gallium: Add PIPE_CAP_BUFFER_SAMPLER_VIEW_RGBA_ONLY

This cap indicates that the driver only supports R, RG, RGB and RGBA
formats for PIPE_BUFFER sampler views.

v2: move into "unsupported features" section for nouveau (Ilia Mirkin)

Reviewed-by: Edward O'Callaghan <eocallaghan@alterapraxis.com>

src/gallium/docs/source/screen.rst

@@ -138,6 +138,10 @@ The integer capabilities:
 * ``PIPE_CAP_TEXTURE_BUFFER_OFFSET_ALIGNMENT``: Describes the required
   alignment for pipe_sampler_view::u.buf.first_element, in bytes.
   If a driver does not support first/last_element, it should return 0.
+* ``PIPE_CAP_BUFFER_SAMPLER_VIEW_RGBA_ONLY``: Whether the driver only
+  supports R, RG, RGB and RGBA formats for PIPE_BUFFER sampler views.
+  When this is the case it should be assumed that the swizzle parameters
+  in the sampler view have no effect.
 * ``PIPE_CAP_TGSI_TEXCOORD``: This CAP describes a hw limitation.
   If true, the hardware cannot replace arbitrary shader inputs with sprite
   coordinates and hence the inputs that are desired to be replaceable must

src/gallium/drivers/freedreno/freedreno_screen.c

@@ -183,6 +183,8 @@ fd_screen_get_param(struct pipe_screen *pscreen, enum pipe_cap param)
 	case PIPE_CAP_CLIP_HALFZ:
 		return is_a3xx(screen) || is_a4xx(screen);
 
+	case PIPE_CAP_BUFFER_SAMPLER_VIEW_RGBA_ONLY:
+		return 0;
 	case PIPE_CAP_TEXTURE_BUFFER_OFFSET_ALIGNMENT:
 		if (is_a3xx(screen)) return 16;
 		if (is_a4xx(screen)) return 32;

src/gallium/drivers/i915/i915_screen.c

@@ -262,6 +262,7 @@ i915_get_param(struct pipe_screen *screen, enum pipe_cap cap)
    case PIPE_CAP_INVALIDATE_BUFFER:
    case PIPE_CAP_GENERATE_MIPMAP:
    case PIPE_CAP_STRING_MARKER:
+   case PIPE_CAP_BUFFER_SAMPLER_VIEW_RGBA_ONLY:
       return 0;
 
    case PIPE_CAP_MAX_DUAL_SOURCE_RENDER_TARGETS:

src/gallium/drivers/ilo/ilo_screen.c

@@ -428,6 +428,8 @@ ilo_get_param(struct pipe_screen *screen, enum pipe_cap param)
    case PIPE_CAP_CUBE_MAP_ARRAY:
    case PIPE_CAP_TEXTURE_BUFFER_OBJECTS:
       return true;
+   case PIPE_CAP_BUFFER_SAMPLER_VIEW_RGBA_ONLY:
+      return 0;
    case PIPE_CAP_TEXTURE_BUFFER_OFFSET_ALIGNMENT:
       return 1;
    case PIPE_CAP_TGSI_TEXCOORD:

src/gallium/drivers/llvmpipe/lp_screen.c

@@ -311,6 +311,7 @@ llvmpipe_get_param(struct pipe_screen *screen, enum pipe_cap param)
    case PIPE_CAP_INVALIDATE_BUFFER:
    case PIPE_CAP_GENERATE_MIPMAP:
    case PIPE_CAP_STRING_MARKER:
+   case PIPE_CAP_BUFFER_SAMPLER_VIEW_RGBA_ONLY:
       return 0;
    }
    /* should only get here on unhandled cases */

src/gallium/drivers/nouveau/nv30/nv30_screen.c

@@ -184,6 +184,7 @@ nv30_screen_get_param(struct pipe_screen *pscreen, enum pipe_cap param)
    case PIPE_CAP_INVALIDATE_BUFFER:
    case PIPE_CAP_GENERATE_MIPMAP:
    case PIPE_CAP_STRING_MARKER:
+   case PIPE_CAP_BUFFER_SAMPLER_VIEW_RGBA_ONLY:
       return 0;
 
    case PIPE_CAP_VENDOR_ID:

src/gallium/drivers/nouveau/nv50/nv50_screen.c

@@ -227,6 +227,7 @@ nv50_screen_get_param(struct pipe_screen *pscreen, enum pipe_cap param)
    case PIPE_CAP_INVALIDATE_BUFFER:
    case PIPE_CAP_GENERATE_MIPMAP:
    case PIPE_CAP_STRING_MARKER:
+   case PIPE_CAP_BUFFER_SAMPLER_VIEW_RGBA_ONLY:
       return 0;
 
    case PIPE_CAP_VENDOR_ID:

src/gallium/drivers/nouveau/nvc0/nvc0_screen.c

@@ -217,6 +217,7 @@ nvc0_screen_get_param(struct pipe_screen *pscreen, enum pipe_cap param)
    case PIPE_CAP_INVALIDATE_BUFFER:
    case PIPE_CAP_GENERATE_MIPMAP:
    case PIPE_CAP_STRING_MARKER:
+   case PIPE_CAP_BUFFER_SAMPLER_VIEW_RGBA_ONLY:
       return 0;
 
    case PIPE_CAP_VENDOR_ID:

src/gallium/drivers/r300/r300_screen.c

@@ -210,6 +210,7 @@ static int r300_get_param(struct pipe_screen* pscreen, enum pipe_cap param)
         case PIPE_CAP_INVALIDATE_BUFFER:
         case PIPE_CAP_GENERATE_MIPMAP:
         case PIPE_CAP_STRING_MARKER:
+        case PIPE_CAP_BUFFER_SAMPLER_VIEW_RGBA_ONLY:
             return 0;
 
