gallium: add a cap for VIEWPORT_SUBPIXEL_BITS (v2)

This allows Gallium drivers to advertise the subpixel precision
for floating point viewports bounds.

v2:
  - Set ViewportSubpixelBits in st_init_limits.

Signed-off-by: Józef Kucia <joseph.kucia@gmail.com>
Signed-off-by: Marek Olšák <marek.olsak@amd.com>
Reviewed-by: Ilia Mirkin <imirkin@alum.mit.edu>

src/gallium/docs/source/screen.rst

@@ -345,6 +345,8 @@ The integer capabilities:
   supported in ``set_window_rectangles``.
 * ``PIPE_CAP_POLYGON_OFFSET_UNITS_UNSCALED``: If true, the driver implements support
   for ``pipe_rasterizer_state::offset_units_unscaled``.
+* ``PIPE_CAP_VIEWPORT_SUBPIXEL_BITS``: Number of bits of subpixel precision for
+  floating point viewport bounds.
 
 
 .. _pipe_capf:

src/gallium/drivers/freedreno/freedreno_screen.c

@@ -267,6 +267,7 @@ fd_screen_get_param(struct pipe_screen *pscreen, enum pipe_cap param)
 	case PIPE_CAP_TGSI_VOTE:
 	case PIPE_CAP_MAX_WINDOW_RECTANGLES:
 	case PIPE_CAP_POLYGON_OFFSET_UNITS_UNSCALED:
+	case PIPE_CAP_VIEWPORT_SUBPIXEL_BITS:
 		return 0;
 
 	case PIPE_CAP_MAX_VIEWPORTS:

src/gallium/drivers/i915/i915_screen.c

@@ -290,6 +290,7 @@ i915_get_param(struct pipe_screen *screen, enum pipe_cap cap)
    case PIPE_CAP_MULTI_DRAW_INDIRECT_PARAMS:
    case PIPE_CAP_TGSI_FS_FINE_DERIVATIVE:
    case PIPE_CAP_SAMPLER_VIEW_TARGET:
+   case PIPE_CAP_VIEWPORT_SUBPIXEL_BITS:
       return 0;
 
    case PIPE_CAP_MAX_VIEWPORTS:

src/gallium/drivers/ilo/ilo_screen.c

@@ -505,6 +505,7 @@ ilo_get_param(struct pipe_screen *screen, enum pipe_cap param)
    case PIPE_CAP_TGSI_VOTE:
    case PIPE_CAP_MAX_WINDOW_RECTANGLES:
    case PIPE_CAP_POLYGON_OFFSET_UNITS_UNSCALED:
+   case PIPE_CAP_VIEWPORT_SUBPIXEL_BITS:
       return 0;
 
    case PIPE_CAP_VENDOR_ID:

src/gallium/drivers/llvmpipe/lp_screen.c

@@ -328,6 +328,7 @@ llvmpipe_get_param(struct pipe_screen *screen, enum pipe_cap param)
    case PIPE_CAP_TGSI_VOTE:
    case PIPE_CAP_MAX_WINDOW_RECTANGLES:
    case PIPE_CAP_POLYGON_OFFSET_UNITS_UNSCALED:
+   case PIPE_CAP_VIEWPORT_SUBPIXEL_BITS:
       return 0;
    }
    /* should only get here on unhandled cases */

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

@@ -199,6 +199,7 @@ nv30_screen_get_param(struct pipe_screen *pscreen, enum pipe_cap param)
    case PIPE_CAP_TGSI_VOTE:
    case PIPE_CAP_MAX_WINDOW_RECTANGLES:
    case PIPE_CAP_POLYGON_OFFSET_UNITS_UNSCALED:
+   case PIPE_CAP_VIEWPORT_SUBPIXEL_BITS:
       return 0;
 
    case PIPE_CAP_VENDOR_ID:

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

@@ -253,6 +253,7 @@ nv50_screen_get_param(struct pipe_screen *pscreen, enum pipe_cap param)
    case PIPE_CAP_PRIMITIVE_RESTART_FOR_PATCHES:
    case PIPE_CAP_TGSI_VOTE:
    case PIPE_CAP_POLYGON_OFFSET_UNITS_UNSCALED:
+   case PIPE_CAP_VIEWPORT_SUBPIXEL_BITS:
       return 0;
 
    case PIPE_CAP_VENDOR_ID:

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

@@ -272,6 +272,7 @@ nvc0_screen_get_param(struct pipe_screen *pscreen, enum pipe_cap param)
    case PIPE_CAP_PCI_BUS:
    case PIPE_CAP_PCI_DEVICE:
    case PIPE_CAP_PCI_FUNCTION:
+   case PIPE_CAP_VIEWPORT_SUBPIXEL_BITS:
       return 0;
 
    case PIPE_CAP_VENDOR_ID:

src/gallium/drivers/r300/r300_screen.c

@@ -221,6 +221,7 @@ static int r300_get_param(struct pipe_screen* pscreen, enum pipe_cap param)
         case PIPE_CAP_TGSI_VOTE:
         case PIPE_CAP_MAX_WINDOW_RECTANGLES:
         case PIPE_CAP_POLYGON_OFFSET_UNITS_UNSCALED:
+        case PIPE_CAP_VIEWPORT_SUBPIXEL_BITS:
             return 0;
 
