Staging: Panel: prevent driver from calling misc_deregister twice on same ressource

This patch prevents the driver from calling misc_deregister twice on the same
ressouce when unloading the driver.
Unloading the driver without this patch results in a Kernel BUG like this:
Panel driver version 0.9.5 registered on parport0 (io=0x378).
BUG: unable to handle kernel paging request at 0000000000100108
IP: [<ffffffff803c02ee>] misc_deregister+0x2d/0x90
PGD 6caff067 PUD 762b7067 PMD 0
Oops: 0002 [#1] PREEMPT SMP
last sysfs file: /sys/devices/platform/w83627hf.656/in8_input
...

This patch fixes this issue, although maybe not in the best way possible :)

linux version v2.6.32-rc1 - linus git tree, Di 29. Sep 01:10:18 CEST 2009

Signed-off-by: Peter Huewe <peterhuewe@gmx.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/staging/panel/panel.c

@@ -2071,11 +2071,15 @@ static void panel_detach(struct parport *port)
 		return;
 	}
 
-	if (keypad_enabled && keypad_initialized)
+	if (keypad_enabled && keypad_initialized) {
 		misc_deregister(&keypad_dev);
+		keypad_initialized = 0;
+	}
 
-	if (lcd_enabled && lcd_initialized)
+	if (lcd_enabled && lcd_initialized) {
 		misc_deregister(&lcd_dev);
+		lcd_initialized = 0;
+	}
 
 	parport_release(pprt);
 	parport_unregister_device(pprt);
@@ -2211,13 +2215,16 @@ static void __exit panel_cleanup_module(void)
 		del_timer(&scan_timer);
 
 	if (pprt != NULL) {
-		if (keypad_enabled)
+		if (keypad_enabled) {
 			misc_deregister(&keypad_dev);
+			keypad_initialized = 0;
+		}
 
 		if (lcd_enabled) {
 			panel_lcd_print("\x0cLCD driver " PANEL_VERSION
 					"\nunloaded.\x1b[Lc\x1b[Lb\x1b[L-");
 			misc_deregister(&lcd_dev);
+			lcd_initialized = 0;
 		}
 
 		/* TODO: free all input signals */