Re: [patch] Re: Magic Alt-SysRq change in 2.6.18-rc1

[Paulo Marques <pmarques@grupopie.com>]

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Roman Zippel wrote:
> On Tue, 11 Jul 2006, Andrew Morton wrote:
> [...]
>> What, actually, is the problem?
> 
> It changes the behaviour, it will annoy the hell out of people like me who 
> have to deal with different kernels and expect this to just work. :-(
> Since then has it been acceptable to just go ahead and break stuff? This 
> problem doesn't really look unsolvable, so why is my request to fix the 
> damn thing so unreasonable?

Ok, what about this one?

I don't have time to test it (it compiles, at least), but it seems the 
logic is pretty clear: once you have pressed both "Alt" and "SysRq" 
sysrq mode becomes active until you release *both* keys. In this mode 
any regular key press triggers handle_sysrq.

This allows for all the combinations mentioned before in this thread and 
makes the logic simpler, IMHO.

-- 
Paulo Marques - www.grupopie.com

Pointy-Haired Boss: I don't see anything that could stand in our way.
            Dilbert: Sanity? Reality? The laws of physics?

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Subject: allow the old behavior of Alt+SysRq+<key>

This should allow any order of Alt + SysRq press followed by any key
while still holding one of SysRq or Alt.

Signed-off-by: Paulo Marques <pmarques@grupopie.com>

--- ./drivers/char/keyboard.c.orig	2006-07-12 13:03:32.000000000 +0100
+++ ./drivers/char/keyboard.c	2006-07-12 14:18:52.000000000 +0100
@@ -150,7 +150,7 @@ 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;
+static int sysrq_active;
 #endif
 static int sysrq_alt;

@@ -1164,16 +1164,17 @@ static void kbd_keycode(unsigned int key
 				printk(KERN_WARNING "keyboard.c: can't emulate rawmode for keycode %d\n", keycode);

 #ifdef CONFIG_MAGIC_SYSRQ	       /* Handle the SysRq Hack */
-	if (keycode == KEY_SYSRQ && (sysrq_down || (down == 1 && sysrq_alt))) {
-		if (!sysrq_down) {
-			sysrq_down = down;
-			sysrq_alt_use = sysrq_alt;
-		}
+	if (keycode == KEY_SYSRQ) {
+		sysrq_down = down;
 		return;
 	}
-	if (sysrq_down && !down && keycode == sysrq_alt_use)
-		sysrq_down = 0;
-	if (sysrq_down && down && !rep) {
+
+	if (sysrq_down && sysrq_alt)
+		sysrq_active = 1;
+	else if (!sysrq_down && !sysrq_alt)
+		sysrq_active = 0;
+
+	if (sysrq_active && down && !rep) {
 		handle_sysrq(kbd_sysrq_xlate[keycode], regs, tty);
 		return;
 	}