mesa: Add R8G8_R8B8 and G8R8_B8R8 formats

These aren't real formats.  They cannot be used with
RenderbufferObjects, Textures, or anything else visible through the GL
API.  The only purpose is to support YUYV textures imported through
EGL_image_external.  There is hardware that can sample from this
subsampled format, but the hardware does not do the colorspace
conversion automatically.

v2: Treat these formats as compressed.  This is a lie, but it seems to
be a less egregious lie than what I was doing before.  It also passes
'ninja test'.

Reviewed-by: Emma Anholt <emma@anholt.net>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/9610>

src/mesa/main/format_info.py

@@ -128,6 +128,8 @@ def get_channel_bits(fmat, chan_name):
          return bits if fmat.has_channel(chan_name) else 0
       elif fmat.layout == 'atc':
          return 8 if fmat.has_channel(chan_name) else 0
+      elif fmat.layout == 'other' and ('RG_RB' in fmat.name or 'GR_BR' in fmat.name):
+         return 8 if fmat.has_channel(chan_name) else 0
       else:
          assert False
    else:

src/mesa/main/format_parser.py

@@ -518,7 +518,7 @@ def _get_datatype(type, size):
    else:
       assert False
 
-def _parse_channels(fields, layout, colorspace, swizzle):
+def _parse_channels(fields):
    channels = []
    for field in fields:
       if not field:
@@ -569,6 +569,7 @@ def parse(filename):
             swizzle = Swizzle(fields[9])
          except:
             sys.exit("error parsing swizzle for format " + name)
-         channels = _parse_channels(fields[5:9], layout, colorspace, swizzle)
+
+         channels = _parse_channels(fields[5:9])
 
          yield Format(name, layout, block_width, block_height, block_depth, channels, swizzle, colorspace)

src/mesa/main/formats.c

@@ -1024,6 +1024,8 @@ _mesa_uncompressed_format_to_type_and_comps(mesa_format format,
 
    case MESA_FORMAT_YCBCR:
    case MESA_FORMAT_YCBCR_REV:
+   case MESA_FORMAT_RG_RB_UNORM8:
+   case MESA_FORMAT_GR_BR_UNORM8:
       *datatype = GL_UNSIGNED_SHORT;
       *comps = 2;
       return;

src/mesa/main/formats.csv

@@ -93,6 +93,9 @@ MESA_FORMAT_A2R10G10B10_UNORM             , packed, 1, 1, 1, un2 , un10, un10, u
 MESA_FORMAT_YCBCR                         , other , 1, 1, 1, x16 ,     ,     ,     , xyzw, yuv
 MESA_FORMAT_YCBCR_REV                     , other , 1, 1, 1, x16 ,     ,     ,     , xyzw, yuv
 
+MESA_FORMAT_RG_RB_UNORM8                  , other , 2, 1, 1, x16 ,     ,     ,     , xyz1, rgb
+MESA_FORMAT_GR_BR_UNORM8                  , other , 2, 1, 1, x16 ,     ,     ,     , xyz1, rgb
+
 # Array normalized formats
 MESA_FORMAT_A_UNORM8                      , array , 1, 1, 1, un8 ,     ,     ,     , 000x, rgb
 MESA_FORMAT_A_UNORM16                     , array , 1, 1, 1, un16,     ,     ,     , 000x, rgb

src/mesa/main/formats.h

@@ -385,6 +385,8 @@ typedef enum pipe_format mesa_format;
 #define MESA_FORMAT_A2R10G10B10_UNORM            PIPE_FORMAT_A2R10G10B10_UNORM
 #define MESA_FORMAT_YCBCR                        PIPE_FORMAT_UYVY
 #define MESA_FORMAT_YCBCR_REV                    PIPE_FORMAT_YUYV
+#define MESA_FORMAT_RG_RB_UNORM8                 PIPE_FORMAT_R8G8_R8B8_UNORM
+#define MESA_FORMAT_GR_BR_UNORM8                 PIPE_FORMAT_G8R8_B8R8_UNORM
 #define MESA_FORMAT_A_UNORM8                     PIPE_FORMAT_A8_UNORM
 #define MESA_FORMAT_A_UNORM16                    PIPE_FORMAT_A16_UNORM
 #define MESA_FORMAT_L_UNORM8                     PIPE_FORMAT_L8_UNORM