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, 11 insertions, 0 deletions

diff --git a/include/linux/keyboard.h b/include/linux/keyboard.h
index 33b5c2e325b9..65c2d70853e9 100644
--- a/include/linux/keyboard.h
+++ b/include/linux/keyboard.h
@@ -23,10 +23,21 @@
 #define MAX_NR_OF_USER_KEYMAPS 256      /* should be at least 7 */
 
 #ifdef __KERNEL__
+struct notifier_block;
 extern const int NR_TYPES;
 extern const int max_vals[];
 extern unsigned short *key_maps[MAX_NR_KEYMAPS];
 extern unsigned short plain_map[NR_KEYS];
+
+struct keyboard_notifier_param {
+        struct vc_data *vc;     /* VC on which the keyboard press was done */
+        int down;               /* Pressure of the key? */
+        int shift;              /* Current shift mask */
+        unsigned int value;     /* keycode, unicode value or keysym */
+};
+
+extern int register_keyboard_notifier(struct notifier_block *nb);
+extern int unregister_keyboard_notifier(struct notifier_block *nb);
 #endif
 
 #define MAX_NR_FUNC     256     /* max nr of strings assigned to keys */