Hello everyone,
As I've been working on the integration of the latest developments and fixes from upstream into the linaro-2.6.38 kernel lately, it became quickly evident that major merge conflicts were to be expected. The problem stems from the fact that we opened the 2.6.38 branch early i.e. around the 2.6.38-rc5 kernel. Many patches that were merged into the Linaro kernel have been subsequently modified by their respective maintainers until they were merged upstream, meaning that what we have now in mainline is different from what the Linaro kernel tree has. This creates several issues:
- It is hard to verify that what is in the Linaro tree is actually the latest and the best version of a patch.
- Merging additional fixes from upstream often ends up in merge conflicts requiring manual resolution, sometimes non-trivial ones, which is in itself a bug hazard.
- People wanting to contribute patches to the Linaro kernel potentially have to create a different patch than what they would submit upstream.
Given those issues, I decided to rebuild the linaro-2.6.38 branch from scratch to see where that would bring me. And as could be expected, the result looks nicer and it is much easier to work with than the current tree. For example, this allowed me to merge the latest OMAP support from mainline as is, including the latest fixes, without any need for backport work nor major conflict resolution. Another advantage is that the commit SHA1 references are now identical in most cases to what can be found into mainline.
So... my question is: should we switch to this rebuilt tree or not? There are drawbacks with such a move of course:
- All the testing done so far would be void. This is however not as bad as this may look as the rebuilt kernel contains fixes for existing bugs in the current tree, and the rebuilt kernel is using patches that have and still are being tested by a wider community.
- I didn't forward port a couple series of patches that are available in the current Linaro tree and not in mainline yet, including: * DT support (Grant Likely) * DVFS and PM for OMAP (Vishwanath Sripathy, Vishwanath BS) * Some ux500 fixups (Linus Walleij) * clock debug information (Yong Shen) * Samsung CPUIDLE (Amit Kachhap) So I would prefer if the people responsible for those patches did resubmit their patches once they apply to the new tree (that should be even easier now to apply patches that were meant for mainline).
- The history of the rebuilt tree is obviously different from the current tree's. This means special care when updating to the new tree with Git.
But overall I think there are more advantages than disadvantages for such a move. What other people think?
The current rebuilt tree can be seen at:
http://git.linaro.org/gitweb?p=kernel/linux-linaro-2.6.38.git%3Ba=shortlog%3...
or obtained from:
git://git.linaro.org/kernel/linux-linaro-2.6.38.git (the "rebuilt" branch)
Nicolas