iio: buffer-dmaengine: add dev-managed calls for buffer alloc

Currently, when using a 'iio_dmaengine_buffer_alloc()', an matching call to
'iio_dmaengine_buffer_free()' must be made.

With this change, this can be avoided by using
'devm_iio_dmaengine_buffer_alloc()'. The buffer will get free'd via the
device's devres handling.
Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/buffer/industrialio-buffer-dmaengine.c

@@ -229,6 +229,45 @@ void iio_dmaengine_buffer_free(struct iio_buffer *buffer)
 }
 EXPORT_SYMBOL_GPL(iio_dmaengine_buffer_free);
 
+static void __devm_iio_dmaengine_buffer_free(struct device *dev, void *res)
+{
+	iio_dmaengine_buffer_free(*(struct iio_buffer **)res);
+}
+
+/**
+ * devm_iio_dmaengine_buffer_alloc() - Resource-managed iio_dmaengine_buffer_alloc()
+ * @dev: Parent device for the buffer
+ * @channel: DMA channel name, typically "rx".
+ *
+ * This allocates a new IIO buffer which internally uses the DMAengine framework
+ * to perform its transfers. The parent device will be used to request the DMA
+ * channel.
+ *
+ * The buffer will be automatically de-allocated once the device gets destroyed.
+ */
+struct iio_buffer *devm_iio_dmaengine_buffer_alloc(struct device *dev,
+	const char *channel)
+{
+	struct iio_buffer **bufferp, *buffer;
+
+	bufferp = devres_alloc(__devm_iio_dmaengine_buffer_free,
+			       sizeof(*bufferp), GFP_KERNEL);
+	if (!bufferp)
+		return ERR_PTR(-ENOMEM);
+
+	buffer = iio_dmaengine_buffer_alloc(dev, channel);
+	if (IS_ERR(buffer)) {
+		devres_free(bufferp);
+		return buffer;
+	}
+
+	*bufferp = buffer;
+	devres_add(dev, bufferp);
+
+	return buffer;
+}
+EXPORT_SYMBOL_GPL(devm_iio_dmaengine_buffer_alloc);
+
 MODULE_AUTHOR("Lars-Peter Clausen <lars@metafoo.de>");
 MODULE_DESCRIPTION("DMA buffer for the IIO framework");
 MODULE_LICENSE("GPL");

include/linux/iio/buffer-dmaengine.h

@@ -14,4 +14,7 @@ struct iio_buffer *iio_dmaengine_buffer_alloc(struct device *dev,
 	const char *channel);
 void iio_dmaengine_buffer_free(struct iio_buffer *buffer);
 
+struct iio_buffer *devm_iio_dmaengine_buffer_alloc(struct device *dev,
+						   const char *channel);
+
 #endif