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Subject[PATCH] vt: Add virtual console keyboard mode OFF
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Add a new mode for the virtual console keyboard OFF to compliment RAW
in which all key events are ignored. New mode prevents vt input
buffers from overflowing when a program opens but doesn't read from a
tty, like Xorg using only evdev for input.

The new mode is available by the ioctl KDSKBMODE with argument K_OFF
from linux/kd.h. Does not effect sysrq behaviour.

Cc: Greg Kroah-Hartman <gregkh@suse.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Alan Cox <alan@redhat.com>
Signed-off-by: Arthur Taylor <art@ified.ca>
---
drivers/tty/vt/keyboard.c | 5 +++--
drivers/tty/vt/vt_ioctl.c | 3 +++
include/linux/kbd_kern.h | 3 ++-
include/linux/kd.h | 1 +
4 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/drivers/tty/vt/keyboard.c b/drivers/tty/vt/keyboard.c
index e95d787..6dd3c68 100644
--- a/drivers/tty/vt/keyboard.c
+++ b/drivers/tty/vt/keyboard.c
@@ -654,7 +654,8 @@ static void k_spec(struct vc_data *vc, unsigned
char value, char up_flag)
if (value >= ARRAY_SIZE(fn_handler))
return;
if ((kbd->kbdmode == VC_RAW ||
- kbd->kbdmode == VC_MEDIUMRAW) &&
+ kbd->kbdmode == VC_MEDIUMRAW ||
+ kbd->kbdmode == VC_OFF) &&
value != KVAL(K_SAK))
return; /* SAK is allowed even in raw mode */
fn_handler[value](vc);
@@ -1295,7 +1296,7 @@ static void kbd_keycode(unsigned int keycode,
int down, int hw_raw)
if (rc == NOTIFY_STOP)
return;

- if (raw_mode && type != KT_SPEC && type != KT_SHIFT)
+ if ((raw_mode || kbd->kbdmode == VC_OFF) && type != KT_SPEC && type
!= KT_SHIFT)
return;

(*k_handler[type])(vc, keysym & 0xff, !down);
diff --git a/drivers/tty/vt/vt_ioctl.c b/drivers/tty/vt/vt_ioctl.c
index 1235ebd..6bcf05b 100644
--- a/drivers/tty/vt/vt_ioctl.c
+++ b/drivers/tty/vt/vt_ioctl.c
@@ -688,6 +688,9 @@ int vt_ioctl(struct tty_struct *tty, struct file * file,
kbd->kbdmode = VC_UNICODE;
compute_shiftstate();
break;
+ case K_OFF:
+ kbd->kbdmode = VC_OFF;
+ break;
default:
ret = -EINVAL;
goto out;
diff --git a/include/linux/kbd_kern.h b/include/linux/kbd_kern.h
index 506ad20..4b0761c 100644
--- a/include/linux/kbd_kern.h
+++ b/include/linux/kbd_kern.h
@@ -50,11 +50,12 @@ struct kbd_struct {
#define VC_CAPSLOCK 2 /* capslock mode */
#define VC_KANALOCK 3 /* kanalock mode */

- unsigned char kbdmode:2; /* one 2-bit value */
+ unsigned char kbdmode:3; /* one 3-bit value */
#define VC_XLATE 0 /* translate keycodes using keymap */
#define VC_MEDIUMRAW 1 /* medium raw (keycode) mode */
#define VC_RAW 2 /* raw (scancode) mode */
#define VC_UNICODE 3 /* Unicode mode */
+#define VC_OFF 4 /* disabled mode */

unsigned char modeflags:5;
#define VC_APPLIC 0 /* application key mode */
diff --git a/include/linux/kd.h b/include/linux/kd.h
index 15f2853..c36d847 100644
--- a/include/linux/kd.h
+++ b/include/linux/kd.h
@@ -81,6 +81,7 @@ struct unimapinit {
#define K_XLATE 0x01
#define K_MEDIUMRAW 0x02
#define K_UNICODE 0x03
+#define K_OFF 0x04
#define KDGKBMODE 0x4B44 /* gets current keyboard mode */
#define KDSKBMODE 0x4B45 /* sets current keyboard mode */

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