samsung-laptop backlight control not working

samsung-laptop backlight control not working

[David Herrmann]

Hi

I tried the new samsung-laptop driver with samsung backlight support.
It is detected as:
[109282.931433] samsung_laptop: found laptop model 'N150P/N210P/N220P'

However, backlight support is kind of weird:
"echo 1 >/sys/class/backlight/samsung/brightness"
does not set brightness to 1 but instead reduces brightness for 1.
That is, if my current brightness setting is 8, I need to call "echo 1
>..." 7 times to get brightness value 1.

"cat /sys/class/backlight...."
returns 1 after the first try, though.

"echo 3 >..."
reduces brightness also for 1 but stops at brightness level 3 if I
repeat the command.

dmesg shows the following for every "echo" I call:
[110690.073783] ACPI: Failed to switch the brightness

Furthermore "echo 0 >..." doesn't disable backlight but instead
behaves like a brightness setting below 1.


However, I know the following works on my machine:
setpci -s 00:02.0 F4.B=255
It accepts a setting between 0-255 and 255 is full brightness and 0 is
backlight off.


Regards
David

Re: samsung-laptop backlight control not working

[Greg KH]

On Thu, May 19, 2011 at 08:18:16PM +0200, David Herrmann wrote:
> Hi
> 
> I tried the new samsung-laptop driver with samsung backlight support.

What kernel are you trying?  We have some recent patches to the driver
to try to resolve some of these issues on your laptop.

> It is detected as:
> [109282.931433] samsung_laptop: found laptop model 'N150P/N210P/N220P'
> 
> However, backlight support is kind of weird:
> "echo 1 >/sys/class/backlight/samsung/brightness"
> does not set brightness to 1 but instead reduces brightness for 1.
> That is, if my current brightness setting is 8, I need to call "echo 1
> >..." 7 times to get brightness value 1.
> 
> "cat /sys/class/backlight...."
> returns 1 after the first try, though.
> 
> "echo 3 >..."
> reduces brightness also for 1 but stops at brightness level 3 if I
> repeat the command.
> 
> dmesg shows the following for every "echo" I call:
> [110690.073783] ACPI: Failed to switch the brightness
> 
> Furthermore "echo 0 >..." doesn't disable backlight but instead
> behaves like a brightness setting below 1.

Yeah, don't echo 0 there, that doesn't work to well.  I have some
patches here that you can try if you want, just let me know.

> However, I know the following works on my machine:
> setpci -s 00:02.0 F4.B=255
> It accepts a setting between 0-255 and 255 is full brightness and 0 is
> backlight off.

Don't do that, the video driver will not like you as you are changing
things without telling the bios that something is really happening.

Of course you can continue to do this, it's just strongly not
recommended.

thanks,

greg k-h

Re: samsung-laptop backlight control not working

[David Herrmann]

On Thu, May 19, 2011 at 8:27 PM, Greg KH <gregkh@suse.de> wrote:
> On Thu, May 19, 2011 at 08:18:16PM +0200, David Herrmann wrote:
>> Hi
>>
>> I tried the new samsung-laptop driver with samsung backlight support.
>
> What kernel are you trying?  We have some recent patches to the driver
> to try to resolve some of these issues on your laptop.

I use linus' tree. 2.6.39

>> It is detected as:
>> [109282.931433] samsung_laptop: found laptop model 'N150P/N210P/N220P'
>>
>> However, backlight support is kind of weird:
>> "echo 1 >/sys/class/backlight/samsung/brightness"
>> does not set brightness to 1 but instead reduces brightness for 1.
>> That is, if my current brightness setting is 8, I need to call "echo 1
>> >..." 7 times to get brightness value 1.
>>
>> "cat /sys/class/backlight...."
>> returns 1 after the first try, though.
>>
>> "echo 3 >..."
>> reduces brightness also for 1 but stops at brightness level 3 if I
>> repeat the command.
>>
>> dmesg shows the following for every "echo" I call:
>> [110690.073783] ACPI: Failed to switch the brightness
>>
>> Furthermore "echo 0 >..." doesn't disable backlight but instead
>> behaves like a brightness setting below 1.
>
> Yeah, don't echo 0 there, that doesn't work to well.  I have some
> patches here that you can try if you want, just let me know.

That would be great! I have really no idea about acpi so I can't fix
it myself. If you could give me some git tree where I can find them, I
could test them.

>> However, I know the following works on my machine:
>> setpci -s 00:02.0 F4.B=255
>> It accepts a setting between 0-255 and 255 is full brightness and 0 is
>> backlight off.
>
> Don't do that, the video driver will not like you as you are changing
> things without telling the bios that something is really happening.
>
> Of course you can continue to do this, it's just strongly not
> recommended.

Ouh, I didn't know that. It was recommended in some distro wiki so I
tried it and it worked. Anyway, I thought it might give you some
information about the N210 model.

