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

From	Gerd Hoffmann <kraxel@redhat.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH 1/3] drm: fourcc byteorder: drop DRM_FORMAT_BIG_ENDIAN
Date	2017-05-03 11:30 +0200
Message-ID	<tCYLD-3gi-1@gated-at.bofh.it> (permalink)
References	(1 earlier) <tCGc2-7i0-13@gated-at.bofh.it> <tCGvn-7oC-1@gated-at.bofh.it> <tCGYq-7Na-21@gated-at.bofh.it> <tCHB8-8eV-13@gated-at.bofh.it> <tCSPT-7i5-1@gated-at.bofh.it>
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  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 ...

Michael?  Ilia?

cheers,
  Gerd

Thread

[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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