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Diffstat (limited to 'Documentation/input/notifier.txt')
| -rw-r--r-- | Documentation/input/notifier.txt | 52 |
1 files changed, 52 insertions, 0 deletions
diff --git a/Documentation/input/notifier.txt b/Documentation/input/notifier.txt new file mode 100644 index 000000000..95172ca6f --- /dev/null +++ b/Documentation/input/notifier.txt @@ -0,0 +1,52 @@ +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: + +- '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_*; +- '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 +dropped. + +In a rough C snippet, we have: + +kbd_keycode(keycode) { + ... + params.value = keycode; + if (notifier_call_chain(KBD_KEYCODE,¶ms) == NOTIFY_STOP) + || !bound) { + notifier_call_chain(KBD_UNBOUND_KEYCODE,¶ms); + return; + } + + if (unicode) { + param.value = unicode; + if (notifier_call_chain(KBD_UNICODE,¶ms) == NOTIFY_STOP) + return; + emit unicode; + return; + } + + params.value = keysym; + if (notifier_call_chain(KBD_KEYSYM,¶ms) == NOTIFY_STOP) + return; + apply keysym; + notifier_call_chain(KBD_POST_KEYSYM,¶ms); +} + +NOTE: This notifier is usually called from interrupt context. |