isl: Add isl_format_layout::uniform_channel_type

If each format channel has the same base type (such unorm), then that
is the format's "uniform channel type".

Calculating the field at buildtime is probably better than looping over
all channels at runtime each time we wish to query it.

Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>

src/intel/isl/gen_format_layout.py

@@ -81,6 +81,7 @@ isl_format_layouts[] = {
       % endif
     % endfor
     },
+    .uniform_channel_type = ISL_${format.uniform_channel_type},
     .colorspace = ISL_COLORSPACE_${format.colorspace},
     .txc = ISL_TXC_${format.txc},
   },
@@ -179,6 +180,23 @@ class Format(object):
             chan.start = bit
             bit = bit + chan.size
 
+        # Set the uniform channel type, if the format has one.
+        #
+        # Iterate over all channels, not just those in self.order, because
+        # some formats have an empty 'order' field in the CSV (such as
+        # YCRCB_NORMAL).
+        self.uniform_channel_type = 'VOID'
+        for chan in self.channels:
+            if chan.type in (None, 'VOID'):
+                pass
+            elif self.uniform_channel_type == 'VOID':
+                self.uniform_channel_type = chan.type
+            elif self.uniform_channel_type == chan.type:
+                pass
+            else:
+                self.uniform_channel_type = 'VOID'
+                break
+
         # alpha doesn't have a colorspace of it's own.
         self.colorspace = line[13].strip().upper()
         if self.colorspace in ['']:
@@ -188,6 +206,17 @@ class Format(object):
         self.txc = line[14].strip().upper() or 'NONE'
 
 
+    @property
+    def channels(self):
+        yield self.r
+        yield self.g
+        yield self.b
+        yield self.a
+        yield self.l
+        yield self.i
+        yield self.p
+
+
 def reader(csvfile):
     """Wrapper around csv.reader that skips comments and blanks."""
     # csv.reader actually reads the file one line at a time (it was designed to

src/intel/isl/isl.h

@@ -1133,6 +1133,9 @@ struct isl_format_layout {
       struct isl_channel_layout channels_array[7];
    };
 
+   /** Set if all channels have the same isl_base_type. Otherwise, ISL_BASE_VOID. */
+   enum isl_base_type uniform_channel_type;
+
    enum isl_colorspace colorspace;
    enum isl_txc txc;
 };