change SysRq keycode for systems without SysRq key

#ifdef CONFIG_MAGIC_SYSRQ /* Handle the SysRq Hack */

drivers/char/keyboard.c +1 -1

-	if (keycode == KEY_SYSRQ && (sysrq_down || (down == 1 && sysrq_alt))) {
+	if (keycode == CONFIG_MAGIC_SYSRQ_KEYCODE && (sysrq_down || (down == 1 && sysrq_alt))) {
 		sysrq_down = down;
 		return;
 	}

diff -uprN linux.orig/lib/Kconfig.debug linux/lib/Kconfig.debug

lib/Kconfig.debug +3 -0

@@ -28,6 +28,16 @@ config MAGIC_SYSRQ
 	  send a BREAK and then within 5 seconds a command keypress. The
 	  keys are documented in <file:Documentation/sysrq.txt>. Don't say Y
 	  unless you really know what this hack does.
+	  
+config MAGIC_SYSRQ_KEYCODE
+	int

Seems harmless enough ;)

Could you please send in a suitable update to Documentation/sysrq.txt?

Quoted 46 lines

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this patch adds an entry in Kconfig after 'config MAGIC_SYSRQ' which asks for a different keycode (replacing also KEY_SYSRQ with CONFIG_MAGIC_SYSRQ_KEYCODE in char/keyboard.c)

Federico

Quite frankly, I think that if we want to make something like this configurable, it should be dynamic, not compiled-in. So that the same kernel image can be used with different keyboards.

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Linus

(I can imagine it could be done via a /proc/sysrq-keycode virtual file, but that's just one possibility)

So, this should turn into a feature request...
would you accept feature requests? ( :

Federico

Well, this is totally untested, and I won't guarantee that this works at all, but this is how to generally do these kinds of things..

Linus

---
 drivers/char/keyboard.c |    6 +++++-
 1 files changed, 5 insertions(+), 1 deletions(-)

drivers/char/keyboard.c +3 -0

index 90965b4..e21f52b 100644
@@ -157,6 +157,10 @@ static int sysrq_alt_use;
 #endif
 static int sysrq_alt;
 >> +static int sysrq_key = KEY_SYSRQ;
+module_param_named(sysrq_key, sysrq_key, uint, 0644);
+MODULE_PARM_DESC(sysrq_key, "The keycode to be used for sysrq");
+
 /*
  * Translation of scancodes to keycodes. We set them on only the first
  * keyboard in the list that accepts the scancode and keycode.

@@ -1139,7 +1143,7 @@ static void kbd_keycode(unsigned int keycode, int down, int hw_raw)
                 printk(KERN_WARNING "keyboard.c: can't emulate rawmode for keycode %d\n", keycode);

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#ifdef CONFIG_MAGIC_SYSRQ /* Handle the SysRq Hack */

drivers/char/keyboard.c

Quoted 5 lines

drivers/char/keyboard.c +1 -1

-    if (keycode == KEY_SYSRQ && (sysrq_down || (down == 1 && sysrq_alt))) {
+    if (keycode == sysrq_key && (sysrq_down || (down == 1 && sysrq_alt))) {
         if (!sysrq_down) {
             sysrq_down = down;
             sysrq_alt_use = sysrq_alt;

YAY! it works great.
tried with:

# echo 183 > /sys/module/keyboard/parameters/sysrq_key
but also keyboard.sys_rq=183 on the command line should work; I'll
discover that on next reboot.

thank you, Linus!

(now that this has done in the proper way, is this patch going to be merged in the tree?)

Dmitry Torokhov ha scritto:

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Dmitry? Any reason not to do this?

Recent kernels have the ability to remap keymap for USB keyboards via EVIOCSKEYCODE ioctl (we allowed 0adjusting keymaps on PS/2 keyboards for a long time). So instead of having the new parameter redefining SysRq keycode Frederico can remap one of the keys on his keyboard to generate KEY_SYSRQ. This way SysRq should still work if he plugs in another USB keyboard that has SysRq key or a PS/2 keyboard.

would setkeycodes still just work for PS2 keyboards?
I upgraded to newer kbd-1.13 package (kernel 2.6.21), and while trying to change sysrq keycode still I get the old error:

KDSETKEYCODE: No such device
failed to set scancode 38b7 to keycode 84

which I reported on gentoo a long time ago:
http://bugs.gentoo.org/show_bug.cgi?id=97388

(it doesn't use EVIOCSKEYCODE)
maybe I'm not picking up the right program?