HWRNG: add possibility to remove hwrng devices during suspend/resume

Make it possible to unregister a Hardware Random Number Generator
device object in a safe way during a suspend/resume cycle.
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Acked-by: Michael Buesch <mb@bu3sch.de>
Cc: Michael Buesch <mb@bu3sch.de>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: "John W. Linville" <linville@tuxdriver.com>
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: Len Brown <lenb@kernel.org>
Cc: Greg KH <greg@kroah.com>
Cc: Kay Sievers <kay.sievers@vrfy.org>
Cc: Richard Purdie <rpurdie@rpsys.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/char/hw_random/core.c

@@ -234,11 +234,11 @@ static DEVICE_ATTR(rng_available, S_IRUGO,
 		   NULL);
 
 
-static void unregister_miscdev(void)
+static void unregister_miscdev(bool suspended)
 {
 	device_remove_file(rng_miscdev.this_device, &dev_attr_rng_available);
 	device_remove_file(rng_miscdev.this_device, &dev_attr_rng_current);
-	misc_deregister(&rng_miscdev);
+	__misc_deregister(&rng_miscdev, suspended);
 }
 
 static int register_miscdev(void)
@@ -313,7 +313,7 @@ int hwrng_register(struct hwrng *rng)
 }
 EXPORT_SYMBOL_GPL(hwrng_register);
 
-void hwrng_unregister(struct hwrng *rng)
+void __hwrng_unregister(struct hwrng *rng, bool suspended)
 {
 	int err;
 
@@ -332,11 +332,11 @@ void hwrng_unregister(struct hwrng *rng)
 		}
 	}
 	if (list_empty(&rng_list))
-		unregister_miscdev();
+		unregister_miscdev(suspended);
 
 	mutex_unlock(&rng_mutex);
 }
-EXPORT_SYMBOL_GPL(hwrng_unregister);
+EXPORT_SYMBOL_GPL(__hwrng_unregister);
 
 
 MODULE_DESCRIPTION("H/W Random Number Generator (RNG) driver");

include/linux/hw_random.h

@@ -44,7 +44,15 @@ struct hwrng {
 /** Register a new Hardware Random Number Generator driver. */
 extern int hwrng_register(struct hwrng *rng);
 /** Unregister a Hardware Random Number Generator driver. */
-extern void hwrng_unregister(struct hwrng *rng);
+extern void __hwrng_unregister(struct hwrng *rng, bool suspended);
+static inline void hwrng_unregister(struct hwrng *rng)
+{
+	__hwrng_unregister(rng, false);
+}
+static inline void hwrng_unregister_suspended(struct hwrng *rng)
+{
+	__hwrng_unregister(rng, true);
+}
 
 #endif /* __KERNEL__ */
 #endif /* LINUX_HWRANDOM_H_ */