iio: buffer-dmaengine: add devm_iio_dmaengine_buffer_setup_with_handle()

Add a new devm_iio_dmaengine_buffer_setup_with_handle() function to
handle cases where the DMA channel is managed by the caller rather than
being requested and released by the iio_dmaengine module.

Reviewed-by: Nuno Sa <[e-mail]>
Signed-off-by: David Lechner <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Jonathan Cameron <[e-mail]>

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

···
 }
 EXPORT_SYMBOL_NS_GPL(devm_iio_dmaengine_buffer_setup_ext, "IIO_DMAENGINE_BUFFER");
 
+static void devm_iio_dmaengine_buffer_free(void *buffer)
+{
+	iio_dmaengine_buffer_free(buffer);
+}
+
+/**
+ * devm_iio_dmaengine_buffer_setup_with_handle() - Setup a DMA buffer for an
+ *						   IIO device
+ * @dev: Device for devm ownership
+ * @indio_dev: IIO device to which to attach this buffer.
+ * @chan: DMA channel
+ * @dir: Direction of buffer (in or out)
+ *
+ * This allocates a new IIO buffer with devm_iio_dmaengine_buffer_alloc()
+ * and attaches it to an IIO device with iio_device_attach_buffer().
+ * It also appends the INDIO_BUFFER_HARDWARE mode to the supported modes of the
+ * IIO device.
+ *
+ * This is the same as devm_iio_dmaengine_buffer_setup_ext() except that the
+ * caller manages requesting and releasing the DMA channel handle.
+ */
+int devm_iio_dmaengine_buffer_setup_with_handle(struct device *dev,
+						struct iio_dev *indio_dev,
+						struct dma_chan *chan,
+						enum iio_buffer_direction dir)
+{
+	struct iio_buffer *buffer;
+
+	buffer = __iio_dmaengine_buffer_setup_ext(indio_dev, chan, dir);
+	if (IS_ERR(buffer))
+		return PTR_ERR(buffer);
+
+	return devm_add_action_or_reset(dev, devm_iio_dmaengine_buffer_free,
+					buffer);
+}
+EXPORT_SYMBOL_NS_GPL(devm_iio_dmaengine_buffer_setup_with_handle,
+		     "IIO_DMAENGINE_BUFFER");
+
 MODULE_AUTHOR("Lars-Peter Clausen <[e-mail]>");
 MODULE_DESCRIPTION("DMA buffer for the IIO framework");
 MODULE_LICENSE("GPL");

include/linux/iio/buffer-dmaengine.h

···
 
 struct iio_dev;
 struct device;
+struct dma_chan;
 
 void iio_dmaengine_buffer_teardown(struct iio_buffer *buffer);
 struct iio_buffer *iio_dmaengine_buffer_setup_ext(struct device *dev,
···
 					struct iio_dev *indio_dev,
 					const char *channel,
 					enum iio_buffer_direction dir);
+int devm_iio_dmaengine_buffer_setup_with_handle(struct device *dev,
+						struct iio_dev *indio_dev,
+						struct dma_chan *chan,
+						enum iio_buffer_direction dir);
 
 #define devm_iio_dmaengine_buffer_setup(dev, indio_dev, channel)	\
 	devm_iio_dmaengine_buffer_setup_ext(dev, indio_dev, channel,	\