linux-kernel - Re (hello?): [PATCH] Let keyboard notifiers modify key codes

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Message-ID: <20090109212358.GG5073@const.famille.thibault.fr>
Date:	Fri, 9 Jan 2009 22:23:58 +0100
From:	Samuel Thibault <samuel.thibault@...-lyon.org>
To:	linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
	dmitry.torokhov@...il.com, linux-input@...r.kernel.org
Subject: Re (hello?): [PATCH] Let keyboard notifiers modify key codes

Hello,

Came somebody have a look at this?  The need is real, the only question
that comes to my mind is whether notifiers are allowed to modify the
param they are given.  Since they are not marked const, I'd guess it'd
be ok?

Samuel

Samuel Thibault, le Wed 07 Jan 2009 01:58:13 +0100, a écrit :


Make kbd_keycode() read param.value after calling the keyboard notification
chain, to let the callee change the translation on the fly. This for instance
permits to remap the physical positions of the keys independently of the
configured keymap, for e.g. single-handed people.

Signed-off-by: Samuel Thibault <samuel.thibault@...-lyon.org>

--- linux/drivers/char/keyboard.c.orig	2009-01-07 00:48:46.000000000 +0100
+++ linux/drivers/char/keyboard.c	2009-01-07 01:02:05.000000000 +0100
@@ -1248,6 +1248,7 @@ kbd_keycode
 		kbd->slockstate = 0;
 		return;
 	}
+	keycode = param.value;
 
 	if (keycode >= NR_KEYS)
 		if (keycode >= KEY_BRL_DOT1 && keycode <= KEY_BRL_DOT8)
@@ -1263,6 +1264,7 @@ kbd_keycode
 		param.value = keysym;
 		if (atomic_notifier_call_chain(&keyboard_notifier_list, KBD_UNICODE, &param) == NOTIFY_STOP)
 			return;
+		keysym = param.value;
 		if (down && !raw_mode)
 			to_utf8(vc, keysym);
 		return;
@@ -1282,6 +1284,7 @@ kbd_keycode
 
 	if (atomic_notifier_call_chain(&keyboard_notifier_list, KBD_KEYSYM, &param) == NOTIFY_STOP)
 		return;
+	keysym = param.value;
 
 	if (raw_mode && type != KT_SPEC && type != KT_SHIFT)
 		return;
--- linux/Documentation/input/notifier.txt.orig	2008-04-17 12:14:30.000000000 +0200
+++ linux/Documentation/input/notifier.txt	2009-01-07 01:04:16.000000000 +0100
@@ -21,7 +21,8 @@
 
 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.
+dropped.  The callee can also modify param.value so as to change the key
+translation.
 
 In a rough C snippet, we have:
 
@@ -33,18 +34,26 @@
 		notifier_call_chain(KBD_UNBOUND_KEYCODE,&params);
 		return;
 	}
+	keycode = param.value;
+
+	...
 
 	if (unicode) {
 		param.value = unicode;
 		if (notifier_call_chain(KBD_UNICODE,&params) == NOTIFY_STOP)
 			return;
+		keysym = param.value;
 		emit unicode;
 		return;
 	}
 
+	...
+
 	params.value = keysym;
 	if (notifier_call_chain(KBD_KEYSYM,&params) == NOTIFY_STOP)
 		return;
+	keysym = params.value;
+
 	apply keysym;
 	notifier_call_chain(KBD_POST_KEYSYM,&params);
 }
--
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