gallium: Add new cap PIPE_CAP_TEXTURE_BUFFER_SAMPLER

This indicates whether a driver wants samplers for buffer textures as
well as normal textures.

Reviewed-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/8300>

docs/gallium/screen.rst

@@ -165,6 +165,9 @@ The integer capabilities:
   TEXCOORD semantic.
   Also, TGSI_SEMANTIC_PCOORD becomes available, which labels a fragment shader
   input that will always be replaced with sprite coordinates.
+* ``PIPE_CAP_TEXTURE_BUFFER_SAMPLER``: Whether a sampler should still
+  be used for PIPE_BUFFER resources (normally a sampler is only used
+  if the texture target is PIPE_TEXTURE_*).
 * ``PIPE_CAP_PREFER_BLIT_BASED_TEXTURE_TRANSFER``: Whether it is preferable
   to use a blit to implement a texture transfer which needs format conversions
   and swizzling in gallium frontends. Generally, all hardware drivers with

src/gallium/auxiliary/util/u_screen.c

@@ -148,6 +148,7 @@ u_pipe_screen_get_param_defaults(struct pipe_screen *pscreen,
 
    case PIPE_CAP_BUFFER_SAMPLER_VIEW_RGBA_ONLY:
    case PIPE_CAP_TGSI_TEXCOORD:
+   case PIPE_CAP_TEXTURE_BUFFER_SAMPLER:
       return 0;
 
    case PIPE_CAP_PREFER_BLIT_BASED_TEXTURE_TRANSFER:

src/gallium/include/pipe/p_defines.h

@@ -792,6 +792,7 @@ enum pipe_cap
    PIPE_CAP_TEXTURE_BUFFER_OFFSET_ALIGNMENT,
    PIPE_CAP_BUFFER_SAMPLER_VIEW_RGBA_ONLY,
    PIPE_CAP_TGSI_TEXCOORD,
+   PIPE_CAP_TEXTURE_BUFFER_SAMPLER,
    PIPE_CAP_PREFER_BLIT_BASED_TEXTURE_TRANSFER,
    PIPE_CAP_QUERY_PIPELINE_STATISTICS,
    PIPE_CAP_TEXTURE_BORDER_COLOR_QUIRK,

src/mesa/state_tracker/st_context.c

@@ -685,6 +685,8 @@ st_create_context_priv(struct gl_context *ctx, struct pipe_context *pipe,
       !!(screen->get_param(screen, PIPE_CAP_TEXTURE_BORDER_COLOR_QUIRK) &
          (PIPE_QUIRK_TEXTURE_BORDER_COLOR_SWIZZLE_NV50 |
           PIPE_QUIRK_TEXTURE_BORDER_COLOR_SWIZZLE_R600));
+   st->texture_buffer_sampler =
+      screen->get_param(screen, PIPE_CAP_TEXTURE_BUFFER_SAMPLER);
    st->has_time_elapsed =
       screen->get_param(screen, PIPE_CAP_QUERY_TIME_ELAPSED);
    st->has_half_float_packing =

src/mesa/state_tracker/st_context.h

@@ -181,6 +181,7 @@ struct st_context
 
    boolean needs_texcoord_semantic;
    boolean apply_texture_swizzle_to_border_color;
+   boolean texture_buffer_sampler;
 
    /* On old libGL's for linux we need to invalidate the drawables
     * on glViewpport calls, this is set via a option.