Need to ask user to "Touch yubikey to continue"

[Fry-kun]

If programmed with "require user input", yubikey will wait for the user to touch it before generating a response. ykfde should detect this condition and display some message to the user.

If it's not trivial, this can be faked by always asking "Touch yubikey to continue" -- or by looking at how long it takes for Yubikey to respond (if >a few msec, user input is probably required)

[Fry-kun]

This is especially problematic during boot, since it's not clear if I need to touch the yubikey before entering the passphrase (seems like that's the case?)

[eworm-de]

The actual work is done by a udev helper that does not have access to the terminal. So we can not display any messages.

[agowa]

What about just printing If required press the button on your yubikey to continue. Before invoking the udev helper? The message should only be barely visible if it is not required as the boot process silently continues. And if it is required it will stay on screen until the user has pressed the button.