         /* SWTCL-only features. */

src/gallium/drivers/r600/r600_pipe.c

@@ -342,6 +342,9 @@ static int r600_get_param(struct pipe_screen* pscreen, enum pipe_cap param)
 		/* kernel command checker support is also required */
 		return family >= CHIP_CEDAR && rscreen->b.info.drm_minor >= 41;
 
+	case PIPE_CAP_BUFFER_SAMPLER_VIEW_RGBA_ONLY:
+		return family >= CHIP_CEDAR ? 0 : 1;
+
 	/* Unsupported features. */
 	case PIPE_CAP_TGSI_FS_COORD_ORIGIN_LOWER_LEFT:
 	case PIPE_CAP_TGSI_FS_COORD_PIXEL_CENTER_INTEGER:

src/gallium/drivers/radeonsi/si_pipe.c

@@ -339,6 +339,9 @@ static int si_get_param(struct pipe_screen* pscreen, enum pipe_cap param)
 	case PIPE_CAP_MAX_TEXTURE_BUFFER_SIZE:
 		return MIN2(sscreen->b.info.vram_size, 0xFFFFFFFF);
 
+	case PIPE_CAP_BUFFER_SAMPLER_VIEW_RGBA_ONLY:
+		return 0;
+
 	/* Unsupported features. */
 	case PIPE_CAP_TGSI_FS_COORD_ORIGIN_LOWER_LEFT:
 	case PIPE_CAP_TGSI_CAN_COMPACT_CONSTANTS:

src/gallium/drivers/softpipe/sp_screen.c

@@ -179,6 +179,8 @@ softpipe_get_param(struct pipe_screen *screen, enum pipe_cap param)
       return 1;
    case PIPE_CAP_TEXTURE_BUFFER_OBJECTS:
       return 1;
+   case PIPE_CAP_BUFFER_SAMPLER_VIEW_RGBA_ONLY:
+      return 0;
    case PIPE_CAP_MAX_TEXTURE_BUFFER_SIZE:
       return 65536;
    case PIPE_CAP_TEXTURE_BUFFER_OFFSET_ALIGNMENT:

src/gallium/drivers/svga/svga_screen.c

@@ -396,6 +396,7 @@ svga_get_param(struct pipe_screen *screen, enum pipe_cap param)
    case PIPE_CAP_DRAW_PARAMETERS:
    case PIPE_CAP_TGSI_FS_POSITION_IS_SYSVAL:
    case PIPE_CAP_TGSI_FS_FACE_IS_INTEGER_SYSVAL:
+   case PIPE_CAP_BUFFER_SAMPLER_VIEW_RGBA_ONLY:
       return 0;
    }
 

src/gallium/drivers/vc4/vc4_screen.c

@@ -127,6 +127,7 @@ vc4_screen_get_param(struct pipe_screen *pscreen, enum pipe_cap param)
                 /* Unsupported features. */
         case PIPE_CAP_ANISOTROPIC_FILTER:
         case PIPE_CAP_TEXTURE_BUFFER_OBJECTS:
+        case PIPE_CAP_BUFFER_SAMPLER_VIEW_RGBA_ONLY:
         case PIPE_CAP_CUBE_MAP_ARRAY:
         case PIPE_CAP_TEXTURE_MIRROR_CLAMP:
         case PIPE_CAP_VERTEX_ELEMENT_INSTANCE_DIVISOR:

src/gallium/drivers/virgl/virgl_screen.c

@@ -169,6 +169,8 @@ virgl_get_param(struct pipe_screen *screen, enum pipe_cap param)
       return vscreen->caps.caps.v1.max_tbo_size > 0;
    case PIPE_CAP_TEXTURE_BUFFER_OFFSET_ALIGNMENT:
       return 0;
+   case PIPE_CAP_BUFFER_SAMPLER_VIEW_RGBA_ONLY:
+      return 0;
    case PIPE_CAP_CUBE_MAP_ARRAY:
       return vscreen->caps.caps.v1.bset.cube_map_array;
    case PIPE_CAP_TEXTURE_MULTISAMPLE:

src/gallium/include/pipe/p_defines.h

@@ -589,6 +589,7 @@ enum pipe_cap
    PIPE_CAP_CUBE_MAP_ARRAY,
    PIPE_CAP_TEXTURE_BUFFER_OBJECTS,
    PIPE_CAP_TEXTURE_BUFFER_OFFSET_ALIGNMENT,
+   PIPE_CAP_BUFFER_SAMPLER_VIEW_RGBA_ONLY,
    PIPE_CAP_TGSI_TEXCOORD,
    PIPE_CAP_PREFER_BLIT_BASED_TEXTURE_TRANSFER,
    PIPE_CAP_QUERY_PIPELINE_STATISTICS,