[patch-2.4.2-ac8] misc_register() fix (was Re: Linux 2.4.2ac8

[Tigran Aivazian]

On Fri, 2 Mar 2001, Tigran Aivazian wrote:
> On Thu, 1 Mar 2001, Alan Cox wrote:
> > 2.4.2-ac8
> > o	Stop two people claiming the same misc dev id	(Philipp Rumpf)
> 
> is this what has broken misc devi registration on my machine? I have two
> misc devices -- microcode and psaux -- now (ac8) I get none, /proc/misc is
> empty. Also, on boot gpm generates an "oops" from gpm.c(968) saying
> "/dev/mouse: No such device"

Hi Alan,

here is the fix, tested, it works fine. The only unsatisfactory thing is
that we do an extra if() on each iteration making misc_register()
typically a few instructions slower. I will think a few minutes on how to
make the old version work (i.e. I suspect it was just an incorrect walking
of the misc_list in ac8).

Regards,
Tigran

--- linux/drivers/char/misc.c.0	Fri Mar  2 09:35:01 2001
+++ linux/drivers/char/misc.c	Fri Mar  2 10:01:17 2001
@@ -175,14 +175,16 @@
 	
 	if (misc->next || misc->prev)
 		return -EBUSY;
+
 	down(&misc_sem);
-	c = misc_list.next;
 
-	while ((c != &misc_list) && (c->minor != misc->minor))
+	c = misc_list.next;
+	while (c != &misc_list) {
+		if (c->minor == misc->minor) {
+			up(&misc_sem);
+			return -EBUSY;
+		}
 		c = c->next;
-	if (c == &misc_list) {
-		up(&misc_sem);
-		return -EBUSY;
 	}
 
 	if (misc->minor == MISC_DYNAMIC_MINOR) {