[Intel-gfx] Unexpected behaviour of xrandr and the Intel driver on monitor hotplug

[Adam Jackson]

On Mon, 2010-05-17 at 12:13 +0100, Simon Farnsworth wrote:

> The first bit of misbehaviour I'm seeing is caching of EDID across hotplug
> events. If I boot my system with no display attached, I correctly see no EDID
> property. When I connect a monitor via VGA, using cabling that supports DDC, I
> see EDID. When I unplug the monitor, I continue to see the old EDID. When I
> then plug in using a cable that doesn't support DDC, I see an extra mode
> appear in the mode list, but the EDID has not changed. Connecting using the
> original cable, or disconnecting cables completely removes this extra mode.

commit 725398322d05486109375fbb85c3404108881e17
Author: Zhao Yakui <yakui.zhao at intel.com>
Date:   Thu Mar 4 08:25:55 2010 +0000

    drm: remove the EDID blob stored in the EDID property when it is disconnected
    
    Now the EDID property will be updated when the corresponding EDID can be
    obtained from the external display device. But after the external device
    is plugged-out, the EDID property is not updated. In such case we still
    get the corresponding EDID property although it is already detected as
    disconnected.
    
    https://bugs.freedesktop.org/show_bug.cgi?id=26743
    
    Signed-off-by: Zhao Yakui <yakui.zhao at intel.com>
    Signed-off-by: Zhenyu Wang <zhenyuw at linux.intel.com>
    Cc: stable at kernel.org
    Signed-off-by: Dave Airlie <airlied at redhat.com>

> The second misbehaviour I'm seeing is that the list of modes isn't predictable
> in the presence of hotplug. If I boot without EDID available, I get one list
> of modes; if I make EDID available by changing cables, I get a second list of
> modes. If I then change cables back to the no EDID cable, I get a third list
> of modes - I was expecting the first list again.

Probably a side effect of the above.

- ajax
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