gallium: add PIPE_CAP_MAX_VERTEX_BUFFERS

Add PIPE_CAP_MAX_VERTEX_BUFFERS param, which defaults to 16.

Signed-off-by: Christian Gmeiner <christian.gmeiner@gmail.com>
Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/merge_requests/2807>

src/gallium/auxiliary/util/u_screen.c

@@ -401,6 +401,9 @@ u_pipe_screen_get_param_defaults(struct pipe_screen *pscreen,
    case PIPE_CAP_CLIP_PLANES:
       return 1;
 
+   case PIPE_CAP_MAX_VERTEX_BUFFERS:
+      return 16;
+
    default:
       unreachable("bad PIPE_CAP_*");
    }

src/gallium/docs/source/screen.rst

@@ -564,6 +564,7 @@ The integer capabilities:
   as opposed to writing gl_PointSize for every point.
 * ``PIPE_CAP_TWO_SIDED_COLOR``: Driver supports two-sided coloring.
 * ``PIPE_CAP_CLIP_PLANES``: Driver supports user-defined clip-planes.
+* ``PIPE_CAP_MAX_VERTEX_BUFFERS``: Number of supported vertex buffers.
 
 .. _pipe_capf:
 

src/gallium/include/pipe/p_defines.h

@@ -909,6 +909,7 @@ enum pipe_cap
    PIPE_CAP_POINT_SIZE_FIXED,
    PIPE_CAP_TWO_SIDED_COLOR,
    PIPE_CAP_CLIP_PLANES,
+   PIPE_CAP_MAX_VERTEX_BUFFERS,
 };
 
 /**