Re: [PATCH 1/3] drm: fourcc byteorder: drop DRM_FORMAT_BIG_ENDIAN

From	Michel Dänzer <michel@daenzer.net>
Newsgroups	linux.kernel
Subject	Re: [PATCH 1/3] drm: fourcc byteorder: drop DRM_FORMAT_BIG_ENDIAN
Date	2017-05-08 02:40 +0200
Message-ID	<tEESt-4Zk-11@gated-at.bofh.it> (permalink)
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On 03/05/17 06:24 PM, Gerd Hoffmann wrote:
>   Hi,
> 
>>> 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.
> 
> Ok.
> 
> Dropped patch #1.
> 
> Updated patch #2 to include all formats returned by
> drm_mode_legacy_fb_format, and also renamed them to DRM_FORMAT_HOST_*.
> 
> Question is how to go forward with patch #3.  I'd prefer to not add
> drm_mode_legacy_fb_format_he if possible.  Is there a chance to adapt
> the radeon and nvidia drivers to a fixed drm_mode_legacy_fb_format
> function (returning be formats on be) without invasive changes?  Given
> they both treat formats as if they had DRM_FORMAT_BIG_ENDIAN set this
> could (with the help of the extended patch #2) be a simple
> s/DRM_FORMAT_/DRM_FORMAT_HOST/ at the right places ...

For radeon this doesn't work with pre-R600 GPUs, which only support
little endian formats for display.


-- 
Earthling Michel Dänzer               |               http://www.amd.com
Libre software enthusiast             |             Mesa and X developer

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[PATCH 1/3] drm: fourcc byteorder: drop DRM_FORMAT_BIG_ENDIAN Gerd Hoffmann <kraxel@redhat.com> - 2017-05-02 15:40 +0200
  Re: [PATCH 1/3] drm: fourcc byteorder: drop DRM_FORMAT_BIG_ENDIAN Emil Velikov <emil.l.velikov@gmail.com> - 2017-05-02 16:00 +0200
    Re: [PATCH 1/3] drm: fourcc byteorder: drop DRM_FORMAT_BIG_ENDIAN Gerd Hoffmann <kraxel@redhat.com> - 2017-05-02 16:20 +0200
    Re: [PATCH 1/3] drm: fourcc byteorder: drop DRM_FORMAT_BIG_ENDIAN Pekka Paalanen <ppaalanen@gmail.com> - 2017-05-02 16:30 +0200
      Re: [PATCH 1/3] drm: fourcc byteorder: drop DRM_FORMAT_BIG_ENDIAN Gerd Hoffmann <kraxel@redhat.com> - 2017-05-02 17:10 +0200
        Re: [PATCH 1/3] drm: fourcc byteorder: drop DRM_FORMAT_BIG_ENDIAN Ilia Mirkin <imirkin@alum.mit.edu> - 2017-05-02 20:00 +0200
        Re: [PATCH 1/3] drm: fourcc byteorder: drop DRM_FORMAT_BIG_ENDIAN Michel Dänzer <michel@daenzer.net> - 2017-05-03 05:10 +0200
          Re: [PATCH 1/3] drm: fourcc byteorder: drop DRM_FORMAT_BIG_ENDIAN Gerd Hoffmann <kraxel@redhat.com> - 2017-05-03 11:30 +0200
            Re: [PATCH 1/3] drm: fourcc byteorder: drop DRM_FORMAT_BIG_ENDIAN Michel Dänzer <michel@daenzer.net> - 2017-05-08 02:40 +0200

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