ilejn
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Latitude e7440 A14 bios update breaks brightness key control in Ubuntu

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Hello.

e7440 A14, Ubuntu 14.10, kernel 3.18.

It is possible to control brightness writing to /sys/class/backlight/intel_backlight/brightness or via system/brihtness and look, but buttons do not work.

According to xev Fn/Up or Down simply do not generate any event.

To restore functioning I need to run suspend to RAM (not hibernate). I failed to detect anything specific in pm-utils scripts and it seems that suspend helps by itself.

Unfortunately I do not have Windows to check, but I definitely did not have this issue against neither A08 nor A12.

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ilejn
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RE: Latitude e7440 A14 bios update breaks brightness key control in Ubuntu

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acpi_listen says only

 PNP0C14:00 000000d0 00000000

both for brightness Up and Down, while after resuming from suspend it is

video/brightnessdown BRTDN 00000087 00000000
 PNP0C14:00 000000d0 00000000
video/brightnessup BRTUP 00000086 00000000
 PNP0C14:00 000000d0 00000000

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ilejn
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RE: Latitude e7440 A14 bios update breaks brightness key control in Ubuntu

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Adding boot parameters acpi_osi=Linux acpi_backlight=vendor

resolves this issue for me.

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