Messages in this thread | | | Date | Thu, 19 May 2011 20:53:53 +0200 | Subject | Re: samsung-laptop backlight control not working | From | David Herrmann <> |
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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
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