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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 000000000000..95172ca6f3d2 --- /dev/null +++ b/Documentation/input/notifier.txt | |||
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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. | ||