On Thu, May 11, 2017 at 11:23:11PM +0200, Pavel Machek wrote: > On Fri 2017-04-21 14:08:04, Ville Syrjälä wrote: > > On Fri, Apr 21, 2017 at 11:50:18AM +0200, Gerd Hoffmann wrote: > > > On Fr, 2017-04-21 at 12:25 +0300, Ville Syrjälä wrote: > > > > On Fri, Apr 21, 2017 at 09:58:24AM +0200, Gerd Hoffmann wrote: > > > > > While working on graphics support for virtual machines on ppc64 (which > > > > > exists in both little and big endian variants) I've figured the comments > > > > > for various drm fourcc formats in the header file don't match reality. > > > > > > > > > > Comments says the RGB formats are little endian, but in practice they > > > > > are native endian. Look at the drm_mode_legacy_fb_format() helper. It > > > > > maps -- for example -- bpp/depth 32/24 to DRM_FORMAT_XRGB8888, no matter > > > > > whenever the machine is little endian or big endian. The users of this > > > > > function (fbdev emulation, DRM_IOCTL_MODE_ADDFB) expect the framebuffer > > > > > is native endian, not little endian. Most userspace also operates on > > > > > native endian only. > > > > > > > > I'm not a fan of "native". Native to what? "CPU" or "host" is what I'd > > > > call it. > > > > > > native == whatever the cpu is using. > > > > > > I personally find "native" more intuitive, but at the end of the day I > > > don't mind much. If people prefer "host" over "native" I'll change it. > > > > "native" to me feels more like "native to the GPU" since these things > > really are tied to the GPU not the CPU. That's also why I went with the > > explicit endianness originally so that the driver could properly declare > > what the GPU supports. > > You can easily have more than one GPU in the system. Plus these are > used by cameras / frame grabbers, too. So anything else than CPU > endianness is badly defined. The framebuffer has very little to do with the CPU. The display controller is the only consumer, and the producer could be whatever. -- Ville Syrjälä Intel OTC
