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

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Message-ID: <20220712083157.wtujadjcyboerxcl@sirius.home.kraxel.org>
Date:   Tue, 12 Jul 2022 10:31:57 +0200
From:   Gerd Hoffmann <kraxel@...hat.com>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     Linux Fbdev development list <linux-fbdev@...r.kernel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Michel Dänzer <michel.daenzer@...lbox.org>,
        David Airlie <airlied@...ux.ie>,
        Linux/m68k <linux-m68k@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Noralf Trønnes <noralf@...nnes.org>,
        DRI Development <dri-devel@...ts.freedesktop.org>
Subject: Re: [PATCH 1/3] drm/fourcc: Add missing big-endian XRGB1555 and
 RGB565 formats

  Hi,

> So adding support for bigendian formats to the driver shouldn't be
> much of a problem.  The vram will continue to run in little endian
> RGB565, the shadow will be big endian RGB565, and the driver must
> byteswap when copying.

For completeness: The other obvious option (for fbcon) would be to
handle the byteswapping in the generic drm fbdev emulation, which
would have the advantage that it would be more generic and would
not depend on the drm driver supporting the bigendian rgb565
formats ...

take care,
  Gerd