+#define PB_USAGE_CPU_READ (1 << 0)
+#define PB_USAGE_CPU_WRITE (1 << 1)
+#define PB_USAGE_GPU_READ (1 << 2)
+#define PB_USAGE_GPU_WRITE (1 << 3)
+#define PB_USAGE_UNSYNCHRONIZED (1 << 10)
+#define PB_USAGE_DONTBLOCK (1 << 9)
+
+#define PB_USAGE_CPU_READ_WRITE \
+ ( PB_USAGE_CPU_READ | PB_USAGE_CPU_WRITE )
+#define PB_USAGE_GPU_READ_WRITE \
+ ( PB_USAGE_GPU_READ | PB_USAGE_GPU_WRITE )
+#define PB_USAGE_WRITE \
+ ( PB_USAGE_CPU_WRITE | PB_USAGE_GPU_WRITE )
+