[PATCH] gpu/docs: Clarify what userspace means for gl

Wed Apr 24 14:28:19 UTC 2019

On Wed, Apr 24, 2019 at 4:24 PM Zhou, David(ChunMing)
<David1.Zhou at amd.com> wrote:
> Will linux be only mesa-linux? I thought linux is an  open linux.
> Which will impact our opengl/amdvlk(MIT open source), not sure Rocm:
> 1. how to deal with one uapi that opengl/amdvlk needs but mesa dont need? reject?
> 2. one hw feature that opengl/amdvlk developers work on that but no mesa developers work on, cannot upstream as well?
>
> I think above two would easily happen, because there are many employees working on company project with many customer kinds of reqiurements, but mesa not.

Well those are the questions I tried to have a clear answer for, to
avoid confusion, but looks like the agreement isn't perfect. But
there's pretty clear favour towards cross vendor userspace that's
collaboratively and openly developed like mesa. So whenever one of the
above cases you bring up happen we'll get to have a big thread on
dri-devel I guess.
-Daniel


> -David
>
> -------- Original Message --------
> Subject: [PATCH] gpu/docs: Clarify what userspace means for gl
> From: Daniel Vetter
> To: DRI Development ,Mesa Dev
> CC: Jérôme Glisse ,Daniel Vetter ,Karol Herbst ,Kenneth Graunke ,Ben Skeggs ,Daniel Vetter ,Sean Paul
>
> Clear rules avoid arguing.
>
> Note that this just aims to document current expectations. If that
> shifts (e.g. because gl isn't the main api anymore, replaced by vk),
> then we need to update this text.
>
> I think it'd be good to have an equally solid list on the kms side.
> But kms is much more meant to be a standard, and the list of userspace
> projects we've accepted in the past is constantly shifting and
> adjusting. So I figured I'll leave that as an exercise for later on.
>
> v2: Try to clarify that we don't want a mesa driver just for mesa's
> sake, and more clearly exclude anything that just doesn't make sense
> technically.  Example would be a compute driver that makes sense to be
> merged into drm (for kernel side code-sharing), but where the intended
> use is some single-source CUDA-style compute without ever bothering
> about any of the 3D/rendering side baggage that comes with gl/vk.
>
> v3: Drop vulkan for now, the situation there isn't as obviously
> clear-cut as on the gl side, and I don't want to tank this idea on a
> hot discussion about vk and mesa. Plus I think once we have 1-2 more
> vk drivers in mesa the situation on the vk side is clear-cut too, and
> we can do a follow-up patch to add vk to the list where we expect the
> userspace to be in upstream mesa. That's would give nice precedence to
> make it clear that this isn't cast in stone, but meant to reflect
> reality and should be adjusted as needed.
>
> v4: Fix typo.
>
> v5: Add a note to the commit message that this text needs to be
> updated when the situation changes.
>
> v6: Add a sentence why mesa will give the most meaningful review on gl
> stuff - it's a very active project with lots of developers.
>
> Acked-by: Dave Airlie <airlied at gmail.com> (v4)
> Acked-by: Eric Anholt <eric at anholt.net> (v4)
> Acked-by: Alex Deucher <alexdeucher at gmail.com> (v5)
> Acked-by: Sean Paul <sean at poorly.run> (v5)
> Acked-by: Kenneth Graunke <kenneth at whitecape.org> (v5)
> Acked-by: Karol Herbst <karolherbst at gmail.com> (v5)
> Acked-by: Rob Clark <robdclark at gmail.com>
> Acked-by: Jérôme Glisse <jglisse at redhat.com>
> Acked-by: Bas Nieuwenhuizen <bas at basnieuwenhuizen.nl>
> Acked-by: Ben Skeggs <skeggs at redhat.com>
> Cc: Dave Airlie <airlied at gmail.com>
> Cc: Eric Anholt <eric at anholt.net>
> Cc: Alex Deucher <alexdeucher at gmail.com>
> Cc: Sean Paul <sean at poorly.run>
> Cc: Kenneth Graunke <kenneth at whitecape.org>
> Cc: Karol Herbst <karolherbst at gmail.com>
> Cc: Rob Clark <robdclark at gmail.com>
> Cc: Jérôme Glisse <jglisse at redhat.com>
> Cc: Bas Nieuwenhuizen <bas at basnieuwenhuizen.nl>
> Cc: Ben Skeggs <skeggs at redhat.com>
> Signed-off-by: Daniel Vetter <daniel.vetter at intel.com>
> ---
> I chatted with a pile of people in private, and there's clearly some
> solid support for this. But there's also some big concerns brought up
> by other people. The main one summed up is "what if everyone just
> ships vk, with a generic gl-on-vk like ANGLE?", but there's other
> concerns too.
>
> So all together I think this doesn't clear the bar of (almost)
> unanimous support which we need to make documentation actually help
> with clarifying what's expected. And if/when someone comes up with a
> more creative userspace approach for gl/vk we'll need to figure this
> all out with the time honored tradition of having a few massive
> threads on dri-devel :-)
>
> Hence this is more fyi as a guidance I guess, not a strict&hard rule.
> And I don't plan on merging this.
>
> Cheers, Daniel
> ---
>  Documentation/gpu/drm-uapi.rst | 25 +++++++++++++++++++++++++
>  1 file changed, 25 insertions(+)
>
> diff --git a/Documentation/gpu/drm-uapi.rst b/Documentation/gpu/drm-uapi.rst
> index c9fd23efd957..0f767cfd5db6 100644
> --- a/Documentation/gpu/drm-uapi.rst
> +++ b/Documentation/gpu/drm-uapi.rst
> @@ -105,6 +105,31 @@ is already rather painful for the DRM subsystem, with multiple different uAPIs
>  for the same thing co-existing. If we add a few more complete mistakes into the
>  mix every year it would be entirely unmanageable.
>
> +Below some clarifications what this means for specific areas in DRM.
> +
> +Compute&Rendering Userspace
> +---------------------------
> +
> +Userspace API for enabling compute and rendering blocks which are capable of at
> +least supporting one of the OpenGL or OpenGL ES standards from Khronos need to
> +be enabled in the upstream `Mesa3D project<https://www.mesa3d.org/>`.
> +
> +Mesa3D is the canonical upstream for these areas because it is a fully
> +compliant, performant and cross-vendor implementation that supports all kernel
> +drivers in DRM. It is also an active project with plenty of developers who
> +can perform meaningful review. It is therefore the best platform to validate
> +userspace API and especially make sure that cross-vendor interoperation is
> +assured.
> +
> +Other userspace is only admissible if exposing a given feature through OpenGL or
> +OpenGL ES would result in a technically unsound design, incomplete driver or
> +an implementation which isn't useful in real world usage.
> +
> +Other areas, like media codec, which Mesa3D supports for just some drivers, but
> +isn't the clear universal choice, are excluded from this policy. Driver teams
> +are still encourage to aim for shared, cross-vendor infrastructure in userspace
> +as much as possible.
> +
>  .. _drm_render_node:
>
>  Render nodes
> --
> 2.20.1
>
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch