Bug 12460

Summary:	[855GM backlight] Thinkpad X40 backlight turns off, won't turn on at keystroke
Product:	xorg	Reporter:	Norman Ramsey <nr>
Component:	Driver/intel	Assignee:	Jesse Barnes <jbarnes>
Status:	RESOLVED NOTOURBUG	QA Contact:	Xorg Project Team <xorg-team>
Severity:	minor
Priority:	medium
Version:	7.2 (2007.02)
Hardware:	x86 (IA32)
OS:	Linux (All)
URL:	http://tinyurl.com/2ewf4r
Whiteboard:
i915 platform:		i915 features:
Bug Depends on:
Bug Blocks:	13027

Description Norman Ramsey 2007-09-17 08:42:30 UTC

This bug is difficult to reproduce reliably.  I'm running Debian lenny/sid using xserver-xorg 1:7.2-5 with driver xserver-xorg-video-intel 2:2.1.0-2, and the X screen sometimes gets into a state where when the backlight is turned off (because I am using a USB keyboard and so no keyboard activity is registered), it does not come back on again at a keystroke.  BUT it is possible to restore the backlight by using Ctl-Alt-F1 to switch the console (at which point the backlight is turned on) and then 'chvt 7' to get back to the X screen, at which point the backlight stays on, for a while at least.

This state is extremely difficult to reproduce reliably, but once the system enters this state, it usually stays in it for some time---I may lose the backlight three or four times and have to switch consoles each time to get it back.  Then the system will transition back to a more normal state in which when the backlight drops out I can restore it just by pressing the shift key.

In case it's useful, the server is started by running startx (not as root) from the command line, not by a daemon like xdm or gdm.

In case it's helpful, the URL points to /var/log/Xorg.0.log.

I realize this bug is nearly impossible to reproduce and therefore is unlikely to be fixed, but if anybody has ideas, I would love someone to have a look.

Comment 1 Jesse Barnes 2007-10-31 15:54:26 UTC

Yeah, there are several potential problems with backlight control on Thinkpads.  Hopefully we can get it fixed for you.

Comment 2 Jesse Barnes 2007-11-12 13:27:21 UTC

Norman, can you try the latest Intel driver from git?  I just checked in some big backlight changes, including support for Thinkpads, so hopefully your problem is fixed now.

Thanks,
Jesse

Comment 3 Norman Ramsey 2007-11-12 20:49:56 UTC

(In reply to comment #2)
> Norman, can you try the latest Intel driver from git?  I just checked in some
> big backlight changes, including support for Thinkpads, so hopefully your
> problem is fixed now.

I'm compiling the new kernel now, but it appears that make-kpkg has issues with building kernels from git repositories, and it gets itself into an inconsistent state.  Unfortunately my pre-Debian kernel installation skills have atrophied completely :-(  I may have to report a bug against Debian kernel-package before I can proceed.

Comment 4 Jesse Barnes 2007-11-12 21:16:24 UTC

To test these fixes you should only have to rebuild the intel X driver, not the kernel.  Hopefully that'll make your life a little easier. :)

Comment 5 Jesse Barnes 2007-12-04 17:14:07 UTC

There's an updated backlight patch in 13306, can you try that?

Thanks,
Jesse

Comment 6 Jesse Barnes 2007-12-11 14:07:06 UTC

Given the behavior I'm pretty sure this isn't an Intel X driver bug (and if it was it should be fixed with the latest changes we've made to the backlight code).

It sounds like it might actually be a bug in the kernel's thinkpad driver or in a desktop utility that controls your display power saving.  Maybe they're missing events somehow?

So since the actual X server backlight control appears to work I'm going to close this out...  If you find some way of reproducing it reliably and it definitely looks like an X bug, please open a new one and we'll track it from there.

Thanks,
Jesse

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