linux-kernel - Re: [PATCH 3/6] drm: fourcc byteorder: add bigendian support to drm_mode_legacy_fb

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Date:   Tue, 25 Apr 2017 12:18:52 +0900
From:   Michel Dänzer <michel@...nzer.net>
To:     Gerd Hoffmann <kraxel@...hat.com>
Cc:     dri-devel@...ts.freedesktop.org,
        open list <linux-kernel@...r.kernel.org>,
        amd-gfx@...ts.freedesktop.org,
        Daniel Vetter <daniel.vetter@...el.com>
Subject: Re: [PATCH 3/6] drm: fourcc byteorder: add bigendian support to
 drm_mode_legacy_fb_format

On 24/04/17 03:25 PM, Gerd Hoffmann wrote:
> Return correct fourcc codes on bigendian.  Drivers must be adapted to
> this change.
> 
> Signed-off-by: Gerd Hoffmann <kraxel@...hat.com>

Just to reiterate, this won't work for the radeon driver, which programs
the GPU to use (effectively, per the current definition that these are
little endian GPU formats) DRM_FORMAT_XRGB8888 with pre-R600 and
DRM_FORMAT_BGRX8888 with >= R600.


> +#ifdef __BIG_ENDIAN
> +	switch (bpp) {
> +	case 8:
> +		fmt = DRM_FORMAT_C8;
> +		break;
> +	case 24:
> +		fmt = DRM_FORMAT_BGR888;
> +		break;

BTW, endianness as a concept cannot apply to 8 or 24 bpp formats.


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