There are no files in the /sys/class/backlight directory and no apparent way to set the backlight for the Dell Chrombook 11. Another user posted a detailed summary here: http://askubuntu.com/questions/577539/dell-chromebook-11-unable-to-set-backlight-and-sys-class-backlight-folder-is I couldn't find a bug report here, so I added one myself.
Please add drm.debug=14 module parameter and attach dmesg all the way from boot. Please also attach /sys/kernel/debug/dri/0/i915_opregion.
Created attachment 167441 [details] Dmesg output with drm.debug=14 Dmesg output from Dell Chromebook 11 with drm.debug=14 kernel parameter
"/sys/kernel/debug/dri/0/i915_opregion" is empty. Sorry for two comments.
(In reply to Owen Garland from comment #3) > "/sys/kernel/debug/dri/0/i915_opregion" is empty. Sorry for two comments. It's a special file, ls -l would report its size to be 0. Did you try to copy it?
Okay, the chromebook may need a quirk to enable backlight, *sigh*. Where do you infer that "screen detected as CRT"? What does xrandr say?
Also please provide output of 'lspci -vmmnn -s 0:02'.
Created attachment 167451 [details] xrandr --verbose output (In reply to Jani Nikula from comment #4) > (In reply to Owen Garland from comment #3) > > "/sys/kernel/debug/dri/0/i915_opregion" is empty. Sorry for two comments. > > It's a special file, ls -l would report its size to be 0. Did you try to > copy it? I tried to cat it, the file is definitely empty ls -l confirms this. (In reply to Jani Nikula from comment #5) > Okay, the chromebook may need a quirk to enable backlight, *sigh*. > > Where do you infer that "screen detected as CRT"? What does xrandr say? I've attached xrandr.txt that contains the output of xrandr --verbose, I think that is where I got the notion that it is a CRT.
Created attachment 167461 [details] lspci -vmmnn -s 0:02 output Added lspci output.
Created attachment 167481 [details] drm/i915: Dell Chromebook 11 has pwm backlight Please try this patch.
That did the trick. Thank you so much, hopefully one day I can fix things myself!
Fixed by commit cf6f0af9fbdd90b81af14fa6375387131cd8adf1 Author: Jani Nikula <jani.nikula@intel.com> Date: Thu Feb 19 10:53:39 2015 +0200 drm/i915: Dell Chromebook 11 has PWM backlight in drm-intel-fixes. Thanks for the report and testing.
Comment on attachment 167481 [details] drm/i915: Dell Chromebook 11 has pwm backlight >From cbaeb2136f02fb87ec89c1bf947d0114d2326c80 Mon Sep 17 00:00:00 2001 >From: Jani Nikula <jani.nikula@intel.com> >Date: Wed, 18 Feb 2015 18:15:56 +0200 >Subject: [PATCH] drm/i915: Dell Chromebook 11 has pwm backlight >Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo >Cc: Jani Nikula <jani.nikula@intel.com> > >Add quirk for Dell Chromebook 11 backlight. > >Signed-off-by: Jani Nikula <jani.nikula@intel.com> >--- > drivers/gpu/drm/i915/intel_display.c | 3 +++ > 1 file changed, 3 insertions(+) > >diff --git a/drivers/gpu/drm/i915/intel_display.c >b/drivers/gpu/drm/i915/intel_display.c >index 3b0fe9f1f3c9..d630ce46298a 100644 >--- a/drivers/gpu/drm/i915/intel_display.c >+++ b/drivers/gpu/drm/i915/intel_display.c >@@ -13100,6 +13100,9 @@ static struct intel_quirk intel_quirks[] = { > > /* HP Chromebook 14 (Celeron 2955U) */ > { 0x0a06, 0x103c, 0x21ed, quirk_backlight_present }, >+ >+ /* Dell Chromebook 11 */ >+ { 0x0a06, 0x1028, 0x0a35, quirk_backlight_present }, > }; > > static void intel_init_quirks(struct drm_device *dev) >-- >2.1.4 >