linux-kernel - Side effect of pressing special keys

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Date:	Sun, 23 Nov 2014 14:41:17 +0100
From:	Pali Rohár <pali.rohar@...il.com>
To:	linux-input@...r.kernel.org, platform-driver-x86@...r.kernel.org
Cc:	Gabriele Mazzotta <gabriele.mzt@...il.com>,
	linux-kernel@...r.kernel.org
Subject: Side effect of pressing special keys

Hello,

pressing some keys on laptops could cause some side effects.

Example scenario 1:

Laptop has Fn key for enabling/disabling WIFI and when that key 
is pressed BIOS is doing two things:

1) Switch hard rfkill state of WIFI
2) Report that Fn key was pressed to kernel
   (either via i8042 bus or via ACPI/WMI)

Example scenario 2:

Another laptop has Fn key too, but BIOS does not change state of 
hard rfkill. So system (kernel or userspace) is responsible for 
interpreting what that Fn key means and call correct action (find 
rfkill device for WIFI and soft block it).

And my questions are:

1) What should userspace do if some input device report that 
KEY_WLAN or KEY_RFKILL was pressed?

2) Should kernel report to userspace that (on specific laptop) 
has pressed key some side effect?

3) How to deal with existing userspace application which 
interpret all pressed keys as described in example scenario 2 
also on laptops from scenario 1? KDE4, NetworkManager, ... are 
know to do that!

Note that this problem is not only about rfkill/wifi keys. Same 
apply for keyboard brightness Fn keys and also for key 
KEY_KBDILLUMTOGGLE (which toggle keyboard illumination level).

-- 
Pali Rohár
pali.rohar@...il.com

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