Subject: [patch] xen vt runtime


From: Ian Pratt <Ian.Pratt@cl.cam.ac.uk>

This patch enables the VT console to be disabled at runtime even if it is
built into the kernel.  Arch xen needs this to avoid trying to initialise a VT
in virtual machine that doesn't have access to the console hardware.

Signed-off-by: Ian Pratt <Ian.Pratt@cl.cam.ac.uk>
Signed-off-by: Andrew Morton <akpm@osdl.org>

Signed-off-by: Gerd Knorr <kraxel@bytesex.org>
Index: linux-2.6.11/drivers/char/tty_io.c
===================================================================
--- linux-2.6.11.orig/drivers/char/tty_io.c	2005-04-19 14:37:57.000000000 +0200
+++ linux-2.6.11/drivers/char/tty_io.c	2005-04-19 14:39:08.000000000 +0200
@@ -131,6 +131,8 @@ LIST_HEAD(tty_drivers);			/* linked list
    vt.c for deeply disgusting hack reasons */
 DECLARE_MUTEX(tty_sem);
 
+int console_use_vt = 1;
+
 #ifdef CONFIG_UNIX98_PTYS
 extern struct tty_driver *ptm_driver;	/* Unix98 pty masters; for /dev/ptmx */
 extern int pty_limit;		/* Config limit on Unix98 ptys */
@@ -1788,7 +1790,7 @@ retry_open:
 		goto got_driver;
 	}
 #ifdef CONFIG_VT
-	if (device == MKDEV(TTY_MAJOR,0)) {
+	if (console_use_vt && device == MKDEV(TTY_MAJOR,0)) {
 		extern int fg_console;
 		extern struct tty_driver *console_driver;
 		driver = console_driver;
@@ -2967,14 +2969,19 @@ static int __init tty_init(void)
 #endif
 
 #ifdef CONFIG_VT
-	cdev_init(&vc0_cdev, &console_fops);
-	if (cdev_add(&vc0_cdev, MKDEV(TTY_MAJOR, 0), 1) ||
-	    register_chrdev_region(MKDEV(TTY_MAJOR, 0), 1, "/dev/vc/0") < 0)
-		panic("Couldn't register /dev/tty0 driver\n");
-	devfs_mk_cdev(MKDEV(TTY_MAJOR, 0), S_IFCHR|S_IRUSR|S_IWUSR, "vc/0");
-	class_simple_device_add(tty_class, MKDEV(TTY_MAJOR, 0), NULL, "tty0");
+	if (console_use_vt) {
+		cdev_init(&vc0_cdev, &console_fops);
+		if (cdev_add(&vc0_cdev, MKDEV(TTY_MAJOR, 0), 1) ||
+		    register_chrdev_region(MKDEV(TTY_MAJOR, 0), 1,
+					   "/dev/vc/0") < 0)
+			panic("Couldn't register /dev/tty0 driver\n");
+		devfs_mk_cdev(MKDEV(TTY_MAJOR, 0), S_IFCHR|S_IRUSR|S_IWUSR,
+			      "vc/0");
+		class_simple_device_add(tty_class, MKDEV(TTY_MAJOR, 0), NULL,
+					"tty0");
 
-	vty_init();
+		vty_init();
+	}
 #endif
 	return 0;
 }