kernel/reboot.c: add devm_register_reboot_notifier()

Add devm_* wrapper around register_reboot_notifier to simplify device
specific reboot notifier registration/unregistration.

[[e-mail]: move `struct device' forward decl to top-of-file]
Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: Andrey Smirnov <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

include/linux/reboot.h

···
 #include <linux/notifier.h>
 #include <uapi/linux/reboot.h>
 
+struct device;
+
 #define SYS_DOWN	0x0001	/* Notify of system down */
 #define SYS_RESTART	SYS_DOWN
 #define SYS_HALT	0x0002	/* Notify of system halt */
···
 
 extern int register_reboot_notifier(struct notifier_block *);
 extern int unregister_reboot_notifier(struct notifier_block *);
+
+extern int devm_register_reboot_notifier(struct device *, struct notifier_block *);
 
 extern int register_restart_handler(struct notifier_block *);
 extern int unregister_restart_handler(struct notifier_block *);

kernel/reboot.c

···
 }
 EXPORT_SYMBOL(unregister_reboot_notifier);
 
+static void devm_unregister_reboot_notifier(struct device *dev, void *res)
+{
+	WARN_ON(unregister_reboot_notifier(*(struct notifier_block **)res));
+}
+
+int devm_register_reboot_notifier(struct device *dev, struct notifier_block *nb)
+{
+	struct notifier_block **rcnb;
+	int ret;
+
+	rcnb = devres_alloc(devm_unregister_reboot_notifier,
+			    sizeof(*rcnb), GFP_KERNEL);
+	if (!rcnb)
+		return -ENOMEM;
+
+	ret = register_reboot_notifier(nb);
+	if (!ret) {
+		*rcnb = nb;
+		devres_add(dev, rcnb);
+	} else {
+		devres_free(rcnb);
+	}
+
+	return ret;
+}
+EXPORT_SYMBOL(devm_register_reboot_notifier);
+
 /*
  *	Notifier list for kernel code which wants to be called
  *	to restart the system.