linux-kernel - Re: [PATCH 0/4] drm/atmel-hlcdc: fix plane clipping/rotation issues

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Date:   Thu, 10 Jan 2019 21:24:02 +0000
From:   Peter Rosin <peda@...ntia.se>
To:     Boris Brezillon <bbrezillon@...nel.org>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        David Airlie <airlied@...ux.ie>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        Boris Brezillon <boris.brezillon@...tlin.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        Nicolas Ferre <nicolas.ferre@...rochip.com>
Subject: Re: [PATCH 0/4] drm/atmel-hlcdc: fix plane clipping/rotation issues

On 2019-01-10 18:45, Boris Brezillon wrote:
> On Thu, 10 Jan 2019 15:10:28 +0000
> Peter Rosin <peda@...ntia.se> wrote:
> 
>> Hi!
>>
>> I found an unfortunate issue while recoding plane handling to use
>> drm_atomic_helper_check_plane_state(). The driver rotates clockwise,
>> which is not correct. I simply fixed it (patch 1/4), but maybe that
>> will cause regressions for unsuspecting users who simply assumed
>> that the clockwise rotation was correct? I don't know what to do
>> about that? Adding an option to get the old broken behavior seems
>> useless, wouldn't it be just as easy to just fix whatever app to
>> rotate the other way instead of adding an option somewhere?
> 
> Hm, rotation support has been added before the standard rotation
> property was created, and at that time I assumed rotation was clockwise
> (which apparently was an unwise choice). Anyway, I don't have a
> solution for this problem, so I'll let Nicolas decide if it's
> acceptable to change the rotation behavior.

Speaking of unwise, fbcon rotation is clockwise and drm rotation
is counterclockwise. 'nuff said.

Cheers,
Peter