[PATCH] fix magic sysrq on strange keyboards

Magic sysrq fails to work on many keyboards, particulary most of notebook
keyboards.  This patch fixes it.

The idea is quite simple: Discard the SysRq break code if Alt is still being
held down.  This way the broken keyboard can send the break code (or the user
with a normal keyboard can release the SysRq key) and the kernel waits until
the next key is pressed or the Alt key is released.

Signed-off-by: Pavel Machek <pavel@suse.cz>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 8 insertions, 2 deletions

diff --git a/drivers/char/keyboard.c b/drivers/char/keyboard.c
index edd996f6fb87..13e3126c1de5 100644
--- a/drivers/char/keyboard.c
+++ b/drivers/char/keyboard.c
@@ -151,6 +151,7 @@ unsigned char kbd_sysrq_xlate[KEY_MAX + 1] =
         "230\177\000\000\213\214\000\000\000\000\000\000\000\000\000\000" /* 0x50 - 0x5f */
         "\r\000/";                                      /* 0x60 - 0x6f */
 static int sysrq_down;
+static int sysrq_alt_use;
 #endif
 static int sysrq_alt;
 
@@ -1143,7 +1144,7 @@ static void kbd_keycode(unsigned int keycode, int down,
         kbd = kbd_table + fg_console;
 
         if (keycode == KEY_LEFTALT || keycode == KEY_RIGHTALT)
-                sysrq_alt = down;
+                sysrq_alt = down ? keycode : 0;
 #ifdef CONFIG_SPARC
         if (keycode == KEY_STOP)
                 sparc_l1_a_state = down;
@@ -1163,9 +1164,14 @@ static void kbd_keycode(unsigned int keycode, int down,
 
 #ifdef CONFIG_MAGIC_SYSRQ              /* Handle the SysRq Hack */
         if (keycode == KEY_SYSRQ && (sysrq_down || (down == 1 && sysrq_alt))) {
-                sysrq_down = down;
+                if (!sysrq_down) {
+                        sysrq_down = down;
+                        sysrq_alt_use = sysrq_alt;
+                }
                 return;
         }
+        if (sysrq_down && !down && keycode == sysrq_alt_use)
+                sysrq_down = 0;
         if (sysrq_down && down && !rep) {
                 handle_sysrq(kbd_sysrq_xlate[keycode], regs, tty);
                 return;