[Mesa-dev] [PATCH 2/2] mesa/st: add ARB_texture_view support

[Jose Fonseca]

On 20/08/14 17:14, Roland Scheidegger wrote:
> Am 20.08.2014 17:55, schrieb Ilia Mirkin:
>> On Wed, Aug 20, 2014 at 11:47 AM, Jose Fonseca <jfonseca at vmware.com> wrote:
>>> On 20/08/14 16:31, Ilia Mirkin wrote:
>>>>
>>>> Hm, it's not tested. And you're right, that would (most likely) mess
>>>> up, since it would only have the pipe_resource's target. Any
>>>> suggestions on how to fix it? Should the target be added to
>>>> pipe_sampler_view?
>>>>
>>>> On Wed, Aug 20, 2014 at 11:25 AM, Roland Scheidegger <sroland at vmware.com>
>>>> wrote:
>>>>>
>>>>> Didn't look at it that closely, but I'm pretty surprised this really
>>>>> works. One things ARB_texture_view can do is cast cube maps (and cube
>>>>> map arrays) to 2d arrays and vice versa (also 1d/2d to the respective
>>>>> array type), and we cannot express that in sampler views (yet) (we can't
>>>>> express it in surfaces neither but there it should not matter). Which
>>>>> means the type used in the shader for sampling will not match the
>>>>> sampler view, which sounds quite broken to me.
>>>>>
>>>>> Roland
>>>>>
>>>
>>> Probably the only sane thing to do eliminate the disctinction between
>>> PIPE_TEXTURE_FOO and PIPE_TEXTURE_FOO_ARRAY like  in
>>> https://urldefense.proofpoint.com/v1/url?u=http://msdn.microsoft.com/en-us/library/windows/desktop/ff476202.aspx&k=oIvRg1%2BdGAgOoM1BIlLLqw%3D%3D%0A&r=F4msKE2WxRzA%2BwN%2B25muztFm5TSPwE8HKJfWfR2NgfY%3D%0A&m=x03OmuVWAQgfFbsFB2SLMLwSYavxkU8Zsypu9lEIkpg%3D%0A&s=4b0ca75d91e6d53d92658d9e334cf2a73a01efe5667464c969f5c085409052ff ,
>>> e.g.,:
>>>
>>> enum pipe_texture_target {
>>>     PIPE_BUFFER           = 0,
>>>     PIPE_TEXTURE_1D       = 1,
>>>     PIPE_TEXTURE_2D       = 2,
>>>     PIPE_TEXTURE_3D       = 3,
>>>     PIPE_TEXTURE_CUBE     = 4, // Must have same layout as PIPE_TEXTURE_2D
>>>     PIPE_TEXTURE_RECT     = 5,
>>>     PIPE_TEXTURE_1D_ARRAY = PIPE_TEXTURE_1D,
>>>     PIPE_TEXTURE_2D_ARRAY = PIPE_TEXTURE_2D,
>>>     PIPE_TEXTURE_CUBE_ARRAY = PIPE_TEXTURE_CUBE,
>>>     PIPE_MAX_TEXTURE_TYPES
>>> };
>>>
>>>
>>> We could also remove PIPE_TEXTURE_CUBE and have cube-maps be PIPE_TEXTURE_2D
>>> with a flag, but that's probably a lot of work. Instead, drivers that want
>>> to be able to support ARB_texture_view will need to ensure
>>> PIPE_TEXTURE_CUBE/PIPE_TEXTURE_2D layout match.
>>
>> Another quick + cheap alternative (at least looking at nv50/nvc0 code)
>> would be to pass a separate target parameter to
>> ->create_sampler_view(). That would be enough for nouveau, but perhaps
>> not more generally? Take a look at nv50_tex.c:nv50_create_texture_view
>> -- it also needs to work out the depth of the texture (presumably to
>> deal with out-of-bounds accesses) and that is written to the texture
>> info structure.
> Well that should be enough, but I don't think it fits out design.


 > We've
> encapsulated other "override" information like the format in the view
> already, and I see no reason why the target "cast" should be treated any
> different.

In other words, you're arguing for:

diff --git a/src/gallium/include/pipe/p_state.h 
b/src/gallium/include/pipe/p_state.h
index a82686b..c87ac4e 100644
--- a/src/gallium/include/pipe/p_state.h
+++ b/src/gallium/include/pipe/p_state.h
@@ -333,6 +333,7 @@ struct pipe_surface
     struct pipe_reference reference;
     struct pipe_resource *texture; /**< resource into which this is a 
view  */
     struct pipe_context *context; /**< context this surface belongs to */
+   enum pipe_texture target;
     enum pipe_format format;

     /* XXX width/height should be removed */


It's a fair point.  And I don't object that solution.

Of course, for this to work, drivers will need to treat the _ARRAY and 
non _ARRAY targets the same when determining the texture layout for this 
to work.


I just felt this would be a good oportunity to slim down 
pipe_texture_target too.  I'm not sure the _ARRAY distinction still 
matters at this level, but I suppose it doesn't hurt.


Jose