Linux Kernel Architecture

Mauerer runbapp06.tex V1 - 09/04/2008 6:14pm Page 1279

Appendix F: The Kernel Development Process

Origin of Patches

The description also contains asigned-offline, which identifies who wrote the patch, and serves as a bona

fide statement that the author has the right to publish the code as open source, usually covered by the

GNU General Public License (GPL), version 2.

Multiple persons can sign off a patch, even if they are not direct authors of the code. This signals that

the signer has reviewed the patch, is intimately acquainted with the code, and believes to the best of his

knowledge that it will work as announced and not cause data corruption, set your laptop on fire, or do

other nasty things. It also tracks the path a patch has made through the developer hierarchy before it

finally ended up in the vanilla kernel. Maintainers are heavily involved in signing off, because they have

to review a fair amount of code that they have not written themselves for inclusion in their subsystems.

Only real names will be accepted for signed-off-lines — pseudonyms and fictitious names must not be

used. Formally, signing off a patch means that the signer can certify the following:

Documentation/SubmittingPatches

Developer’s Certificate of Origin 1.1

By making a contribution to this project, I certify that:

(a) The contribution was created in whole or in part by me and I

have the right to submit it under the open source license

indicated in the file; or

(b) The contribution is based upon previous work that, to the best

of my knowledge, is covered under an appropriate open source

license and I have the right under that license to submit that

work with modifications, whether created in whole or in part

by me, under the same open source license (unless I am

permitted to submit under a different license), as indicated

in the file; or

(c) The contribution was provided directly to me by some other

person who certified (a), (b) or (c) and I have not modified

it.

(d) I understand and agree that this project and the contribution

are public and that a record of the contribution (including all

personal information I submit with it, including my sign-off) is

maintained indefinitely and may be redistributed consistent with

this project or the open source license(s) involved.

Signing patches off was introduced to kernel development at a rather late stage, essentially as a reaction

to a claim by a ‘‘three-letter company’’ that for various reasons assumed the impression that they would

own all the code of the kernel, and therefore all Linux users should give them all their money. Naturally,

some developers did not quite agree with this point of view, including Linus Torvalds himself:^4

Some of you may have heard of this crazy company called SCO (aka "Smoking

Crack Organization") who seem to have a hard time believing that open

(^4) Accusing people of smoking crack is, by the way, not completely uncommon on the Linux kernel mailing list, where conversations
can sometimes be rough.