Backlight class isn't present

[Scampada]

Hi,

I was trying to find something in /sys/class/backlight to be able to change my screen brightness from CLI... But there is nothing. I put a boot laptop option, still no effect. Why? Is it something I have to tune inside my TC?

[Scampada]

Output from modprobe -l | grep backlight shows:

kernel/drivers/video/backlight/generic_bl.ko.gz
kernel/drivers/video/backlight/lcd.ko.gz
kernel/drivers/video/backlight/bd6107.ko.gz
kernel/drivers/video/backlight/adp8860_bl.ko.gz
kernel/drivers/video/backlight/backlight.ko.gz
kernel/drivers/video/backlight/platform_lcd.ko.gz
kernel/drivers/video/backlight/adp8870_bl.ko.gz
kernel/drivers/video/backlight/kb3886_bl.ko.gz
kernel/drivers/video/backlight/apple_bl.ko.gz

Looks like I have even unnecessary ones but there is only an empty /sys/class/backlight directory.

[curaga]

Are you sure your hardware can do that? Anything there on another distro?

[Scampada]

Yeah, sure. It's all OK under openSUSE, even brightness buttons are working fine. I found that in openSUSE there are two or three more kernel modules in
/lib/modules/$(uname -r)/kernel/drivers/video/backlight - gpio_backlight & pwm.bl. But it's not able to just copy them to TC, though. A pity.

What can I do?

My board is a netbook of 'Packard Bell dot s' series
http://www.ferra.ru/images/265/265157.jpg

[Scampada]

I can upgrade and rebuild the kernel, but... but... ohshi~

Are there TC 3.17.* kernel sources available? Does it depend strictly whether it's a TC kernel source or not? Can I manually compose a new TC compatible kernel source and build it?

[Scampada]

Btw. When I close the notebook its display goes pitch black. Does it mean it works with backlight somehow, then?
Also, if I do not touch it for some time, the display also goes black until key pressed. Does it mean the same?..

Well, how could it ever draw something on the screen if it didn't work with backlight hardware?

lsmod | grep light:
backlight 12288 2 acer_wmi,video

It is used by video module, how could it all work fine if it was not even recognized?

I had also found something about backlight in /sys/module, but I'm not sure what is it.

There is also a maybe relevant dmesg string available:

[Firmware bug]: ACPI: BIOS _OSI(Linux) query ignored

[curaga]

Extra modules on disk may not be relevant. Compare lsmod on both, backlight-related modules.

Screen blanking when lid closed is done by hw, the screen saver is unrelated, and without sw control the backlight defaults to BIOS settings.

[Scampada]

Erm, well. I found differences between TC's lsmod output and that one of openSUSE.

TC lsmod has:
acer_wmi, video, backlight

openSUSE has:
acer_wmi, video, NO backlight and some more additional modules that I am not sure are relevant. e.g. i915, i2c* and something.
(And backlight sw is present.)

One more difference is that TC is using kernel version 3.16.6 and openSUSE has 3.16.6-2. archlinux that I also have in possession and where backlight sw is working, uses even more up-dated 3.18.*

Maybe it depends on kernel version?.. maybe 3.16.6 can't recognize my hw and 3.16.6-2 can?

[curaga]

Then it's likely your backlight is managed by the Intel graphics card. See if the /sys dir is populated when you load the graphics- extension (in CLI, not in X!). If so, you need to use Xorg or Xfbdev, Xvesa cannot be used with KMS.

[Scampada]

Then it's likely your backlight is managed by the Intel graphics card. See if the /sys dir is populated when you load the graphics- extension (in CLI, not in X!). If so, you need to use Xorg or Xfbdev, Xvesa cannot be used with KMS.

Usually, I have no X loaded (except when I'm running angband or dosbox).
Is it right that to use my backlight software properly I have to run Xorg?..

What should I do - when I load the graphics, wait, do I load it?.. Hmm. I shall check and see

[gerald_clark]

Don't your keyboard function keys work to change the brightness?
If not try loading and starting acpid.

[Scampada]

Don't your keyboard function keys work to change the brightness?
If not try loading and starting acpid.

For now, definitely not. Under openSUSE they do, in TC don't.
(But how would they if there weren't bl class?)
I will, thank you.

[Scampada]

The problem isn't that i can't change backlight brightness with Fn keys, the problem is my system believes that I have no backlight at all.

I thought of, maybe openSUSE rewrites BIOS defaults, because after I start openSUSE and lower my brightness and then restart, the screen is dim in GRUB and in TC. And if I start openSUSE and set brightness higher the screen would be brighter under TC after reboot (and even after shutdown!).
So I thought, maybe, can I update those BIOS defaults from TC without configuring the backlight interface itself?.. That would be quite nice then, if these settings would store themselves permanently between sessions.

[Scampada]

Funny that I can not remove the backlight module because it's "IN USE" or something, and still it doesn't create any content in /sys/class/backlight. Sure it's in use because my display is working... But it's used some wrong way.

[curaga]

Did you try graphics-? Xorg is not required, just mentioned that Xvesa is not compatible.