[ARM] 3018/1: S3C2410 - check de-referenced device is really a platform device

Patch from Ben Dooks

Check that the device we are looking at is really
a platform device before trying to cast it to one
to find out the platform bus number.

Thanks to RMK for pointing this out.

Signed-off-by: Ben Dooks <ben-linux@fluff.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
diff --git a/arch/arm/mach-s3c2410/clock.c b/arch/arm/mach-s3c2410/clock.c
index f596082..8b3d5dc 100644
--- a/arch/arm/mach-s3c2410/clock.c
+++ b/arch/arm/mach-s3c2410/clock.c
@@ -98,7 +98,10 @@
 	struct clk *clk = ERR_PTR(-ENOENT);
 	int idno;
 
-	idno = (dev == NULL) ? -1 : to_platform_device(dev)->id;
+	if (dev == NULL || dev->bus != &platform_bus_type)
+		idno = -1;
+	else
+		idno = to_platform_device(dev)->id;
 
 	down(&clocks_sem);