<html> <head> <base href="https://bugs.freedesktop.org/" /> </head> <body> <div> <a class="bz_bug_link bz_status_RESOLVED bz_closed" title="RESOLVED NOTABUG - [regression] Backlight too dim to use from kernel 3.14 and systemd error" href="https://bugs.freedesktop.org/show_bug.cgi?id=78200#c19">Comment # 19</a> on <a class="bz_bug_link bz_status_RESOLVED bz_closed" title="RESOLVED NOTABUG - [regression] Backlight too dim to use from kernel 3.14 and systemd error" href="https://bugs.freedesktop.org/show_bug.cgi?id=78200">bug 78200</a> from <a class="email" href="mailto:jani.nikula@intel.com" title="Jani Nikula <jani.nikula@intel.com>"> Jani Nikula</a> <pre>(In reply to <a href="show_bug.cgi?id=78200#c18">comment #18</a>) > Therefore there is no kernel or systemd bug, and I will close this report as > resolved. > > The problem that led to my confusion was that at some point a kernel update > changed the max_brightness value from the driver for my system This is likely because of the fix commit b6ab66aa5d376583a17137cbb2d3a728f29acae2 Author: Jani Nikula <<a href="mailto:jani.nikula@intel.com">jani.nikula@intel.com</a>> Date: Tue Feb 25 13:11:47 2014 +0200 drm/i915: use backlight legacy combination mode also for i915gm/i945gm which would have that effect, and it matches your platform. I think you trying different kernel versions with and without that patch lead to systemd saving and then using out of range saved brightness value on 3.13. I think it's a bug in systemd, while it's not the root cause here. I sent a bug report in the disguise of a patch to systemd [1] to fix this: <a href="http://mid.gmane.org/1399453261-31967-1-git-send-email-jani.nikula@intel.com">http://mid.gmane.org/1399453261-31967-1-git-send-email-jani.nikula@intel.com</a> > However using the Fn + Up > Arrow keys did not reset the value in > /sys/class/backlight/intel_backlight/brightness despite the screen becoming > normal brightness, and so this low value persisted when systemd saved the > current value and restored it at next boot. This is probably due to ACPI handling the keys. Depending on the BIOS on your system, it's possible we sync that to the intel_backlight brightness too in recent kernels. > Sorry it took me so long to recognise that it was my kde script that was > causing the symptoms. No worries. Thanks for following up, and I'm glad you figured it out.</pre> </div> <hr> You are receiving this mail because: <ul> <li>You are the QA Contact for the bug.</li> <li>You are on the CC list for the bug.</li> </ul> </body> </html>