drivers/rtc/class.c: convert idr to ida and use ida_simple_get()

This is the one use of an ida that doesn't retry on receiving -EAGAIN.
I'm assuming do so will cause no harm and may help on a rare occasion.
Signed-off-by: Jonathan Cameron <jic23@cam.ac.uk>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/rtc/class.c

@@ -21,16 +21,13 @@
 #include "rtc-core.h"
 
 
-static DEFINE_IDR(rtc_idr);
-static DEFINE_MUTEX(idr_lock);
+static DEFINE_IDA(rtc_ida);
 struct class *rtc_class;
 
 static void rtc_device_release(struct device *dev)
 {
 	struct rtc_device *rtc = to_rtc_device(dev);
-	mutex_lock(&idr_lock);
-	idr_remove(&rtc_idr, rtc->id);
-	mutex_unlock(&idr_lock);
+	ida_simple_remove(&rtc_ida, rtc->id);
 	kfree(rtc);
 }
 
@@ -146,25 +143,16 @@ struct rtc_device *rtc_device_register(const char *name, struct device *dev,
 	struct rtc_wkalrm alrm;
 	int id, err;
 
-	if (idr_pre_get(&rtc_idr, GFP_KERNEL) == 0) {
-		err = -ENOMEM;
+	id = ida_simple_get(&rtc_ida, 0, 0, GFP_KERNEL);
+	if (id < 0) {
+		err = id;
 		goto exit;
 	}
 
-
-	mutex_lock(&idr_lock);
-	err = idr_get_new(&rtc_idr, NULL, &id);
-	mutex_unlock(&idr_lock);
-
-	if (err < 0)
-		goto exit;
-
-	id = id & MAX_ID_MASK;
-
 	rtc = kzalloc(sizeof(struct rtc_device), GFP_KERNEL);
 	if (rtc == NULL) {
 		err = -ENOMEM;
-		goto exit_idr;
+		goto exit_ida;
 	}
 
 	rtc->id = id;
@@ -222,10 +210,8 @@ struct rtc_device *rtc_device_register(const char *name, struct device *dev,
 exit_kfree:
 	kfree(rtc);
 
-exit_idr:
-	mutex_lock(&idr_lock);
-	idr_remove(&rtc_idr, id);
-	mutex_unlock(&idr_lock);
+exit_ida:
+	ida_simple_remove(&rtc_ida, id);
 
 exit:
 	dev_err(dev, "rtc core: unable to register %s, err = %d\n",
@@ -276,7 +262,7 @@ static void __exit rtc_exit(void)
 {
 	rtc_dev_exit();
 	class_destroy(rtc_class);
-	idr_destroy(&rtc_idr);
+	ida_destroy(&rtc_ida);
 }
 
 subsys_initcall(rtc_init);