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Re: Blank screen bug

On Sat, Sep 23, 2017 at 7:48 AM, Roberto C. Sánchez <roberto@debian.org> wrote:
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.

Just confirming that apparently I had this same issue with jessie 8.4 on Dell hardware.
The problem only occurred if a second monitor was connected prior to boot. Only the
second monitor's brightness was dialed-up at boot, the primary (laptop) screen would
be dialed down to 0 brightness. Unfortunately the login prompt was on the laptop screen.
Simply dialing-up the brightness was the fix, but it took me a while to realize it.


Roberto C. Sánchez

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