hwmon: convert idr to ida and use ida_simple interface

hwmon was using an idr with a NULL pointer, so convert to an
ida which then allows use of Rusty's ida_simple_get.
Signed-off-by: Jonathan Cameron <jic23@cam.ac.uk>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Tejun Heo <tj@kernel.org>
Acked-by: Guenter Roeck <guenter.roeck@ericsson.com>
Cc: James Bottomley <James.Bottomley@HansenPartnership.com>
Cc: David Airlie <airlied@linux.ie>
Cc: Thomas Hellstrom <thellstrom@vmware.com>
Cc: Evgeniy Polyakov <zbr@ioremap.net>
Cc: Darrick J. Wong <djwong@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/hwmon/hwmon.c

@@ -27,8 +27,7 @@
 
 static struct class *hwmon_class;
 
-static DEFINE_IDR(hwmon_idr);
-static DEFINE_SPINLOCK(idr_lock);
+static DEFINE_IDA(hwmon_ida);
 
 /**
  * hwmon_device_register - register w/ hwmon
@@ -42,30 +41,17 @@ static DEFINE_SPINLOCK(idr_lock);
 struct device *hwmon_device_register(struct device *dev)
 {
 	struct device *hwdev;
-	int id, err;
-
-again:
-	if (unlikely(idr_pre_get(&hwmon_idr, GFP_KERNEL) == 0))
-		return ERR_PTR(-ENOMEM);
-
-	spin_lock(&idr_lock);
-	err = idr_get_new(&hwmon_idr, NULL, &id);
-	spin_unlock(&idr_lock);
+	int id;
 
-	if (unlikely(err == -EAGAIN))
-		goto again;
-	else if (unlikely(err))
-		return ERR_PTR(err);
+	id = ida_simple_get(&hwmon_ida, 0, 0, GFP_KERNEL);
+	if (id < 0)
+		return ERR_PTR(id);
 
-	id = id & MAX_ID_MASK;
 	hwdev = device_create(hwmon_class, dev, MKDEV(0, 0), NULL,
 			      HWMON_ID_FORMAT, id);
 
-	if (IS_ERR(hwdev)) {
-		spin_lock(&idr_lock);
-		idr_remove(&hwmon_idr, id);
-		spin_unlock(&idr_lock);
-	}
+	if (IS_ERR(hwdev))
+		ida_simple_remove(&hwmon_ida, id);
 
 	return hwdev;
 }
@@ -81,9 +67,7 @@ void hwmon_device_unregister(struct device *dev)
 
 	if (likely(sscanf(dev_name(dev), HWMON_ID_FORMAT, &id) == 1)) {
 		device_unregister(dev);
-		spin_lock(&idr_lock);
-		idr_remove(&hwmon_idr, id);
-		spin_unlock(&idr_lock);
+		ida_simple_remove(&hwmon_ida, id);
 	} else
 		dev_dbg(dev->parent,
 			"hwmon_device_unregister() failed: bad class ID!\n");