Screen brightness after screen lock

[dave0109]

I've been having an intermittent problem with the screen brightness on a Dell Latitude D620. Ordinarily the brightness is fine and I can control it with the keyboard function keys, without problem.

Then, sometimes after the screen has been locked and I've entered my password, the screen has minimal brightness and the function keys no longer do anything.

However, it's not everytime after the screen has been locked that the problem occurs.

I had it happen just recently and was able to "fix" it but opening Settings Manager -> Display and reversing the screen. I let it time-out so that it reverted back to normal and the full brightness returned as did the function keys.

[dave0109]

Anyone? This happened again today. Tis annoying.

[dave0109]

So within the Power Management settings, there's a brightness setting. If I set it low, the screen appears to go dimmer than with a higher value (but it never comes back to full brightness). So I tried setting it to 100%, but when I close the Power Management dialog and then go back to it, the value seems to max out at 80%. I even set the timeout to "never" dim the screen, but that appears to have no effect.

I tried running xfce4-power-manager in debug mode, but it doesn't log anything when the screen gets dimmed.

If I stop either xfce4-power-manager or xscreensaver then the screen is turned off after a delay and comes back dim. If I stop both of them, then the screen never goes off.

So something that is common to xfce4-power-manager and xscreensaver has a problem, but I don't know enough about the system to know what is shared by those programs.

Can someone with a clue jump in here please...

[markbl]

I have an old Dell 640m laptop which was having various problems with the brightness controls under ubuntu 11.10, problems which I did not see under 10.10. One of those problems was that my screen dimmed after screen lock. All those problems went away for me after I updated the bios in my laptop (from A04 to A10).

[dave0109]

Thanks, but although I've now upgraded the BIOS, it still doesn't help.

[Toz]

The next time the problem happens, have a look at ~/.xsession-errors - maybe some clues in there. Feel free to post the contents back.

Also, what directories do you have in /sys/class/backlight? I hava toshiba directory (because my laptop is a toshiba). In that directory, I have:


$ ls /sys/class/backlight/toshiba/
actual_brightness brightness max_brightness subsystem uevent
bl_power device power type


For whatever directory you have, it would be interesting to note what the value of the file actual_brightness is before and after the problem:

$ cat /sys/class/backlight/toshiba/actual_brightness
7


Also, you "should" be able to affect the brightness by echoing a value into the brightness file like:

echo 7 | sudo tee /sys/class/backlight/toshiba/brightness
...just make sure the value is between 0 and:

$ cat /sys/class/backlight/toshiba/max_brightness
7


Does echoing a value into the brightness file alter your brightness level?

Also, the results of this command might be helpful (to see what kernel parameters you are using):

cat /proc/cmdline

[dave0109]

Thanks, I have the value of 7 as well. Frustratingly, it hasn't gone wrong at all this evening.

[dave0109]

OK, very interesting results. I have two symlinks in the backlight directory...



/sys/class/backlight$ ls
dell_backlight intel_backlight


When things are working normally, i.e. after booting up, brightness is at my normal level and the Dell function keys work to control the brightness, then it is the data in the dell_backlight files that changes. So max_brightness is 7 and the value of brightness and actual_brightness goes up or down with the screen brightness as per my requests.

Then the power manager settings kicked in (which is currently set to switch off the screen after 2 minutes rather than the screensavers 15 minutes, but reduce brightness never). After wiggling the mouse I had a dark screen.

The settings in dell_backlight had not changed, but the ones in intel_backlight had. There max_brightness is 624, and the value of brightness and actual_brightness was 0. Echoing 624 into the brightness file restored the screen back to normal. Result. So thanks Toz, it's nice to be getting somewhere.

Question is, what now? And why do I have two links in backlight?

[dave0109]

Anyone? Toz?

I've not been able to work out why the dell directory is affected normally, but the intel one after the power-manager and/or screensaver kicks in.

[mobius129a]

What version of Ubuntu are you running?

[Toz]

OK, very interesting results. I have two symlinks in the backlight directory...



/sys/class/backlight$ ls
dell_backlight intel_backlight


When things are working normally, i.e. after booting up, brightness is at my normal level and the Dell function keys work to control the brightness, then it is the data in the dell_backlight files that changes. So max_brightness is 7 and the value of brightness and actual_brightness goes up or down with the screen brightness as per my requests.

Then the power manager settings kicked in (which is currently set to switch off the screen after 2 minutes rather than the screensavers 15 minutes, but reduce brightness never). After wiggling the mouse I had a dark screen.

