[Mesa-dev] [Intel-gfx] [PATCH] dri3, i915, i965: Add __DRI_IMAGE_FOURCC_SARGB8888

Keith Packard keithp at keithp.com
Fri Nov 22 15:36:43 PST 2013

Kristian Høgsberg <hoegsberg at gmail.com> writes:

> I already explained to Keith why we use different sets of format codes
> in the DRI interface, but it's always fun to slam other peoples code.

As we discussed, my complaint isn't so much about __DRI_IMAGE_FOURCC,
but the fact that the __DRIimage interfaces use *both*
__DRI_IMAGE_FOURCC and __DRI_IMAGE_FORMAT at different times.

Ok, here's a fine thing we can actually fix -- the pattern that mesa
uses all over the place in converting formats looks like this (not to
pick on anyone, it's repeated everywhere, this is just the first one I
found in gbm_dri.c):

	static uint32_t
        gbm_dri_to_gbm_format(uint32_t dri_format)
	   uint32_t ret = 0;
	   switch (dri_format) {
	   case __DRI_IMAGE_FORMAT_RGB565:
	      ret = GBM_FORMAT_RGB565;
	   case __DRI_IMAGE_FORMAT_XRGB8888:
	      ret = GBM_FORMAT_XRGB8888;
	   case __DRI_IMAGE_FORMAT_ARGB8888:
	      ret = GBM_FORMAT_ARGB8888;
	   case __DRI_IMAGE_FORMAT_ABGR8888:
	      ret = GBM_FORMAT_ABGR8888;
	      ret = 0;
	   return ret;

The problem here is that any unknown incoming formats get translated to
garbage (0) outgoing. With fourcc codes, there is the slight advantage
that 0 is never a legal value, but it sure would be nice to print a
warning or even abort if you get a format code you don't understand as
there's no way 0 is ever going to do what you want.

Anyone have a preference? Abort? Print an error? Silently continue to do
the wrong thing?

keith.packard at intel.com
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