Re: [PATCH 1/3] drm/fourcc: Add missing big-endian XRGB1555 and RGB565 formats

From: Geert Uytterhoeven
Date: Tue Jul 12 2022 - 05:11:02 EST

Hi Michel,

On Tue, Jul 12, 2022 at 11:09 AM Michel Dänzer
<michel.daenzer@xxxxxxxxxxx> wrote:
> On 2022-07-12 11:03, Gerd Hoffmann wrote:
> >>> As described above DRM_FORMAT_HOST_RGB565 means bigendian on bigendian
> >>> hosts and little endian on little endian hosts. Which is not correct
> >>> when your hardware does big endian no matter what.
> >>
> >> But (a) drm_driver_legacy_fb_format() uses DRM_FORMAT_HOST_RGB565
> >> if quirk_addfb_prefer_host_byte_order is set,
> >
> > Ah, right. Missed that in 'git grep' output. Given that traditional
> > fbdev behavior is to expect native byte order using
> > DRM_FORMAT_HOST_RGB565 there makes sense indeed.
> >
> > Scratch my comment about it being unused then ;)
> DRM_FORMAT_RGB565 | DRM_FORMAT_BIG_ENDIAN is still what the driver should use conceptually, and should match DRM_FORMAT_HOST_RGB565 in drm_driver_legacy_fb_format on a big endian host (which is presumably always the case for the atari driver).

Sure, I'll update the patch accordingly.



Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds