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

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Date:   Wed, 26 Apr 2017 11:00:09 +0900
From:   Michel Dänzer <michel@...nzer.net>
To:     Ville Syrjälä <ville.syrjala@...ux.intel.com>
Cc:     Daniel Vetter <daniel.vetter@...el.com>,
        dri-devel@...ts.freedesktop.org, Gerd Hoffmann <kraxel@...hat.com>,
        amd-gfx@...ts.freedesktop.org,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/6] drm: fourcc byteorder: add bigendian support to
 drm_mode_legacy_fb_format

On 25/04/17 06:52 PM, Ville Syrjälä wrote:
> On Tue, Apr 25, 2017 at 12:18:52PM +0900, Michel Dänzer wrote:
>> On 24/04/17 03:25 PM, Gerd Hoffmann wrote:
>>> +#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.
> 
> To 8bpp no, but it can easily apply to 24bpp.

Any byte swapping rips apart the bytes of a 24bpp pixel, so those
formats only make sense as straight array formats.


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