Contributing to the kernel video drivers

[Warren Block]

On Mon, 28 Dec 2015, Jean-Sébastien Pédron wrote:

> I believe the milestones should be versions of Linux. For instance, the
> next one on the road is Linux 3.9. We have DRM core and two drivers to
> sync and I think we should try to keep the whole DRM in sync (and not
> have i915 at 3.15 and Radeon at 3.13 for instance). Until now, I updated
> our DRM on a file-by-file basis: I took a file from Linux 3.8 and ported
> it to FreeBSD from scratch, by keeping an eye on the current FreeBSD
> copy. Therefore, I jumped from whatever version we were at straight to
> 3.8, at the high cost of an unbuildable kernel before the very end.
>
> Another approach is to update on a commit-by-commit basis: we take all
> commits between 3.8 and 3.9 and apply them in order. The downside is
> that we could port code which is rewritten or removed 10 commits later.

This commit-by-commit approach is how FreeBSD documentation translation 
has been traditionally done.  There are a couple of problems with it 
beyond just wasted work.

It makes prioritizing important patches difficult.  Consider a patch to 
fix some really important bug that is needed now.  It can still be done 
now even if there are 100 upstream commits in front of it, but will make 
tracking and patching more difficult until those 100 commits are caught 
up.

Tracking by upstream commits also implies that most updates will be the 
same scale as the upstream commits.  A single massive upstream commit 
can put a hold on the process until it is completely ported.