iio: core: Implement devm_iio_device_{register,unregister}

Add device managed devm_iio_device_{register,unregister}()
to automatically unregister IIO drivers thus leading to
simplified IIO driver code.
Signed-off-by: Sachin Kamat <sachin.kamat@linaro.org>
Cc: Lars-Peter Clausen <lars@metafoo.de>
Tested-by: Lars-Peter Clausen <lars@metafoo.de>
Reviewed-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

Documentation/driver-model/devres.txt

@@ -242,6 +242,8 @@ IIO
   devm_iio_device_free()
   devm_iio_trigger_alloc()
   devm_iio_trigger_free()
+  devm_iio_device_register()
+  devm_iio_device_unregister()
 
 IO region
   devm_request_region()

drivers/iio/industrialio-core.c

@@ -1161,6 +1161,65 @@ void iio_device_unregister(struct iio_dev *indio_dev)
 	mutex_unlock(&indio_dev->info_exist_lock);
 }
 EXPORT_SYMBOL(iio_device_unregister);
+
+static void devm_iio_device_unreg(struct device *dev, void *res)
+{
+	iio_device_unregister(*(struct iio_dev **)res);
+}
+
+/**
+ * devm_iio_device_register - Resource-managed iio_device_register()
+ * @dev:	Device to allocate iio_dev for
+ * @indio_dev:	Device structure filled by the device driver
+ *
+ * Managed iio_device_register.  The IIO device registered with this
+ * function is automatically unregistered on driver detach. This function
+ * calls iio_device_register() internally. Refer to that function for more
+ * information.
+ *
+ * If an iio_dev registered with this function needs to be unregistered
+ * separately, devm_iio_device_unregister() must be used.
+ *
+ * RETURNS:
+ * 0 on success, negative error number on failure.
+ */
+int devm_iio_device_register(struct device *dev, struct iio_dev *indio_dev)
+{
+	struct iio_dev **ptr;
+	int ret;
+
+	ptr = devres_alloc(devm_iio_device_unreg, sizeof(*ptr), GFP_KERNEL);
+	if (!ptr)
+		return -ENOMEM;
+
+	*ptr = indio_dev;
+	ret = iio_device_register(indio_dev);
+	if (!ret)
+		devres_add(dev, ptr);
+	else
+		devres_free(ptr);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(devm_iio_device_register);
+
+/**
+ * devm_iio_device_unregister - Resource-managed iio_device_unregister()
+ * @dev:	Device this iio_dev belongs to
+ * @indio_dev:	the iio_dev associated with the device
+ *
+ * Unregister iio_dev registered with devm_iio_device_register().
+ */
+void devm_iio_device_unregister(struct device *dev, struct iio_dev *indio_dev)
+{
+	int rc;
+
+	rc = devres_release(dev, devm_iio_device_unreg,
+			    devm_iio_device_match, indio_dev);
+	WARN_ON(rc);
+}
+EXPORT_SYMBOL_GPL(devm_iio_device_unregister);
+
 subsys_initcall(iio_init);
 module_exit(iio_exit);
 

include/linux/iio/iio.h

@@ -510,6 +510,9 @@ int iio_device_register(struct iio_dev *indio_dev);
  **/
 void iio_device_unregister(struct iio_dev *indio_dev);
 
+int devm_iio_device_register(struct device *dev, struct iio_dev *indio_dev);
+void devm_iio_device_unregister(struct device *dev, struct iio_dev *indio_dev);
+
 /**
  * iio_push_event() - try to add event to the list for userspace reading
  * @indio_dev:		IIO device structure