sysdev: detect multiple driver registrations

I've just found how easy it is to accidentally register a sysdev_driver for
two different classes.  When this happens, bad things happen as the
sysdev_driver structure keeps has the list entry for the driver
registration.

The following patch makes a WARN_ON() if this happens, although I think
BUG_ON or returning -EAGAIN could also be valid responses to this.

Signed-off-by: Ben Dooks <ben@fluff.org>
Cc: Kay Sievers <kay.sievers@vrfy.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/base/sys.c b/drivers/base/sys.c
index 8e13fd9421635753f7b634ba4177b5df003a074f..1a06c2393719e9022a57be10118b31421a1f0211 100644 (file)
--- a/drivers/base/sys.c
+++ b/drivers/base/sys.c
@@ -167,6 +167,22 @@ int sysdev_driver_register(struct sysdev_class *cls, struct sysdev_driver *drv)
 {
        int err = 0;
 
+       if (!cls) {
+               printk(KERN_WARNING "sysdev: invalid class passed to "
+                       "sysdev_driver_register!\n");
+               WARN_ON(1);
+               return -EINVAL;
+       }
+
+       /* Check whether this driver has already been added to a class. */
+       if ((drv->entry.next != drv->entry.prev) ||
+           (drv->entry.next != NULL)) {
+               printk(KERN_WARNING "sysdev: class %s: driver (%p) has already"
+                       " been registered to a class, something is wrong, but "
+                       "will forge on!\n", cls->name, drv);
+               WARN_ON(1);
+       }
+
        mutex_lock(&sysdev_drivers_lock);
        if (cls && kset_get(&cls->kset)) {
                list_add_tail(&drv->entry, &cls->drivers);