The settings in dell_backlight had not changed, but the ones in intel_backlight had. There max_brightness is 624, and the value of brightness and actual_brightness was 0. Echoing 624 into the brightness file restored the screen back to normal. Result. So thanks Toz, it's nice to be getting somewhere.

Question is, what now? And why do I have two links in backlight?

When this happens, is anything logged to ~/.xsession-errors or /var/log/Xorg.0.log? What kind of video card do you have? Can you post back the contents of /var/log/Xorg.0.log and the results of:

lsmod
...and

cat /proc/cmdline

[dave0109]

@mobuis - Xubuntu 11.10

@Toz - nothing logged to ~/.xsession-errors nor /var/log/Xorg.0.log once the powermanager kicks in. The latter has the same repeating 3 lines:-



[ 32.469] (II) intel(0): EDID vendor "SEC", prod id 17495
[ 32.469] (II) intel(0): Printing DDC gathered Modelines:
[ 32.469] (II) intel(0): Modeline "1440x900"x0.0 95.44 1440 1504 1536 1744 900 903 906 912 -hsync -vsync (54.7 kHz)


I've an Intel 945GM Chipset integrated graphics on this laptop.



$ cat /proc/cmdline
BOOT_IMAGE=/boot/vmlinuz-3.0.0-13-generic root=UUID=cad3e6ac-1c74-4888-b06e-17fe18a448c3 ro quiet splash vt.handoff=7
$ lsmod
Module Size Used by
twofish_generic 16579 0
twofish_i586 12503 0
twofish_common 20823 2 twofish_generic,twofish_i586
xts 12644 0
gf128mul 14503 1 xts
dm_crypt 22565 0
snd_hrtimer 12648 1
bnep 17923 2
rfcomm 38408 4
pci_stub 12550 1
vboxpci 22882 0
vboxnetadp 13328 0
vboxnetflt 27211 0
vboxdrv 251814 3 vboxpci,vboxnetadp,vboxnetflt
parport_pc 32114 0
ppdev 12849 0
binfmt_misc 17292 1
firewire_ohci 35854 0
firewire_core 56937 1 firewire_ohci
crc_itu_t 12627 1 firewire_core
snd_hda_codec_idt 60049 1
joydev 17393 0
btusb 18160 0
bluetooth 148839 11 bnep,rfcomm,btusb
usbhid 41905 0
hid 77367 1 usbhid
dell_wmi 12601 0
sparse_keymap 13658 1 dell_wmi
dell_laptop 13519 0
dcdbas 14098 1 dell_laptop
pcmcia 39822 0
arc4 12473 2
psmouse 73673 0
snd_hda_intel 24262 3
snd_hda_codec 91754 2 snd_hda_codec_idt,snd_hda_intel
snd_hwdep 13276 1 snd_hda_codec
snd_pcm 80468 2 snd_hda_intel,snd_hda_codec
snd_seq_midi 13132 0
snd_rawmidi 25241 1 snd_seq_midi
serio_raw 12990 0
snd_seq_midi_event 14475 1 snd_seq_midi
yenta_socket 27428 0
pcmcia_rsrc 18367 1 yenta_socket
pcmcia_core 21511 3 pcmcia,yenta_socket,pcmcia_rsrc
b43 318816 0
i915 505108 2
snd_seq 51567 3 snd_seq_midi,snd_seq_midi_event
mac80211 393459 1 b43
snd_timer 28932 3 snd_hrtimer,snd_pcm,snd_seq
snd_seq_device 14172 3 snd_seq_midi,snd_rawmidi,snd_seq
drm_kms_helper 32889 1 i915
drm 192226 3 i915,drm_kms_helper
cfg80211 172392 2 b43,mac80211
snd 55902 16 snd_hda_codec_idt,snd_hda_intel,snd_hda_codec,snd_ hwdep,snd_pcm,snd_rawmidi,snd_seq,snd_timer,snd_se q_device
wmi 18744 1 dell_wmi
i2c_algo_bit 13199 1 i915
soundcore 12600 1 snd
video 18908 1 i915
coretemp 13188 0
snd_page_alloc 14115 2 snd_hda_intel,snd_pcm
lp 17455 0
parport 40930 3 parport_pc,ppdev,lp
tg3 132972 0
ssb 50682 1 b43

[Toz]

What happens if you boot with the kernel parameter acpi_backlight=vendor? Try a test using the instructions at: https://help.ubuntu.com/community/Grub2#Editing_the_GRUB_2_Menu_During_Boot

