Commit e32f7ee876ebbdec73e4c19dce559a20c2ab840e
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Dmitry Torokhov
Dmitry Torokhov
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Input: add keyboard notifier documentation
Document the keyboard notifier. Signed-off-by: Samuel Thibault <samuel.thibault@ens-lyon.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Jiri Kosina <jkosina@suse.cz> SIgned-off-by: Dmitry Torokhov <dtor@mail.ru>
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Documentation/input/notifier.txt
| 1 | +Keyboard notifier | |
| 2 | + | |
| 3 | +One can use register_keyboard_notifier to get called back on keyboard | |
| 4 | +events (see kbd_keycode() function for details). The passed structure is | |
| 5 | +keyboard_notifier_param: | |
| 6 | + | |
| 7 | +- 'vc' always provide the VC for which the keyboard event applies; | |
| 8 | +- 'down' is 1 for a key press event, 0 for a key release; | |
| 9 | +- 'shift' is the current modifier state, mask bit indexes are KG_*; | |
| 10 | +- 'value' depends on the type of event. | |
| 11 | + | |
| 12 | +- KBD_KEYCODE events are always sent before other events, value is the keycode. | |
| 13 | +- KBD_UNBOUND_KEYCODE events are sent if the keycode is not bound to a keysym. | |
| 14 | + value is the keycode. | |
| 15 | +- KBD_UNICODE events are sent if the keycode -> keysym translation produced a | |
| 16 | + unicode character. value is the unicode value. | |
| 17 | +- KBD_KEYSYM events are sent if the keycode -> keysym translation produced a | |
| 18 | + non-unicode character. value is the keysym. | |
| 19 | +- KBD_POST_KEYSYM events are sent after the treatment of non-unicode keysyms. | |
| 20 | + That permits one to inspect the resulting LEDs for instance. | |
| 21 | + | |
| 22 | +For each kind of event but the last, the callback may return NOTIFY_STOP in | |
| 23 | +order to "eat" the event: the notify loop is stopped and the keyboard event is | |
| 24 | +dropped. | |
| 25 | + | |
| 26 | +In a rough C snippet, we have: | |
| 27 | + | |
| 28 | +kbd_keycode(keycode) { | |
| 29 | + ... | |
| 30 | + params.value = keycode; | |
| 31 | + if (notifier_call_chain(KBD_KEYCODE,¶ms) == NOTIFY_STOP) | |
| 32 | + || !bound) { | |
| 33 | + notifier_call_chain(KBD_UNBOUND_KEYCODE,¶ms); | |
| 34 | + return; | |
| 35 | + } | |
| 36 | + | |
| 37 | + if (unicode) { | |
| 38 | + param.value = unicode; | |
| 39 | + if (notifier_call_chain(KBD_UNICODE,¶ms) == NOTIFY_STOP) | |
| 40 | + return; | |
| 41 | + emit unicode; | |
| 42 | + return; | |
| 43 | + } | |
| 44 | + | |
| 45 | + params.value = keysym; | |
| 46 | + if (notifier_call_chain(KBD_KEYSYM,¶ms) == NOTIFY_STOP) | |
| 47 | + return; | |
| 48 | + apply keysym; | |
| 49 | + notifier_call_chain(KBD_POST_KEYSYM,¶ms); | |
| 50 | +} | |
| 51 | + | |
| 52 | +NOTE: This notifier is usually called from interrupt context. |