         /* SWTCL-only features. */

src/gallium/drivers/r600/r600_pipe.c

@@ -371,6 +371,7 @@ static int r600_get_param(struct pipe_screen* pscreen, enum pipe_cap param)
 	case PIPE_CAP_PRIMITIVE_RESTART_FOR_PATCHES:
 	case PIPE_CAP_TGSI_VOTE:
 	case PIPE_CAP_MAX_WINDOW_RECTANGLES:
+	case PIPE_CAP_VIEWPORT_SUBPIXEL_BITS:
 		return 0;
 
 	case PIPE_CAP_MAX_SHADER_PATCH_VARYINGS:

src/gallium/drivers/radeonsi/si_pipe.c

@@ -444,6 +444,7 @@ static int si_get_param(struct pipe_screen* pscreen, enum pipe_cap param)
 	case PIPE_CAP_PRIMITIVE_RESTART_FOR_PATCHES:
 	case PIPE_CAP_TGSI_VOTE:
 	case PIPE_CAP_MAX_WINDOW_RECTANGLES:
+	case PIPE_CAP_VIEWPORT_SUBPIXEL_BITS:
 		return 0;
 
 	case PIPE_CAP_MAX_SHADER_PATCH_VARYINGS:

src/gallium/drivers/softpipe/sp_screen.c

@@ -278,6 +278,7 @@ softpipe_get_param(struct pipe_screen *screen, enum pipe_cap param)
    case PIPE_CAP_TGSI_VOTE:
    case PIPE_CAP_MAX_WINDOW_RECTANGLES:
    case PIPE_CAP_POLYGON_OFFSET_UNITS_UNSCALED:
+   case PIPE_CAP_VIEWPORT_SUBPIXEL_BITS:
       return 0;
    case PIPE_CAP_SHADER_BUFFER_OFFSET_ALIGNMENT:
       return 4;

src/gallium/drivers/svga/svga_screen.c

@@ -412,6 +412,7 @@ svga_get_param(struct pipe_screen *screen, enum pipe_cap param)
    case PIPE_CAP_TGSI_VOTE:
    case PIPE_CAP_MAX_WINDOW_RECTANGLES:
    case PIPE_CAP_POLYGON_OFFSET_UNITS_UNSCALED:
+   case PIPE_CAP_VIEWPORT_SUBPIXEL_BITS:
       return 0;
    }
 

src/gallium/drivers/swr/swr_screen.cpp

@@ -364,6 +364,7 @@ swr_get_param(struct pipe_screen *screen, enum pipe_cap param)
    case PIPE_CAP_TGSI_VOTE:
    case PIPE_CAP_MAX_WINDOW_RECTANGLES:
    case PIPE_CAP_POLYGON_OFFSET_UNITS_UNSCALED:
+   case PIPE_CAP_VIEWPORT_SUBPIXEL_BITS:
       return 0;
    }
 

src/gallium/drivers/vc4/vc4_screen.c

@@ -217,6 +217,7 @@ vc4_screen_get_param(struct pipe_screen *pscreen, enum pipe_cap param)
         case PIPE_CAP_TGSI_VOTE:
         case PIPE_CAP_MAX_WINDOW_RECTANGLES:
         case PIPE_CAP_POLYGON_OFFSET_UNITS_UNSCALED:
+        case PIPE_CAP_VIEWPORT_SUBPIXEL_BITS:
                 return 0;
 
                 /* Stream output. */

src/gallium/drivers/virgl/virgl_screen.c

@@ -246,6 +246,7 @@ virgl_get_param(struct pipe_screen *screen, enum pipe_cap param)
    case PIPE_CAP_TGSI_VOTE:
    case PIPE_CAP_MAX_WINDOW_RECTANGLES:
    case PIPE_CAP_POLYGON_OFFSET_UNITS_UNSCALED:
+   case PIPE_CAP_VIEWPORT_SUBPIXEL_BITS:
       return 0;
    case PIPE_CAP_VENDOR_ID:
       return 0x1af4;

src/gallium/include/pipe/p_defines.h

@@ -732,6 +732,7 @@ enum pipe_cap
    PIPE_CAP_TGSI_VOTE,
    PIPE_CAP_MAX_WINDOW_RECTANGLES,
    PIPE_CAP_POLYGON_OFFSET_UNITS_UNSCALED,
+   PIPE_CAP_VIEWPORT_SUBPIXEL_BITS,
 };
 
 #define PIPE_QUIRK_TEXTURE_BORDER_COLOR_SWIZZLE_NV50 (1 << 0)

src/mesa/state_tracker/st_extensions.c

@@ -105,6 +105,9 @@ void st_init_limits(struct pipe_screen *screen,
    c->MaxViewportHeight =
    c->MaxRenderbufferSize = c->MaxTextureRectSize;
 
+   c->ViewportSubpixelBits =
+      screen->get_param(screen, PIPE_CAP_VIEWPORT_SUBPIXEL_BITS);
+
    c->MaxDrawBuffers = c->MaxColorAttachments =
       _clamp(screen->get_param(screen, PIPE_CAP_MAX_RENDER_TARGETS),
              1, MAX_DRAW_BUFFERS);