Updating with some questions from Kamal Mostafa and my answers: > In the report, please make a note of which backlight interfaces appear > when you run "ls /sys/class/backlight" when you do *not* boot with > acpi_backlight=vendor, and also when you *do*.
Without acpi_backlight=vendor: * acpi_video0 * intel_backlight With acpi_backlight=vendor: * dell_backlight * intel_backlight > Since you say that you can sometimes make it recover by switching to a > different console tty then back again, my guess is that the system is > probably actually always suspending and resuming correctly -- but the > backlight is sometimes not getting re-enabled on resume. If you have > another machine on your network, you could try to confirm that by > ping'ing or ssh'ing into the laptop while its in its dark state. In > fact, if you can ssh into it, we could then try checking the brightness > state and manually increasing it. Let me know what you find when you > try to ping or ssh into the machine and we'll proceed from there. When I can't get the display working, the laptop is responsive. I often have it hooked up to a second display through the HDMI port, and that display does enable properly. Getting the display back ON by switching ttys is rare, but doing a full system suspend and resume ALWAYS causes the display to be reenabled. * How can I manually induce a display suspend? * How do I manually change the display brightness level? > Now you also mention that closing and opening the lid again fixes the > problem... Is that behavior consistent? Specifically, are you saying > that it *always* fails to light up when you suspend/resume the first > time, but then *always* lights up again when you suspend/resume the > second time? Or is the behavior not as consistent as that? Correct, a full system suspend/resume always fixes the issue. -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/872652 Title: Display Hang With acpi_backlight=vendor To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/872652/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
