linux-kernel - Re: [PATCH 3/5] drm: fix drm_mode

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Date:   Mon, 3 Sep 2018 19:01:55 +0200
From:   Michel Dänzer <michel@...nzer.net>
To:     Gerd Hoffmann <kraxel@...hat.com>, David Airlie <airlied@...ux.ie>,
        Sean Paul <sean@...rly.run>
Cc:     dri-devel@...ts.freedesktop.org,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/5] drm: fix drm_mode_addfb() on big endian machines.

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