[dave0109]

That didn't appear to have an effect. Hoping I added the parameter in the right place. It's not something I've done before. Thanks for sticking with me. :)



$ cat /proc/cmdline
BOOT_IMAGE=/boot/vmlinuz-3.0.0-13-generic root=UUID=cad3e6ac-1c74-4888-b06e-17fe18a448c3 ro quiet splash vt.handoff=7 acpi_backlight=vendor
$ lsmod
Module Size Used by
snd_hrtimer 12648 1
bnep 17923 2
rfcomm 38408 12
pci_stub 12550 1
vboxpci 22882 0
vboxnetadp 13328 0
vboxnetflt 27211 0
vboxdrv 251814 3 vboxpci,vboxnetadp,vboxnetflt
parport_pc 32114 0
ppdev 12849 0
binfmt_misc 17292 1
firewire_ohci 35854 0
firewire_core 56937 1 firewire_ohci
crc_itu_t 12627 1 firewire_core
snd_hda_codec_idt 60049 1
joydev 17393 0
usbhid 41905 0
hid 77367 1 usbhid
snd_hda_intel 24262 3
snd_hda_codec 91754 2 snd_hda_codec_idt,snd_hda_intel
snd_hwdep 13276 1 snd_hda_codec
btusb 18160 2
snd_pcm 80468 2 snd_hda_intel,snd_hda_codec
bluetooth 148839 23 bnep,rfcomm,btusb
dell_wmi 12601 0
sparse_keymap 13658 1 dell_wmi
snd_seq_midi 13132 0
dell_laptop 13519 0
dcdbas 14098 1 dell_laptop
pcmcia 39822 0
snd_rawmidi 25241 1 snd_seq_midi
arc4 12473 2
snd_seq_midi_event 14475 1 snd_seq_midi
snd_seq 51567 3 snd_seq_midi,snd_seq_midi_event
psmouse 73673 0
snd_timer 28932 3 snd_hrtimer,snd_pcm,snd_seq
b43 318816 0
serio_raw 12990 0
yenta_socket 27428 0
pcmcia_rsrc 18367 1 yenta_socket
pcmcia_core 21511 3 pcmcia,yenta_socket,pcmcia_rsrc
snd_seq_device 14172 3 snd_seq_midi,snd_rawmidi,snd_seq
mac80211 393459 1 b43
snd 55902 16 snd_hda_codec_idt,snd_hda_intel,snd_hda_codec,snd_ hwdep,snd_pcm,snd_rawmidi,snd_seq,snd_timer,snd_se q_device
wmi 18744 1 dell_wmi
i915 505108 2
cfg80211 172392 2 b43,mac80211
drm_kms_helper 32889 1 i915
drm 192226 3 i915,drm_kms_helper
soundcore 12600 1 snd
snd_page_alloc 14115 2 snd_hda_intel,snd_pcm
i2c_algo_bit 13199 1 i915
video 18908 1 i915
coretemp 13188 0
lp 17455 0
parport 40930 3 parport_pc,ppdev,lp
tg3 132972 0
ssb 50682 1 b43

[dave0109]

There appears to be a small difference, in that now, the power manager doesn't appear to kick in. I have in the 'On AC' -> Monitor settings:-

Put display to sleep: Never
Switch off display when inactive: 1 minute (good for testing)
Reduce screen brightness: Never

Previously, this would kick in after 1 minute and then not come back at full brightness.

Now, with the kernel boot param, it's not kicking in, and it's the screen saver that's blanking the screen after 5 mins (as set in the screensaver settings).

[Toz]

That didn't appear to have an effect. Hoping I added the parameter in the right place. It's not something I've done before. Thanks for sticking with me. :)



