[Mesa-dev] Moving amdgpu/addrlib into a git submodule

[Rob Clark]

On Tue, Aug 9, 2016 at 9:47 AM, Nicolai Hähnle <nhaehnle at gmail.com> wrote:
> Hi everybody,
>
> addrlib is the addressing and alignment calculator which is used by
> radeonsi. It's developed (and also used) internally at AMD, and so far we've
> had one open source copy living in the Mesa repository at
> src/gallium/winsys/amdgpu/drm/addrlib.
>
> The question of using addrlib in non-Mesa parts of our open-source stack has
> come up, in particular in relation to compute. We'd obviously like to share
> the code rather than having multiple copies flying around. Since the
> interface of addrlib is slow-moving but unstable, shared linking is not an
> option.
>
> I think the best way forward is to create a dedicated repository for addrlib
> which is then integrated into Mesa as a git submodule.
>
> The point of this email is to gather feedback from the Mesa community on
> this plan, which is explicitly:
>
> (0) Create an addrlib repository, say amd/addrlib on fd.o.
> (1) Add it as a git submodule to the Mesa repository.
> (2) Fix up whatever aspects of the build system that may be affected
> (perhaps for building source tarballs).
> (3) Go back to mostly ignoring addrlib, except for trying to get better at
> syncing with the internal closed-source version.
>
> From initial experiments, the impact on users interested in radeon is that
> they will have to run `git submodule init` and then occasionally `git
> submodule update`. Users who do not build radeonsi should be able to ignore
> the change completely.

tbh, git submodules are more annoying than they need to be, and I'm
not really terribly excited to use that for something that is a build
dependency.  Maybe just move it into libdrm instead?

BR,
-R

> There are alternatives. For example, ROCm uses Google's repo tool already.
> But for Mesa, git submodule looks like a lightweight, well supported and
> overall conservative option that everybody should already have installed. If
> there are good arguments for something else, let's hear them!
>
> Another point: if we proceed with this plan, I think we should consider
> moving addrlib into src/amd/addrlib. There are two reasons: First,
> transitioning to a submodule *without* changing the directory is probably
> more fragile, i.e. what happens when you switch between checkouts before and
> after the transition. Second, if/when radv ends up being merged into Mesa
> master, it makes sense to have addrlib there anyway.
>
> Thoughts? Complaints? Praise?
> Nicolai
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