[PATCH v3] rtc: add devm_rtc_device_{register,unregister}()

[Jingoo Han]

These functios allows the driver core to automatically clean up
any allocation made by rtc drivers. Thus, it simplifies the error
paths.

Signed-off-by: Jingoo Han <jg1.han@xxxxxxxxxxx>
---
Changes since v2:
- Removed unnecessary WARN_ON() of devm_rtc_device_match()

Changes since v1:
- Simplified 'if' statements using WARN_ON()
- Added a description of the return value of devm_rtc_device_register()

 drivers/rtc/class.c |   70 +++++++++++++++++++++++++++++++++++++++++++++++++++
 include/linux/rtc.h |    6 ++++
 2 files changed, 76 insertions(+), 0 deletions(-)

diff --git a/drivers/rtc/class.c b/drivers/rtc/class.c
index 9b742d3..b72b40b 100644
--- a/drivers/rtc/class.c
+++ b/drivers/rtc/class.c
@@ -259,6 +259,76 @@ void rtc_device_unregister(struct rtc_device *rtc)
 }
 EXPORT_SYMBOL_GPL(rtc_device_unregister);
 
+static void devm_rtc_device_release(struct device *dev, void *res)
+{
+	struct rtc_device *rtc = *(struct rtc_device **)res;
+
+	rtc_device_unregister(rtc);
+}
+
+static int devm_rtc_device_match(struct device *dev, void *res, void *data)
+{
+	struct rtc **r = res;
+
+	return *r == data;
+}
+
+/**
+ * devm_rtc_device_register - resource managed rtc_device_register()
+ * @name: the name of the device
+ * @dev: the device to register
+ * @ops: the rtc operations structure
+ * @owner: the module owner
+ *
+ * @return a struct rtc on success, or an ERR_PTR on error
+ *
+ * Managed rtc_device_register(). The rtc_device returned from this function
+ * are automatically freed on driver detach. See rtc_device_register()
+ * for more information.
+ */
+
+struct rtc_device *devm_rtc_device_register(const char *name,
+					struct device *dev,
+					const struct rtc_class_ops *ops,
+					struct module *owner)
+{
+	struct rtc_device **ptr, *rtc;
+
+	ptr = devres_alloc(devm_rtc_device_release, sizeof(*ptr), GFP_KERNEL);
+	if (!ptr)
+		return ERR_PTR(-ENOMEM);
+
+	rtc = rtc_device_register(name, dev, ops, owner);
+	if (!IS_ERR(rtc)) {
+		*ptr = rtc;
+		devres_add(dev, ptr);
+	} else {
+		devres_free(ptr);
+	}
+
+	return rtc;
+}
+EXPORT_SYMBOL_GPL(devm_rtc_device_register);
+
+/**
+ * devm_rtc_device_unregister - resource managed devm_rtc_device_unregister()
+ * @dev: the device to unregister
+ * @rtc: the RTC class device to unregister
+ *
+ * Deallocated a rtc allocated with devm_rtc_device_register(). Normally this
+ * function will not need to be called and the resource management code will
+ * ensure that the resource is freed.
+ */
+void devm_rtc_device_unregister(struct device *dev, struct rtc_device *rtc)
+{
+	int rc;
+
+	rc = devres_release(dev, devm_rtc_device_release,
+				devm_rtc_device_match, rtc);
+	WARN_ON(rc);
+}
+EXPORT_SYMBOL_GPL(devm_rtc_device_unregister);
+
 static int __init rtc_init(void)
 {
 	rtc_class = class_create(THIS_MODULE, "rtc");
diff --git a/include/linux/rtc.h b/include/linux/rtc.h
index 580b24c..d955768 100644
--- a/include/linux/rtc.h
+++ b/include/linux/rtc.h
@@ -133,7 +133,13 @@ extern struct rtc_device *rtc_device_register(const char *name,
 					struct device *dev,
 					const struct rtc_class_ops *ops,
 					struct module *owner);
+extern struct rtc_device *devm_rtc_device_register(const char *name,
+					struct device *dev,
+					const struct rtc_class_ops *ops,
+					struct module *owner);
 extern void rtc_device_unregister(struct rtc_device *rtc);
+extern void devm_rtc_device_unregister(struct device *dev,
+					struct rtc_device *rtc);
 
 extern int rtc_read_time(struct rtc_device *rtc, struct rtc_time *tm);
 extern int rtc_set_time(struct rtc_device *rtc, struct rtc_time *tm);
-- 
1.7.2.5


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