On 03/05/17 12:06 AM, Gerd Hoffmann wrote: > >> Removing the definition also removes the possibility to describe a lot >> of pixel formats, so that should definitely be mentioned. I think it >> would also be good to have some kind of justified claim that no >> hardware actually needs the pixel formats this is removing (e.g. RGB565 >> BE). > > That and RGB2101010 BE are the only candidates I can think of. > > Dealing with those in none-native byteorder is a PITA though. Display > hardware is little endian (pci byte order) for quite a while already. Maybe by default, but not exclusively. > radeon looks differently on pre-R600 and R600+ hardware. > > pre-R600 can byteswap on cpu access, so the cpu view is bigendian > whereas things are actually stored on little endian byte order. > Hardware supports both 16bit and 32bit swaps. Used for fbdev emulation > (probably 32bit swaps, but not fully sure). 32-bit swaps for 32 bpp, 16-bit swaps for 16 bpp. > R600+ supports bigendian framebuffer formats, so no byteswapping on > access is needed. Not sure whenever that includes 16bpp formats or > whenever this is limited to the 8 bit-per-color formats [...] It includes 16bpp. Looking at drivers/gpu/drm/radeon/atombios_crtc.c:dce4_crtc_do_set_base(), it sets up byte-swapping for all multi-byte formats, so it effectively treats all those formats as if they had DRM_FORMAT_BIG_ENDIAN set. If the radeon (and amdgpu) driver were to be changed to use drm_mode_legacy_fb_format_he for >= R600, that must also handle 16 bpp, which requires DRM_FORMAT_BIG_ENDIAN. So I still don't see how that can be removed or even deprecated. >From Ilia's followup it sounds like there's a similar situation with nouveau. -- Earthling Michel Dänzer | http://www.amd.com Libre software enthusiast | Mesa and X developer
