[PATCH] cdev_init: zero out cdev before kobject_init()

[PATCH] cdev_init: zero out cdev before kobject_init()

[Roland Dreier]

Right now, cdev_init() works in a way that is not very intuitive.  If
a driver passes an uninitialized struct cdev to cdev_init(), then an
uninitialized struct kobject will be passed to kobject_init(), which
does kset_get() on kobj->kset, which probably points off into space
and causes an oops.  Drivers can work around this by zeroing out their
struct cdev in advance (and indeed most if not all of the things
passed to cdev_init() come from BSS) but I think it makes more sense
for cdev_init() to live up to its name and actually work on an
uninitialized cdev.

Signed-off-by: Roland Dreier <roland@topspin.com>

Index: x/fs/char_dev.c
===================================================================
--- x.orig/fs/char_dev.c	2004-11-14 17:02:48.000000000 -0800
+++ x/fs/char_dev.c	2004-11-14 17:03:39.000000000 -0800
@@ -417,6 +417,7 @@
 
 void cdev_init(struct cdev *cdev, struct file_operations *fops)
 {
+	memset(cdev, 0, sizeof *cdev);	
 	INIT_LIST_HEAD(&cdev->list);
 	cdev->kobj.ktype = &ktype_cdev_default;
 	kobject_init(&cdev->kobj);