Console keyboard events and accessibility

Some blind people use a kernel engine called Speakup which uses hardware
synthesis to speak what gets displayed on the screen.  They use the
PC keyboard to control this engine (start/stop, accelerate, ...) and
also need to get keyboard feedback (to make sure to know what they are
typing, the caps lock status, etc.)

Up to now, the way it was done was very ugly.  Below is a patch to add a
notifier list for permitting a far better implementation, see ChangeLog
above for details.

You may wonder why this can't be done at the input layer.  The problem
is that what people want to monitor is the console keyboard, i.e. all
input keyboards that got attached to the console, and with the currently
active keymap (i.e. keysyms, not only keycodes).

This adds a keyboard notifier that such modules can use to get the keyboard
events and possibly eat them, at several stages:

- keycodes: even before translation into keysym.
- unbound keycodes: when no keysym is bound.
- unicode: when the keycode would get translated into a unicode character.
- keysym: when the keycode would get translated into a keysym.
- post_keysym: after the keysym got interpreted, so as to see the result
  (caps lock, etc.)

This also provides access to k_handler so as to permit simulation of
keypresses.

[akpm@linux-foundation.org: various fixes]
Signed-off-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
Cc: Jiri Kosina <jkosina@suse.cz>
Cc: Dmitry Torokhov <dtor@mail.ru>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 9 insertions, 0 deletions

diff --git a/include/linux/notifier.h b/include/linux/notifier.h
index fad7ff17e468..bd3788084fa9 100644
--- a/include/linux/notifier.h
+++ b/include/linux/notifier.h
@@ -231,5 +231,14 @@ static inline int notifier_to_errno(int ret)
 #define PM_SUSPEND_PREPARE      0x0003 /* Going to suspend the system */
 #define PM_POST_SUSPEND         0x0004 /* Suspend finished */
 
+/* Console keyboard events.
+ * Note: KBD_KEYCODE is always sent before KBD_UNBOUND_KEYCODE, KBD_UNICODE and
+ * KBD_KEYSYM. */
+#define KBD_KEYCODE             0x0001 /* Keyboard keycode, called before any other */
+#define KBD_UNBOUND_KEYCODE     0x0002 /* Keyboard keycode which is not bound to any other */
+#define KBD_UNICODE             0x0003 /* Keyboard unicode */
+#define KBD_KEYSYM              0x0004 /* Keyboard keysym */
+#define KBD_POST_KEYSYM         0x0005 /* Called after keyboard keysym interpretation */
+
 #endif /* __KERNEL__ */
 #endif /* _LINUX_NOTIFIER_H */