$ cat /proc/cmdline
BOOT_IMAGE=/boot/vmlinuz-3.0.0-13-generic root=UUID=cad3e6ac-1c74-4888-b06e-17fe18a448c3 ro quiet splash vt.handoff=7 acpi_backlight=vendor
$ lsmod
Module Size Used by
snd_hrtimer 12648 1
bnep 17923 2
rfcomm 38408 12
pci_stub 12550 1
vboxpci 22882 0
vboxnetadp 13328 0
vboxnetflt 27211 0
vboxdrv 251814 3 vboxpci,vboxnetadp,vboxnetflt
parport_pc 32114 0
ppdev 12849 0
binfmt_misc 17292 1
firewire_ohci 35854 0
firewire_core 56937 1 firewire_ohci
crc_itu_t 12627 1 firewire_core
snd_hda_codec_idt 60049 1
joydev 17393 0
usbhid 41905 0
hid 77367 1 usbhid
snd_hda_intel 24262 3
snd_hda_codec 91754 2 snd_hda_codec_idt,snd_hda_intel
snd_hwdep 13276 1 snd_hda_codec
btusb 18160 2
snd_pcm 80468 2 snd_hda_intel,snd_hda_codec
bluetooth 148839 23 bnep,rfcomm,btusb
dell_wmi 12601 0
sparse_keymap 13658 1 dell_wmi
snd_seq_midi 13132 0
dell_laptop 13519 0
dcdbas 14098 1 dell_laptop
pcmcia 39822 0
snd_rawmidi 25241 1 snd_seq_midi
arc4 12473 2
snd_seq_midi_event 14475 1 snd_seq_midi
snd_seq 51567 3 snd_seq_midi,snd_seq_midi_event
psmouse 73673 0
snd_timer 28932 3 snd_hrtimer,snd_pcm,snd_seq
b43 318816 0
serio_raw 12990 0
yenta_socket 27428 0
pcmcia_rsrc 18367 1 yenta_socket
pcmcia_core 21511 3 pcmcia,yenta_socket,pcmcia_rsrc
snd_seq_device 14172 3 snd_seq_midi,snd_rawmidi,snd_seq
mac80211 393459 1 b43
snd 55902 16 snd_hda_codec_idt,snd_hda_intel,snd_hda_codec,snd_ hwdep,snd_pcm,snd_rawmidi,snd_seq,snd_timer,snd_se q_device
wmi 18744 1 dell_wmi
i915 505108 2
cfg80211 172392 2 b43,mac80211
drm_kms_helper 32889 1 i915
drm 192226 3 i915,drm_kms_helper
soundcore 12600 1 snd
snd_page_alloc 14115 2 snd_hda_intel,snd_pcm
i2c_algo_bit 13199 1 i915
video 18908 1 i915
coretemp 13188 0
lp 17455 0
parport 40930 3 parport_pc,ppdev,lp
tg3 132972 0
ssb 50682 1 b43


After you've booted with the acpi_backlight=vendor kernel parameter, post back the results of:

cat /proc/cmdline
...and

ls /sys/class/backlight
...and

ls /proc/acpi

[Toz]

There appears to be a small difference, in that now, the power manager doesn't appear to kick in. I have in the 'On AC' -> Monitor settings:-

Put display to sleep: Never
Switch off display when inactive: 1 minute (good for testing)
Reduce screen brightness: Never

Previously, this would kick in after 1 minute and then not come back at full brightness.

Now, with the kernel boot param, it's not kicking in, and it's the screen saver that's blanking the screen after 5 mins (as set in the screensaver settings).

Is the power manager daemon working?

ps -ef | grep power-manager | grep -v grep

[dave0109]

cat /proc/cmdline
BOOT_IMAGE=/boot/vmlinuz-3.0.0-13-generic root=UUID=cad3e6ac-1c74-4888-b06e-17fe18a448c3 ro quiet splash vt.handoff=7 acpi_backlight=vendor

...and

ls /sys/class/backlight
dell_backlight intel_backlight

...and

ls /proc/acpi
ac_adapter battery button event wakeup

> Is the power manager daemon working?
Yeah, it's running.

[Toz]

For some reason you have 2 backlight interfaces and I'm guessing that when you are coming out of screensaver mode, the system is switching between the two. Unfortunately I don't know why.

What happens if you:

sudo modprobe -r dell_laptop

If its successful, also check your laptop function keys to see if they still work.

[dave0109]

OK, that has resulted in the removal of dell_backlight from /sys/class/backlight, but it's had no effect. When power-manager kicks in, blanks the screen and I bring it back, the brightness is still dim.

I'll try booting with the kernel option and then do the module removal too.... which made no difference. :(

[dave0109]

Looks like a bug in the kernel for the intel 915 driver, which has now been patched and made its way into the next kernel update 3.0.0-14. Gonna wait for this to get released and see if it fixes the issue. Should help all the others out there too, no matter which flavour of Ubuntu.

https://bugs.launchpad.net/ubuntu/+source/linux/+bug/872652

[dave0109]

Finally solved with kernel 3.0.0-15-generic. Number 14 didn't do it on my system, but 15 has, without needing any additional boot parameters.