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Subject: Re: [PATCH 3/5] drm: fix drm_mode_addfb() on big endian machines.
To:     Gerd Hoffmann <kraxel@redhat.com>, David Airlie <airlied@linux.ie>,
        Sean Paul <sean@poorly.run>
References: <20180903105756.24912-1-kraxel@redhat.com>
 <20180903105756.24912-4-kraxel@redhat.com>
 <20180903164558.GL21634@phenom.ffwll.local>
Cc:     dri-devel@lists.freedesktop.org,
        open list <linux-kernel@vger.kernel.org>
From:   =?UTF-8?Q?Michel_D=c3=a4nzer?= <michel@daenzer.net>
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Date:   Mon, 3 Sep 2018 19:01:55 +0200
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On 2018-09-03 6:45 p.m., Daniel Vetter wrote:
> On Mon, Sep 03, 2018 at 12:57:54PM +0200, Gerd Hoffmann wrote:
>> Userspace on big endian machhines typically expects the ADDFB ioctl
>> returns a big endian framebuffer.  drm_mode_addfb() will call
>> drm_mode_addfb2() unconditionally with little endian DRM_FORMAT_*
>> values though, which is wrong.  This patch fixes that.
>>
>> Drivers (both kernel and xorg) have quirks in place to deal with the
>> broken drm_mode_addfb() behavior.  Because of this we can't just change
>> drm_mode_addfb() behavior for everybody without breaking things.  So add
>> a new driver feature flag DRIVER_PREFER_HOST_BYTE_ORDER, so drivers can
>> opt-in.

Since the changes are opt-in now, they shouldn't affect drivers which
don't opt in; they should work as well (or as badly :) after these
changes as they did before. So no concerns from my side anymore.


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