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Date: Thu, 19 May 2011 20:18:16 +0200 From: David Herrmann <dh.herrmann@...glemail.com> To: linux-kernel@...r.kernel.org Cc: gregkh@...e.de, mjg@...hat.com, David Herrmann <dh.herrmann@...glemail.com> Subject: samsung-laptop backlight control not working 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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