> thanks,
>
> greg k-h

Thanks
David

Re: samsung-laptop backlight control not working

[David Herrmann]

Hi Greg

On Thu, May 19, 2011 at 8:53 PM, David Herrmann
<dh.herrmann@googlemail.com> wrote:
> On Thu, May 19, 2011 at 8:27 PM, Greg KH <gregkh@suse.de> wrote:
>> On Thu, May 19, 2011 at 08:18:16PM +0200, David Herrmann wrote:
>>> Hi
>>>
>>> I tried the new samsung-laptop driver with samsung backlight support.
>>
>> What kernel are you trying?  We have some recent patches to the driver
>> to try to resolve some of these issues on your laptop.
>
> I use linus' tree. 2.6.39
>
>>> It is detected as:
>>> [109282.931433] samsung_laptop: found laptop model 'N150P/N210P/N220P'
>>>
>>> However, backlight support is kind of weird:
>>> "echo 1 >/sys/class/backlight/samsung/brightness"
>>> does not set brightness to 1 but instead reduces brightness for 1.
>>> That is, if my current brightness setting is 8, I need to call "echo 1
>>> >..." 7 times to get brightness value 1.
>>>
>>> "cat /sys/class/backlight...."
>>> returns 1 after the first try, though.
>>>
>>> "echo 3 >..."
>>> reduces brightness also for 1 but stops at brightness level 3 if I
>>> repeat the command.
>>>
>>> dmesg shows the following for every "echo" I call:
>>> [110690.073783] ACPI: Failed to switch the brightness
>>>
>>> Furthermore "echo 0 >..." doesn't disable backlight but instead
>>> behaves like a brightness setting below 1.
>>
>> Yeah, don't echo 0 there, that doesn't work to well.  I have some
>> patches here that you can try if you want, just let me know.
>
> That would be great! I have really no idea about acpi so I can't fix
> it myself. If you could give me some git tree where I can find them, I
> could test them.
>
>>> However, I know the following works on my machine:
>>> setpci -s 00:02.0 F4.B=255
>>> It accepts a setting between 0-255 and 255 is full brightness and 0 is
>>> backlight off.
>>
>> Don't do that, the video driver will not like you as you are changing
>> things without telling the bios that something is really happening.
>>
>> Of course you can continue to do this, it's just strongly not
>> recommended.
>
> Ouh, I didn't know that. It was recommended in some distro wiki so I
> tried it and it worked. Anyway, I thought it might give you some
> information about the N210 model.
>
>> thanks,
>>
>> greg k-h
>
> Thanks
> David

Maybe you missed that mail, any update on this? Where could I get
those patches? ;)

Thanks
David

Re: samsung-laptop backlight control not working

[Greg KH]

On Wed, Jun 01, 2011 at 04:50:17PM +0200, David Herrmann wrote:
> Hi Greg
> 
> On Thu, May 19, 2011 at 8:53 PM, David Herrmann
> <dh.herrmann@googlemail.com> wrote:
> > On Thu, May 19, 2011 at 8:27 PM, Greg KH <gregkh@suse.de> wrote:
> >> On Thu, May 19, 2011 at 08:18:16PM +0200, David Herrmann wrote:
> >>> Hi
> >>>
> >>> I tried the new samsung-laptop driver with samsung backlight support.
> >>
> >> What kernel are you trying?  We have some recent patches to the driver
> >> to try to resolve some of these issues on your laptop.
> >
> > I use linus' tree. 2.6.39
> >
> >>> It is detected as:
> >>> [109282.931433] samsung_laptop: found laptop model 'N150P/N210P/N220P'
> >>>
> >>> However, backlight support is kind of weird:
> >>> "echo 1 >/sys/class/backlight/samsung/brightness"
> >>> does not set brightness to 1 but instead reduces brightness for 1.
> >>> That is, if my current brightness setting is 8, I need to call "echo 1
> >>> >..." 7 times to get brightness value 1.
> >>>
> >>> "cat /sys/class/backlight...."
> >>> returns 1 after the first try, though.
> >>>
> >>> "echo 3 >..."
> >>> reduces brightness also for 1 but stops at brightness level 3 if I
> >>> repeat the command.
> >>>
> >>> dmesg shows the following for every "echo" I call:
> >>> [110690.073783] ACPI: Failed to switch the brightness
> >>>
> >>> Furthermore "echo 0 >..." doesn't disable backlight but instead
> >>> behaves like a brightness setting below 1.
> >>
> >> Yeah, don't echo 0 there, that doesn't work to well.  I have some
> >> patches here that you can try if you want, just let me know.
> >
> > That would be great! I have really no idea about acpi so I can't fix
> > it myself. If you could give me some git tree where I can find them, I
> > could test them.
> >
> >>> However, I know the following works on my machine:
> >>> setpci -s 00:02.0 F4.B=255
> >>> It accepts a setting between 0-255 and 255 is full brightness and 0 is
> >>> backlight off.
> >>
> >> Don't do that, the video driver will not like you as you are changing
> >> things without telling the bios that something is really happening.
> >>
> >> Of course you can continue to do this, it's just strongly not
> >> recommended.
> >
> > Ouh, I didn't know that. It was recommended in some distro wiki so I
> > tried it and it worked. Anyway, I thought it might give you some
> > information about the N210 model.
> >
> >> thanks,
> >>
> >> greg k-h
> >
> > Thanks
> > David
> 
> Maybe you missed that mail, any update on this? Where could I get
> those patches? ;)

Ick, sorry, they can be found at:
	http://git.kernel.org/?p=linux/kernel/git/gregkh/patches.git;a=tree

I need to push them to Michael soon, I've been swamped with other stuff
at the moment, sorry about this.

greg k-h