| 1 | =================
|
| 2 | Keyboard notifier
|
| 3 | =================
|
| 4 |
|
| 5 | One can use register_keyboard_notifier to get called back on keyboard
|
| 6 | events (see kbd_keycode() function for details). The passed structure is
|
| 7 | keyboard_notifier_param (see <linux/keyboard.h>):
|
| 8 |
|
| 9 | - 'vc' always provide the VC for which the keyboard event applies;
|
| 10 | - 'down' is 1 for a key press event, 0 for a key release;
|
| 11 | - 'shift' is the current modifier state, mask bit indexes are KG_*;
|
| 12 | - 'ledstate' is the current LED state;
|
| 13 | - 'value' depends on the type of event.
|
| 14 |
|
| 15 | - KBD_KEYCODE events are always sent before other events, value is the keycode.
|
| 16 | - KBD_UNBOUND_KEYCODE events are sent if the keycode is not bound to a keysym.
|
| 17 | value is the keycode.
|
| 18 | - KBD_UNICODE events are sent if the keycode -> keysym translation produced a
|
| 19 | unicode character. value is the unicode value.
|
| 20 | - KBD_KEYSYM events are sent if the keycode -> keysym translation produced a
|
| 21 | non-unicode character. value is the keysym.
|
| 22 | - KBD_POST_KEYSYM events are sent after the treatment of non-unicode keysyms.
|
| 23 | That permits one to inspect the resulting LEDs for instance.
|
| 24 |
|
| 25 | For each kind of event but the last, the callback may return NOTIFY_STOP in
|
| 26 | order to "eat" the event: the notify loop is stopped and the keyboard event is
|
| 27 | dropped.
|
| 28 |
|
| 29 | In a rough C snippet, we have::
|
| 30 |
|
| 31 | kbd_keycode(keycode) {
|
| 32 | ...
|
| 33 | params.value = keycode;
|
| 34 | if ((notifier_call_chain(KBD_KEYCODE,¶ms) == NOTIFY_STOP)
|
| 35 | || !bound) {
|
| 36 | notifier_call_chain(KBD_UNBOUND_KEYCODE,¶ms);
|
| 37 | return;
|
| 38 | }
|
| 39 |
|
| 40 | if (unicode) {
|
| 41 | param.value = unicode;
|
| 42 | if (notifier_call_chain(KBD_UNICODE,¶ms) == NOTIFY_STOP)
|
| 43 | return;
|
| 44 | emit unicode;
|
| 45 | return;
|
| 46 | }
|
| 47 |
|
| 48 | params.value = keysym;
|
| 49 | if (notifier_call_chain(KBD_KEYSYM,¶ms) == NOTIFY_STOP)
|
| 50 | return;
|
| 51 | apply keysym;
|
| 52 | notifier_call_chain(KBD_POST_KEYSYM,¶ms);
|
| 53 | }
|
| 54 |
|
| 55 | .. note:: This notifier is usually called from interrupt context.
|