dell-laptop: Incorrect keyboard backlight detection

[Darek Stojaczyk]

I own Dell Inspiron M5110 (Q15R). This laptop has no keyboard backlight, but dell-laptop claims otherwise.
My syslog was getting spammed with "Keyboard brightness level control not supported" as dell-laptop was trying to get/set backlight values.

In dell-laptop there is kbd_led_present variable, but on my M5110 it's being set to true:

 ret = kbd_init_info();
 (...)
 if (kbd_token_bits != 0 || ret == 0)
  kbd_led_present = true;

kbd_token_bits is 0, but so is ret.
kbd_init_info method is only returning != 0 if kbd_get_info is returning != 0

(Basing on this: http://linux.dell.com/cgi-bin/cgit.cgi/libsmbios.git/tree/src/bin/smbios-keyboard-ctl#n667)
kbd_get_info method returns only cbRES1 value of following smbios call :
cbClass 4
cbSelect 11
cbArg1 0x0
And it returns 0...
I found that any cbRES of this call is giving me nothing but zeros, as if it wasn't defined in my BIOS. I have it's newest version for my laptop:
[ 0.000000] SMBIOS 2.7 present.
[ 0.000000] DMI: Dell Inc. Inspiron M5110/0X7W03, BIOS A05 03/22/2012

However, if "cbRES3, byte2 Number of keyboard light brightness levels" is 0 as well, that should mean backlight is not available, right? I'm attaching possible fix.

[Brad Figg (brad-figg)]

This bug is missing log files that will aid in diagnosing the problem. From a terminal window please run:

apport-collect 1478696

and then change the status of the bug to 'Confirmed'.

If, due to the nature of the issue you have encountered, you are unable to run this command, please add a comment stating that fact and change the bug status to 'Confirmed'.

This change has been made by an automated script, maintained by the Ubuntu Kernel Team.

[Darek Stojaczyk (darsto)]

I believe all necessary logs are included in bug description.

[Joseph Salisbury (jsalisbury)]

Would it be possible for you to test the latest upstream kernel? Refer to https://wiki.ubuntu.com/KernelMainlineBuilds . Please test the latest v4.2 kernel[0].

If this bug is fixed in the mainline kernel, please add the following tag 'kernel-fixed-upstream'.

If the mainline kernel does not fix this bug, please add the tag: 'kernel-bug-exists-upstream'.

Once testing of the upstream kernel is complete, please mark this bug as "Confirmed".

Thanks in advance.

[0] http://kernel.ubuntu.com/~kernel-ppa/mainline/v4.2-rc4-unstable/

[Joseph Salisbury (jsalisbury)]

This issue appears to be an upstream bug, since you tested the latest upstream kernel. Would it be possible for you to open an upstream bug report[0]? That will allow the upstream Developers to examine the issue, and may provide a quicker resolution to the bug.

Please follow the instructions on the wiki page[0]. The first step is to email the appropriate mailing list. If no response is received, then a bug may be opened on bugzilla.kernel.org.

Once this bug is reported upstream, please add the tag: 'kernel-bug-reported-upstream'.

[0] https://wiki.ubuntu.com/Bugs/Upstream/kernel

[Henry J. Douglas (cyberdoug42-deactivatedaccount)]

I'm seeing my logs spammed with "dell_laptop: Keyboard brightness level control not supported" too. Have you reported the bug upstream already?

[Darek Stojaczyk (darsto)]

@Henry, No, I haven't. I don't have the Dell Inspiron M5110 laptop anymore and I can't reproduce this error. You can feel free to open the upstream bug report.

[mathew thomas (maxie)]

Um hello! Is anybody home?
Has there been any progress on this bug?
Is there a way to find out?
Ah! Because it's happening now on my inspiron n4050!

[Kai-Heng Feng (kaihengfeng)]

I guess this commit solves the issue:
1b1ffc57a1b2 platform/x86: dell-laptop: Fix bogus keyboard backlight sysfs interface

Latest mainline kernel (v4.13-rc5) has this commit. Give it a try.