in Documentation/CodingStyle. If you have sections of code
70	that need to be in other formats, for example because they
71	are shared with a windows driver kit and you want to
72	maintain them just once separate them out nicely and note
73	this fact.
74
75	Portability: Pointers are not always 32bits, not all computers are little
76	endian, people do not all have floating point and you
77	shouldn't use inline x86 assembler in your driver without
78	careful thought. Pure x86 drivers generally are not popular.
79	If you only have x86 hardware it is hard to test portability
80	but it is easy to make sure the code can easily be made
81	portable.
82
83	Clarity: It helps if anyone can see how to fix the driver. It helps
84	you because you get patches not bug reports. If you submit a
85	driver that intentionally obfuscates how the hardware works
86	it will go in the bitbucket.
87
88	Control: In general if there is active maintainance of a driver by
89	the author then patches will be redirected to them unless
90	they are totally obvious and without need of checking.
91	If you want to be the contact and update point for the
92	driver it is a good idea to state this in the comments,
93	and include an entry in MAINTAINERS for your driver.
94
95	What Criteria Do Not Determine Acceptance
96	-----------------------------------------
97
98	Vendor: Being the hardware vendor and maintaining the driver is
99	often a good thing. If there is a stable working driver from
100	other people already in the tree don't expect 'we are the
101	vendor' to get your driver chosen. Ideally work with the
102	existing driver author to build a single perfect driver.
103
104	Author: It doesn't matter if a large Linux company wrote the driver,
105	or you did. Nobody has any special access to the kernel
106	tree. Anyone who tells you otherwise isn't telling the
107	whole story.
108
109
110	Resources
111	---------
112
113	Linux kernel master tree:
114	ftp.??.kernel.org:/pub/linux/kernel/...
115	?? == your country code, such as "us", "uk", "fr", etc.
116
117	Linux kernel mailing list:
118	linux-kernel@vger.kernel.org
119	[mail majordomo@vger.kernel.org to subscribe]
120
121	Linux Device Drivers, Third Edition (covers 2.6.10):
122	http://lwn.net/Kernel/LDD3/ (free version)
123
124	Kernel traffic:
125	Weekly summary of kernel list activity (much easier to read)
126	http://www.kerneltraffic.org/kernel-traffic/
127
128	LWN.net:
129	Weekly summary of kernel development activity - http://lwn.net/
130	2.6 API changes:
131	http://lwn.net/Articles/2.6-kernel-api/
132	Porting drivers from prior kernels to 2.6:
133	http://lwn.net/Articles/driver-porting/
134
135	KernelTrap:
136	Occasional Linux kernel articles and developer interviews
137	http://kerneltrap.org/
138
139	KernelNewbies:
140	Documentation and assistance for new kernel programmers
141	http://kernelnewbies.org/
142
143	Linux USB project:
144	http://sourceforge.net/projects/linux-usb/
145