Subversion Repositories or1k_soc_on_altera_embedded_dev_kit

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 .

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 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/