Add a property to toggle function key mode

On some keyboards, the multimedia function keys are overlaid with the F
keys. This property enables clients to switch the primary mode of these F
keys between function keys and multimedia keys.
Some keyboards provide an Fn key to toggle between the modes. This is
hardware-specific and may or may not work on any given keyboard device.

The current imlementation is only hooked up to apple keyboards.
The kernel provides a tweak to enable/disable.

/sys/module/hid_apple/parameters/fnmode
    0 .. keyboard sends Fx keys, Fn disabled
    1 .. keyboard sends multimedia keys, Fn toggles to function keys
    2 .. keyboard sends function keys, Fn toggles to multimedia keys

If fnmode is on 0, we force it to 2.

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
Reviewed-by: Michel Dänzer <michel@daenzer.net>

1 files changed, 12 insertions, 0 deletions

diff --git a/include/evdev-properties.h b/include/evdev-properties.h
index 16f2af7..745a1ba 100644
--- a/include/evdev-properties.h
+++ b/include/evdev-properties.h
@@ -75,4 +75,16 @@
 /* CARD32 */
 #define EVDEV_PROP_THIRDBUTTON_THRESHOLD "Evdev Third Button Emulation Threshold"
 
+/* CARD8, 1 value,
+   This property is initialized on devices that have multimedia keys on the
+   function keys. The value of the property selects the default behaviour
+   for the function keys. The behaviour of the fn key (if any exists) is
+   hardware specific. On some hardware, fn may toggle the other set of
+   functions available on the keys.
+
+   0 send functions keys by default, fn may toggle to multimedia keys
+   1 send multimedia keys by default, fn may toggle to function keys
+*/
+#define EVDEV_PROP_FUNCTION_KEYS "Evdev Function Keys"
+
 #endif