Paul Abrahams wrote:
One of my keyboards has a key labelled "Fn", on the right side below the Enter key. (It's a Dynapoint made in China, but that information probably isn't helpful.) Of all the keys on the keyboard, it's the only one that is not detected by xev, and it doesn't produce a dmesg entry either. I also tried using it as a shift key with other keys, but it doesn't seem to affect their keycodes.
I washed my keyboard several days ago and it wasn't working for a while, but it seems to have dried out, and this is the only key that doesn't work now. It seems unlikely that the bath affected just that one mysterious key.
Does anyone know what that Fn key might be for?
Fn is typically found on laptop and other undersized keyboards. It's used to create the missing keys. For instance, 7,8,9,U,I,O,etc form the number pad when combined with Fn on my keyboard. Fn+PgUp and Fn+PgDwn for volume. As I understand it, the change is done in hardware, not software, that's why you don't see it in XEV. However, I don't believe there is an established standard for these things.