Re: Magic Alt-SysRq change in 2.6.18-rc1
- From: Andrew Morton <akpm@xxxxxxxx>
- Date: Sun, 9 Jul 2006 17:22:22 -0700
On Sun, 9 Jul 2006 17:06:57 -0400 (EDT)
Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote:
Dmitry:
Are you the right person to handle changes in the behavior of Alt-SysRq?
Before 2.6.18-rc1, I used to be able to use it as follows:
Press and hold an Alt key,
Press and hold the SysRq key,
Release the Alt key,
Press and release some hot key like S or T or 7,
Repeat the previous step as many times as desired,
Release the SysRq key.
This scheme doesn't work any more, or if it does, the timing requirements
are now much stricter. In practice I have to hold down all three keys at
the same time; I can't release the Alt key before pressing the hot key.
This makes thinks very awkward on my laptop machine. Its keyboard
controller doesn't seem to like having three keys pressed simultaneously.
Instead of the expected hotkey behavior, I usually got an error message
from atkbd warning about too many keys being pressed. Getting it to work
as desired is hit-and-miss.
I would really appreciate going back to the old behavior, where only two
keys needed to be held down at any time.
I assume reverting the below will fix it?
From: Fredrik Roubert <roubert@xxxxxxxxx>
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@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxx>
---
drivers/char/keyboard.c | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)
diff -puN drivers/char/keyboard.c~fix-magic-sysrq-on-strange-keyboards drivers/char/keyboard.c
--- a/drivers/char/keyboard.c~fix-magic-sysrq-on-strange-keyboards
+++ a/drivers/char/keyboard.c
@@ -151,6 +151,7 @@ unsigned char kbd_sysrq_xlate[KEY_MAX +
"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 key
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 key
#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;
_
-
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- References:
- Magic Alt-SysRq change in 2.6.18-rc1
- From: Alan Stern
- Magic Alt-SysRq change in 2.6.18-rc1
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