[Mesa-dev] [android-x86-devel] Re: gralloc_drm_pipe

[Rob Clark]

On Sun, Mar 6, 2016 at 9:29 PM, Chih-Wei Huang <cwhuang at android-x86.org> wrote:
> 2016-03-05 3:53 GMT+08:00 Rob Clark <robdclark at gmail.com>:
>> On Fri, Mar 4, 2016 at 2:43 PM, Thomas Hellstrom <thellstrom at vmware.com> wrote:
>>> On 03/04/2016 07:07 PM, Rob Clark wrote:
>>>> On Fri, Mar 4, 2016 at 12:59 PM, Rob Clark <robdclark at gmail.com> wrote:
>>>>> So, I've been advocating that for android, gallium drivers use
>>>>> gralloc_drm_pipe, since with android it seems like you end up with
>>>>> both gralloc and libGL in the same process, and having both share the
>>>>> same pipe_screen avoids lots of headaches with multiple gem handles
>>>>> pointing to same underlying buffer.
>>>>>
>>>>> But the awkward thing is that gralloc_drm_pipe is using gallium APIs
>>>>> that aren't particularly intended to be used out-of-tree.  Ie. not
>>>>> really stable APIs.  At the time, the thing that made sense to me was
>>>>> to pull drm_gralloc into mesa.  But at the time, there were no
>>>>> non-mesa users of drm_gralloc, which isn't really true anymore.
>>>>>
>>>>> Maybe what makes more sense now is to implement a gralloc state
>>>>> tracker, which exposes a stable API for drm_gralloc?  It would mostly
>>>>> be a shim to expose gallium import/export/transfer APIs in a stable
>>>>> way, but would also be where the code that figures out which driver to
>>>>> use to create/get the pipe_screen.
>>>> and actually, we might just be able to use XA state tracker for this..
>>>> I think it exposes all the necessary import/export/etc stuff that
>>>> gralloc would need..
>>>>
>>>> BR,
>>>> -R
>>>>
>>> and it was created for a very similar purpose, except that we also
>>> needed some
>>> render functionality, enough to composite surfaces.
>>
>> right, and since we have the ability to import/export dmabuf handles,
>> I think it is a superset of what is needed.  (gralloc is using blits
>> instead of flips for vmwgfx, for reasons I don't fully understand..
>> but XA can do these blits and more, so we are still good there)
>
> Hi Rob,
> Thank you for raising the problem though
> I don't fully understand the technical details.
>
> So you are planning to modify (or re-implement?)
> gralloc_drm_pipe to use the APIs of XA state tracker.

well, unless I can talk someone else into doing it before I find time ;-)

But yeah, if no one else does it (or comes up with a better idea
first), I will eventually do it.

fwiw, the XA API is:

https://cgit.freedesktop.org/mesa/mesa/tree/src/gallium/state_trackers/xa/xa_tracker.h
https://cgit.freedesktop.org/mesa/mesa/tree/src/gallium/state_trackers/xa/xa_context.h
(ignoring the composite bits which we shouldn't need)

I think that should provide everything needed for gralloc, but with a
stable API rather than using the gallium pipe screen/context APIs
directly.

BR,
-R

> Do I understand your words correctly?
>