blob: 824379399e611e46cd5d5ca93922efa974c0094b [file] [log] [blame]
Keyboard notifier
One can use register_keyboard_notifier to get called back on keyboard
events (see kbd_keycode() function for details). The passed structure is
keyboard_notifier_param (see <linux/keyboard.h>):
- 'vc' always provide the VC for which the keyboard event applies;
- 'down' is 1 for a key press event, 0 for a key release;
- 'shift' is the current modifier state, mask bit indexes are KG_*;
- 'ledstate' is the current LED state;
- 'value' depends on the type of event.
- KBD_KEYCODE events are always sent before other events, value is the keycode.
- KBD_UNBOUND_KEYCODE events are sent if the keycode is not bound to a keysym.
value is the keycode.
- KBD_UNICODE events are sent if the keycode -> keysym translation produced a
unicode character. value is the unicode value.
- KBD_KEYSYM events are sent if the keycode -> keysym translation produced a
non-unicode character. value is the keysym.
- KBD_POST_KEYSYM events are sent after the treatment of non-unicode keysyms.
That permits one to inspect the resulting LEDs for instance.
For each kind of event but the last, the callback may return NOTIFY_STOP in
order to "eat" the event: the notify loop is stopped and the keyboard event is
In a rough C snippet, we have::
kbd_keycode(keycode) {
params.value = keycode;
if (notifier_call_chain(KBD_KEYCODE,&params) == NOTIFY_STOP)
|| !bound) {
if (unicode) {
param.value = unicode;
if (notifier_call_chain(KBD_UNICODE,&params) == NOTIFY_STOP)
emit unicode;
params.value = keysym;
if (notifier_call_chain(KBD_KEYSYM,&params) == NOTIFY_STOP)
apply keysym;
.. note:: This notifier is usually called from interrupt context.