linux-kernel - HDMI/DVI unplug/plug kernel uevent

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Message-ID: <AANLkTim9Sz6o46Rxs=YX0=+5FwmrCr0=rtrOvLXJAH91@mail.gmail.com>
Date:	Wed, 22 Sep 2010 09:55:04 +1200
From:	Keith Chew <keith.chew@...il.com>
To:	linux-kernel <linux-kernel@...r.kernel.org>
Subject: HDMI/DVI unplug/plug kernel uevent

Hi

First, I apologise if this is not the correct mailing list to post my
question, it relates to both the kernel source and Xorg server. I will
re-post this to the Xorg mailing list if I cannot get an answer here.

I have a linux box which is connected to only one type of LCD. Using
Fedora 13, I am on:
- Xorg server 1.8.2
- kernel 2.6.33.2
- fluxbox with all services turned off (except crond, network), ie no
other userspace daemons

My problem is when I unplug and plug in the HDMI, I can see
/var/log/Xorg.0.log reprobing the LCD, and sometimes the screen goes
blank. I would like to disable this probe on the even of unplug/plug.

In drivers/gpu/drm/i915/i915_irq.c, there is this line:
-------------------
	/* Just fire off a uevent and let userspace tell us what to do */
	drm_sysfs_hotplug_event(dev);
-------------------

If I uncomment drm_sysfs_hotplug_event(), the uvent is not fired
(verified from udevadm --monitor) and no re-probing is done, perfect.
However, my real goal is to change the userspace app that is consuming
this uevent and not call the probe method. But I can't seem to find
out which app is consuming the uevent. I looked at the Xorg server's
sourcecode but cannot find see anykind of listener for this uevent (or
even a polling routine to check the drm sysfs status).

Can someone point me to the right direction please?

Regards
Keith
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