Input: adbhid - produce all CapsLock key events

The ADB keyboard, which is used for Apple PowerBooks, has strange behavior
with regard to the capslock key.  It keeps track of capslock state
internally, and it sends a keycode when capslock is engaged and a keycode
when capslock is disengaged.

When the current adbhid driver sees that the capslock key is pressed or
released, it creates both a keypress event and a keyrelease event
simultaneously.  This results in normal capslock behavior.

While this works, it makes it impossible to remap the capslock key to be a
control key.  However, by translating the 0xff keycode into capslock
keycodes, we can restore the missing capslock events and make it possible
to remap the capslock key.

With this patch, the adbhid driver will translate these 0xff keycodes into
capslock keypresses and keyreleases if
/sys/module/adbhid/parameters/restore_capslock_events is set to 1.
Otherwise it will retain the current behavior.  This option is off by
default because occasionally the 0xff keycode is not a capslock event, and
a mistake may require the user to tap the capslock key.

[akpm@linux-foundation.org: cleanups]
Signed-off-by: Andrew McNabb <amcnabb@mcnabbs.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>

drivers/macintosh/adbhid.c

@@ -52,6 +52,11 @@
 
 MODULE_AUTHOR("Franz Sirl <Franz.Sirl-kernel@lauterbach.com>");
 
+static int restore_capslock_events;
+module_param(restore_capslock_events, int, 0644);
+MODULE_PARM_DESC(restore_capslock_events,
+	"Produce keypress events for capslock on both keyup and keydown.");
+
 #define KEYB_KEYREG	0	/* register # for key up/down data */
 #define KEYB_LEDREG	2	/* register # for leds on ADB keyboard */
 #define MOUSE_DATAREG	0	/* reg# for movement/button codes from mouse */
@@ -217,6 +222,8 @@ struct adbhid {
 #define FLAG_FN_KEY_PRESSED	0x00000001
 #define FLAG_POWER_FROM_FN	0x00000002
 #define FLAG_EMU_FWDEL_DOWN	0x00000004
+#define FLAG_CAPSLOCK_TRANSLATE	0x00000008
+#define FLAG_CAPSLOCK_DOWN	0x00000010
 
 static struct adbhid *adbhid[16];
 
@@ -272,19 +279,50 @@ adbhid_keyboard_input(unsigned char *data, int nb, int apoll)
 }
 
 static void
-adbhid_input_keycode(int id, int keycode, int repeat)
+adbhid_input_keycode(int id, int scancode, int repeat)
 {
 	struct adbhid *ahid = adbhid[id];
-	int up_flag;
-
-	up_flag = (keycode & 0x80);
-	keycode &= 0x7f;
+	int keycode, up_flag;
+
+	keycode = scancode & 0x7f;
+	up_flag = scancode & 0x80;
+
+	if (restore_capslock_events) {
+		if (keycode == ADB_KEY_CAPSLOCK && !up_flag) {
+			/* Key pressed, turning on the CapsLock LED.
+			 * The next 0xff will be interpreted as a release. */
+			ahid->flags |= FLAG_CAPSLOCK_TRANSLATE
+					| FLAG_CAPSLOCK_DOWN;
+		} else if (scancode == 0xff) {
+			/* Scancode 0xff usually signifies that the capslock
+			 * key was either pressed or released. */
+			if (ahid->flags & FLAG_CAPSLOCK_TRANSLATE) {
+				keycode = ADB_KEY_CAPSLOCK;
+				if (ahid->flags & FLAG_CAPSLOCK_DOWN) {
+					/* Key released */
+					up_flag = 1;
+					ahid->flags &= ~FLAG_CAPSLOCK_DOWN;
+				} else {
+					/* Key pressed */
+					up_flag = 0;
+					ahid->flags &= ~FLAG_CAPSLOCK_TRANSLATE;
+				}
+			} else {
+				printk(KERN_INFO "Spurious caps lock event "
+						"(scancode 0xff).");
+			}
+		}
+	}
 
 	switch (keycode) {
-	case ADB_KEY_CAPSLOCK: /* Generate down/up events for CapsLock everytime. */
-		input_report_key(ahid->input, KEY_CAPSLOCK, 1);
-		input_report_key(ahid->input, KEY_CAPSLOCK, 0);
-		input_sync(ahid->input);
+	case ADB_KEY_CAPSLOCK:
+		if (!restore_capslock_events) {
+			/* Generate down/up events for CapsLock everytime. */
+			input_report_key(ahid->input, KEY_CAPSLOCK, 1);
+			input_sync(ahid->input);
+			input_report_key(ahid->input, KEY_CAPSLOCK, 0);
+			input_sync(ahid->input);
+		}
 		return;
 #ifdef CONFIG_PPC_PMAC
 	case ADB_KEY_POWER_OLD: /* Power key on PBook 3400 needs remapping */