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Re: Blank screen bug

On Sat 23 Sep 2017 at 10:49:44 (-0400), Cindy-Sue Causey wrote:
> On 9/23/17, Roberto C. Sánchez <roberto@debian.org> wrote:
> > 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.
> Based on both of your posts, I took a quick peek at "apt-listbugs list
> -s all xorg"..
> #778573 xorg: Xorg shows blank black screen at startup instead of a
> Display Manager.
> https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=778573
> That references....
> #775012 nvidia-driver: startx initializes nvidia driver but kdm does not
> https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=775012
> May not be exact same thing, especially since they're speaking of boot
> and this thread sounds like it snaps off mid successful usage.

In the case of a laptop that has symptoms that were similar but
are now worse, I suspect a firmware problem, the reason being
that it now usually blanks even before the POST has finished.
But the screen is not black, just very dark. In X, white backgrounds
can just be detected.

> But
> maybe you all have come up with something no one thought of or
> possibly even knew was possible.... or not. You never know. :)
> Me? Never would have thought about manufacturers reversing how things
> work. That's a very not user friendly twist on proprietary....... :)

Well try this for size. Our washing machine that we inherited in 2014
had its hot/cold hoses connected backwards, but worked fine like that.
When we moved, I replumbed it, and wrote H and C on the back by
the hose attachments (contradicting the manufacturer's engravings).

Yesterday, all was normal with the sheets. Today, I noticed the
machine was filling cold water onto the towels. After checking
that we had hot water in the sink, I discovered that the machine's
Cold/Cool/Warm/Hot switch was working, but now in the reverse
direction. So I washed the towels in hot water by setting it on Cold.
When it got to the rinses, I _had_ to pull it out and swap the hoses
round because, of course, it was going to do all the rinsing with
hot water.

I have no idea how it decided to spontaneously switch the hot and
cold feeds after three years. With the hoses as per the original
markings, it's now working perfectly again. But can I trust it?


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