<html> <head> <base href="https://bugs.freedesktop.org/" /> </head> <body> <div> <a class="bz_bug_link bz_status_NEEDINFO " title="NEEDINFO - intel_backlight doesn't work with i915 Haswell" href="https://bugs.freedesktop.org/show_bug.cgi?id=92866#c12">Comment # 12</a> on <a class="bz_bug_link bz_status_NEEDINFO " title="NEEDINFO - intel_backlight doesn't work with i915 Haswell" href="https://bugs.freedesktop.org/show_bug.cgi?id=92866">bug 92866</a> from <a class="email" href="mailto:holgerschurig@gmail.com" title="Holger Schurig <holgerschurig@gmail.com>"> Holger Schurig</a> <pre>Jani, there is no dmesg output. I actually have two different systems with 8086:0a16 devices, one is running an i5-4300U and an Advantech BIOS, the other is running some slower CPU (forgot which one) on has a congatec BIOS (derived from AMI BIOS, I think). Both have the same issue with vbetool, it's just the 8086:a011 (also i915) that worked (and various device with even other graphics card). I'm writing this because both Haswell devices export different backlight directories in /sys. This is the congatec BIOS one: root@hwtester:/sys/class/backlight/acpi_video0# grep -d skip . * actual_brightness:0 bl_power:0 brightness:0 max_brightness:100 type:firmware When (still with drm.debug=14) I "echo 0 >bl_power" or when I run "echo 0 >brightness" ... * nothing visible changes on the display and * nothing new will be emitted to dmesg Aaaaaaand this is i915 with the Advantech BIOS: root@hwtester:/sys/class/backlight/intel_backlight# grep -d skip . * actual_brightness:937 bl_power:1 brightness:937 max_brightness:937 type:raw First, it exports a different backlight interfaces. But (still with drm.debug=14) I can "echo 0 >bl_power" and won't see anything at all in dmesg. But when I run "echo 1 >bl_power", I see this: [ 82.253378] [drm:intel_backlight_device_update_status] updating intel_backlight, brightness=937/937 [ 82.253381] [drm:intel_panel_actually_set_backlight] set backlight PWM = 937 [ 82.253388] [drm:intel_edp_backlight_power] panel power control backlight disable Only after this will "echo 0 >bl_power" emit this: [ 157.801385] [drm:intel_backlight_device_update_status] updating intel_backlight, brightness=937/937 [ 157.801388] [drm:intel_panel_actually_set_backlight] set backlight PWM = 937 [ 157.801395] [drm:intel_edp_backlight_power] panel power control backlight enable That is, the first "echo 0" was silent, the 2nd not. And visible is nothing, if I enable or disable anything. I also think that the dmesg output doesn't reflect the intent (despite from not working). I emits "disable" when I send a 1 (enable) and vica verca. Funny fact: the opaque OS called "Windows 10" can turn the backlight on and off on both i915 devices.</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> <li>You are the assignee for the bug.</li> </ul> </body> </html>