[RFC] new uapi policy for drm

[Alex Deucher]

On Mon, Oct 14, 2019 at 2:16 PM Dave Airlie <airlied at gmail.com> wrote:
>
> I've kicked this around in my head over the past few weeks but wanted
> to get some feedback on whether it's a good idea or what impact it
> might have that I haven't considered.
>
> We are getting requests via both amdgpu/amdkfd and i915 for new user
> APIs for userspace drivers that throw code over the wall instead of
> being open source developed projects, but we are also seeing it for
> android drivers and kms properties, and we had that i915 crappy crtc
> background thing that was for Chrome but Chrome didn't want it.
>
> Now this presents a couple of issues:
>
> a) these projects don't seem to that good at following our development
> guidelines, avoid developing userspace features in parallel in the
> open and having good development implementations before submitting
> upstream.
>
> b) these projects don't have experienced userspace developers
> reviewing their kernel uapis. One big advantage of adding uapis with
> mesa developers is they have a lot of experience in the area as well.
>
> It's leading me to think I want to just stop all uapi submissions via
> driver trees, and instead mandate that all driver uapi changes are
> sent in separate git pull requests to dri-devel, I'd try (with some
> help) to catch all uapi modifications in normal trees, and refuse
> pulls that modified uapi.
>
> At least I'm considered writing the script and refusing and pulls that
> have a uapi change that doesn't contain a link to the userspace
> changes required for it in a public developed repo.
>
> Thoughts?

This seems like more hassle for questionable benefits.  I don't know
that mesa is really any better than any other driver teams with
respect to UAPI.  This just seems like sort of a arbitrary political
decision.  The people working on mesa have as much of an agenda as
those working on other projects.  Moreover, especially with the
migration to gitlab and MRs, I feel that mesa development has gotten
more opaque.  Say what you will about mailing lists, but at least you
could have a drive by view of what's going on.  With MRs, you sort of
have to seek out what to review; if stuff is not tagged with something
you feel is relevant, you probably won't look at it, so the only
people likely to review it are the people involved in writing it in
the first place, which would be the same whether it's mesa or some
other project.  I think all of the projects generally have the best
intentions at heart, but for better or worse they just have different
development models.  In the case of the AMD throw it over the wall
stuff, it's not really an anti-open source or community engagement
issue, it's more of how to we support several OSes, tons of new
products, several custom projects, etc. while leveraging as much
shared code as possible.  There are ways to make it work, but they are
usually a pretty heavy lift that not all teams can make.

All of that said, I think providing a link to the userspace user of
the API is reasonable, but I don't think there have been any egregious
cases of badly designed UAPI that were not caught using the existing
processes.

Alex