linux-kernel - Re: [RFC PATCH 3/5] drm/i915: register LVDS connector even if we can't get a panel mode

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Date:	Mon, 6 Aug 2012 07:44:16 +1000
From:	Dave Airlie <airlied@...il.com>
To:	Matthew Garrett <mjg59@...f.ucam.org>,
	dri-devel@...ts.freedesktop.org, David Airlie <airlied@...ux.ie>,
	linux-kernel@...r.kernel.org, Andreas Heider <andreas@...tr.de>
Subject: Re: [RFC PATCH 3/5] drm/i915: register LVDS connector even if we
 can't get a panel mode

On Mon, Aug 6, 2012 at 7:40 AM, Daniel Vetter <daniel@...ll.ch> wrote:
> On Sun, Aug 05, 2012 at 10:18:38PM +0100, Matthew Garrett wrote:
>> On Sun, Aug 05, 2012 at 11:14:12PM +0200, Daniel Vetter wrote:
>>
>> > I like this approach more - the only other solution I see is to ask the
>> > currently active driver (i.e. radeon) at bootime for the right mode. Which
>> > sounds much more hellish and fragile ...
>>
>> The "correct" approach is clearly to just have the drm core change the
>> i2c mux before requesting edid, but that's made difficult because of the
>> absence of ordering guarantees in initialisation. I don't like quirking
>> this, since we're then back to the situation of potentially having to
>> add every new piece of related hardware to the quirk list.
>
> The "correct" approach of switching the mux before we fetch the edid is
> actualy the one I fear will result in fragile code: Only run on few
> machines, and as you say with tons of funky interactions with the init
> sequence ordering. And I guess people will bitch&moan about the flickering
> this will cause ;-)
>
> As long as it's only apple shipping multi-gpu machines with
> broken/non-existing vbt, I'll happily stomach the quirk list entries.
> They're bad, but imo the lesser evil.

Well in theory you can switch the ddc lines without switching the other lines,
so we could do a mutex protected mux switch around edid retrival,

Of course someone would have to code it up first then we could see how
ugly it would be.

Dave.
> -Daniel
> --
> Daniel Vetter
> Mail: daniel@...ll.ch
> Mobile: +41 (0)79 365 57 48
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