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Re: Blank screen bug

On Sat, Sep 23, 2017 at 12:01:31PM +0200, Tim wrote:
> Hi,
> I would like to report a bug for Debian stretch, however, I'm not sure
> which package I should file the bug against. Moreover, I haven't found
> a way to debug the issue either.
> I've recently done a fresh installed of stretch on an HP EliteBook 840
> notebook. Since then, the laptop's screen sometimes turns blank, i.e.,
> as if there is no input to the screen. Strangely enough, whenever I
> attach another display, the other display doesn't go blank: It's only
> the internal display of the laptop itself that turns completely black.
> I've tried to debug the issue by looking a various log files (e.g.,
> ~/.local/share/xorg/Xorg.0.log, /var/log/kern.log, running
> `journalctl`), but nothing would show up in these logs whenever it
> occurs. I also tried to install `firmware-linux-nonfree` but that
> didn't help either. Before, I was using jessy without the bug.
> I hope you can tell me which package I should file the bug to, or how
> to proceed from here.
I had this exact same problem with Jessie on an HP ProBook 650.  The bug
was in X.org and was fixed when I upgraded to Stretch.  The problem, as
I recall, was that certain display hardware inverts the sense of the
intensity, so that instead of it going from 0 (dark) to max (bright) it
goes from 0 (bright) to max (dark).  X.org sets the display brightness
to what it thinks is max on the log in screen to compensate for the
possibility that was turned all the way down by a previous user.

What I found as a "workaround" was that I could log in as normal and
then by using the brightness control function keys I could increase the
display brightness after logging in.

I am not sure if the problem is that X.org needs to be told which
hardware inverts the meaning of the brightness control value, but I
suspect that is root cause.

I apologize that I don't have any links, but it has been several years
since I dealt with this problem.  Perhaps this is enough to get you
pointed in the right direction.



Roberto C. Sánchez

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