[media] rc-core: reuse device numbers

Before changeset d8b4b5822f51e, the remote controller device numbers
were released when the device were unregistered. That helped to maintain
some sanity, as, when USB devices are replugged, the remote controller
would get the same number.

Restore the same behaviour.

Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>

drivers/media/rc/rc-main.c

@@ -22,6 +22,10 @@
 #include <linux/module.h>
 #include "rc-core-priv.h"
 
+/* Bitmap to store allocated device numbers from 0 to IRRCV_NUM_DEVICES - 1 */
+#define IRRCV_NUM_DEVICES      256
+DECLARE_BITMAP(ir_core_dev_number, IRRCV_NUM_DEVICES);
+
 /* Sizes are in bytes, 256 bytes allows for 32 entries on x64 */
 #define IR_TAB_MIN_SIZE	256
 #define IR_TAB_MAX_SIZE	8192
@@ -1065,10 +1069,9 @@ EXPORT_SYMBOL_GPL(rc_free_device);
 int rc_register_device(struct rc_dev *dev)
 {
 	static bool raw_init = false; /* raw decoders loaded? */
-	static atomic_t devno = ATOMIC_INIT(0);
 	struct rc_map *rc_map;
 	const char *path;
-	int rc;
+	int rc, devno;
 
 	if (!dev || !dev->map_name)
 		return -EINVAL;
@@ -1096,7 +1099,15 @@ int rc_register_device(struct rc_dev *dev)
 	 */
 	mutex_lock(&dev->lock);
 
-	dev->devno = (unsigned long)(atomic_inc_return(&devno) - 1);
+	do {
+		devno = find_first_zero_bit(ir_core_dev_number,
+					    IRRCV_NUM_DEVICES);
+		/* No free device slots */
+		if (devno >= IRRCV_NUM_DEVICES)
+			return -ENOMEM;
+	} while (test_and_set_bit(devno, ir_core_dev_number));
+
+	dev->devno = devno;
 	dev_set_name(&dev->dev, "rc%ld", dev->devno);
 	dev_set_drvdata(&dev->dev, dev);
 	rc = device_add(&dev->dev);
@@ -1186,6 +1197,7 @@ out_dev:
 	device_del(&dev->dev);
 out_unlock:
 	mutex_unlock(&dev->lock);
+	clear_bit(dev->devno, ir_core_dev_number);
 	return rc;
 }
 EXPORT_SYMBOL_GPL(rc_register_device);
@@ -1197,6 +1209,8 @@ void rc_unregister_device(struct rc_dev *dev)
 
 	del_timer_sync(&dev->timer_keyup);
 
+	clear_bit(dev->devno, ir_core_dev_number);
+
 	if (dev->driver_type == RC_DRIVER_IR_RAW)
 		ir_raw_event_unregister(dev);