randy.dunlap at oracle
Feb 8, 2008, 8:12 PM
Post #2 of 5
(432 views)
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Re: [PATCH] keyboard notifier documentation
[In reply to]
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On Sat, 9 Feb 2008 01:33:22 +0000 Samuel Thibault wrote:
> Document the keyboard notifier.
>
> Signed-off-by: Samuel Thibault <samuel.thibault [at] ens-lyon>
>
> --- /dev/null 2008-02-09 01:22:34.790011677 +0000
> +++ linux/Documentation/input/notifier.txt 2008-02-09 01:28:12.000000000 +0000
> @@ -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_* ;
No space before the ';' (3 times).
> +- '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 to inspect the resulting LEDs for instance.
That permits (some object word here, like: you, one, code, etc.) to
inspect ...
> +
> +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.
> +
> +I a rough C snippet, we have:
In a rough (?)
> +
> +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.
> --
---
~Randy
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