From mboxrd@z Thu Jan 1 00:00:00 1970 From: Samuel Thibault Subject: [PATCH] keyboard notifier documentation Date: Sat, 9 Feb 2008 01:33:22 +0000 Message-ID: <20080209013322.GC4463@implementation> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org To: torvalds@osdl.org, linux-input@vger.kernel.org, dtor@mail.ru Cc: linux-kernel@vger.kernel.org List-Id: linux-input@vger.kernel.org Document the keyboard notifier. Signed-off-by: Samuel Thibault --- /dev/null 2008-02-09 01:22:34.790011677 +0000 +++ linux/Documentation/input/notifier.txt 2008-02-09 01:28:12.00000000= 0 +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=A0; +- 'down' is 1 for a key press event, 0 for a key release=A0; +- 'shift' is the current modifier state, mask bit indexes are KG_*=A0; +- '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 pro= duced a + unicode character. value is the unicode value. +- KBD_KEYSYM events are sent if the keycode -> keysym translation prod= uced a + non-unicode character. value is the keysym. +- KBD_POST_KEYSYM events are sent after the treatment of non-unicode k= eysyms. + That permits to inspect the resulting LEDs for instance. + +For each kind of event but the last, the callback may return NOTIFY_ST= OP in +order to "eat" the event: the notify loop is stopped and the keyboard = event is +dropped. + +I a rough C snippet, we have: + +kbd_keycode(keycode) { + ... + params.value =3D keycode; + if (notifier_call_chain(KBD_KEYCODE,¶ms) =3D=3D NOTIFY_STOP) + || !bound) { + notifier_call_chain(KBD_UNBOUND_KEYCODE,¶ms); + return; + } + + if (unicode) { + param.value =3D unicode; + if (notifier_call_chain(KBD_UNICODE,¶ms) =3D=3D NOTIFY_STOP) + return; + emit unicode; + return; + } + + params.value =3D keysym; + if (notifier_call_chain(KBD_KEYSYM,¶ms) =3D=3D NOTIFY_STOP) + return; + apply keysym; + notifier_call_chain(KBD_POST_KEYSYM,¶ms); +} + +NOTE: This notifier is usually called from interrupt context.