gallium: Add UNSYNCHRONIZED cpu access flag. Document others.

src/gallium/include/pipe/p_defines.h

@@ -225,9 +225,10 @@ enum pipe_transfer_usage {
 };
 
 
-/**
+/*
  * Buffer usage flags
  */
+
 #define PIPE_BUFFER_USAGE_CPU_READ  (1 << 0)
 #define PIPE_BUFFER_USAGE_CPU_WRITE (1 << 1)
 #define PIPE_BUFFER_USAGE_GPU_READ  (1 << 2)
@@ -236,9 +237,63 @@ enum pipe_transfer_usage {
 #define PIPE_BUFFER_USAGE_VERTEX    (1 << 5)
 #define PIPE_BUFFER_USAGE_INDEX     (1 << 6)
 #define PIPE_BUFFER_USAGE_CONSTANT  (1 << 7)
+
+/*
+ * CPU access flags.
+ *
+ * These flags should only be used for texture transfers or when mapping
+ * buffers.
+ *
+ * Note that the PIPE_BUFFER_USAGE_CPU_xxx flags above are also used for
+ * mapping. Either PIPE_BUFFER_USAGE_CPU_READ or PIPE_BUFFER_USAGE_CPU_WRITE
+ * must be set.
+ */
+
+/**
+ * Discards the memory within the mapped region.
+ *
+ * It should not be used with PIPE_BUFFER_USAGE_CPU_READ.
+ *
+ * See also:
+ * - OpenGL's ARB_map_buffer_range extension, MAP_INVALIDATE_RANGE_BIT flag.
+ * - Direct3D's D3DLOCK_DISCARD flag.
+ */
 #define PIPE_BUFFER_USAGE_DISCARD   (1 << 8)
+
+/**
+ * Fail if the resource cannot be mapped immediately.
+ *
+ * See also:
+ * - Direct3D's D3DLOCK_DONOTWAIT flag.
+ * - Mesa3D's MESA_MAP_NOWAIT_BIT flag.
+ * - WDDM's D3DDDICB_LOCKFLAGS.DonotWait flag.
+ */
 #define PIPE_BUFFER_USAGE_DONTBLOCK (1 << 9)
-#define PIPE_BUFFER_USAGE_FLUSH_EXPLICIT (1 << 10) /**< See pipe_screen::buffer_flush_mapped_range */
+
+/**
+ * Do not attempt to synchronize pending operations on the resource when mapping.
+ *
+ * It should not be used with PIPE_BUFFER_USAGE_CPU_READ.
+ *
+ * See also:
+ * - OpenGL's ARB_map_buffer_range extension, MAP_UNSYNCHRONIZED_BIT flag.
+ * - Direct3D's D3DLOCK_NOOVERWRITE flag.
+ * - WDDM's D3DDDICB_LOCKFLAGS.IgnoreSync flag.
+ */
+#define PIPE_BUFFER_USAGE_UNSYNCHRONIZED (1 << 10)
+
+/**
+ * Written ranges will be notified later with
+ * pipe_screen::buffer_flush_mapped_range.
+ *
+ * It should not be used with PIPE_BUFFER_USAGE_CPU_READ.
+ *
+ * See also:
+ * - pipe_screen::buffer_flush_mapped_range
+ * - OpenGL's ARB_map_buffer_range extension, MAP_FLUSH_EXPLICIT_BIT flag.
+ */
+#define PIPE_BUFFER_USAGE_FLUSH_EXPLICIT (1 << 11)
+
 /** Pipe driver custom usage flags should be greater or equal to this value */
 #define PIPE_BUFFER_USAGE_CUSTOM    (1 << 16)