docs/gallium: Note samplers are not used for txf

Now that PIPE_CAP_TEXTURE_BUFFER_SAMPLER is gone, txf does not require samplers
for any texture on any Gallium driver. NIR already requires drivers to ignore
sampler_index for non-sampler operation (mainly txf), and nowadays all Gallium
drivers ingest NIR. So, document that samplers aren't bound for txf (etc) as
part of the Gallium frontend-driver contract.

Signed-off-by: Alyssa Rosenzweig <alyssa@collabora.com>
Suggested-by: Marek Olšák <marek.olsak@amd.com>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/22223>

diff --git a/docs/gallium/context.rst b/docs/gallium/context.rst
index a3fd78b..507a6c0 100644 (file)
--- a/docs/gallium/context.rst
+++ b/docs/gallium/context.rst
@@ -128,11 +128,12 @@ objects. They all follow simple, one-method binding calls, e.g.
 Samplers
 ^^^^^^^^
 
-pipe_sampler_state objects control how textures are sampled
-(coordinate wrap modes, interpolation modes, etc).  Note that
-samplers are not used for texture buffer objects.  That is,
-pipe_context::bind_sampler_views() will not bind a sampler if the corresponding
-sampler view refers to a PIPE_BUFFER resource.
+pipe_sampler_state objects control how textures are sampled (coordinate wrap
+modes, interpolation modes, etc). Samplers are only required for texture
+instructions for which nir_tex_instr_need_sampler returns true. Drivers must
+ignore samplers for other texture instructions. Frontends may or may not bind
+samplers when no texture instruction use them. Notably, frontends may not bind
+samplers for texture buffer objects, which are never accessed with samplers.
 
 Sampler Views
 ^^^^^^^^^^^^^