[Mesa-dev] Help! CopyImageSubData is defeating me

[Jason Ekstrand]

On June 25, 2017 2:31:56 PM Ilia Mirkin <imirkin at alum.mit.edu> wrote:

> On Sun, Jun 25, 2017 at 5:25 PM, Jason Ekstrand <jason at jlekstrand.net> wrote:
>> On June 25, 2017 1:40:09 PM Ilia Mirkin <imirkin at alum.mit.edu> wrote:
>>
>>> On Sun, Jun 25, 2017 at 4:33 PM, Jason Ekstrand <jason at jlekstrand.net>
>>> wrote:
>>>>>
>>>>> Anyone have thoughts on this? Am I being foolish for trying to hold
>>>>> onto GL_RGBA4 texturing? (Any decision here also affects st/nine.)
>>>>
>>>>
>>>>
>>>> Yes.  Chances are that you're also doing texture views wrong.  Are there
>>>> any
>>>> 4444 formats supported on nvidia hardware?
>>>
>>>
>>> Well, any permutation of a 4444 format is easily supportable for
>>> texturing.
>>>
>>> What's wrong with the texture views? Should be fine... unless I'm
>>> missing something. It's really just this issue with RB <-> Texture
>>> copies where the RB's internal format is GL_RGBA4 while the *real*
>>> internal format is RGBA8. Texture views between e.g. RGB565 and
>>> RGBA4444 should work fine (and the fb will fail to validate as one
>>> might expect if one were to attach a GL_RGBA4 texture view of a
>>> GL_RGB565 texture).
>>
>>
>> But what if you have a 4444 and you render to as 4444 and then try to
>> texture from it as 565?
>
> If you have a 4444 texture and attach it to a FB, then that FB will
> not be complete. So you can't render to it in the first place.

Ok, then I'm confused as to how you have a copy_image problem.  Is the 
issue just that gallium won't let you CopyImageSubData into a texture you 
can't render into?  Why not just treat it as R16 when using it as a 
copy_image destination?