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

From: Michel Dänzer
Date: Tue Jul 12 2022 - 05:09:41 EST

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).

Earthling Michel Dänzer |
Libre software enthusiast | Mesa and Xwayland developer