iio: buffer-dma: support getting the DMA channel

Implement the .get_dma_dev() callback for DMA buffers by returning the
device that owns the DMA channel. This allows the core DMABUF
infrastructure to properly map DMA buffers using the correct device,
avoiding the need for bounce buffers on systems where memory is mapped
above the 32-bit range.

The function returns the DMA queue's device, which is the actual device
responsible for DMA operations in buffer-dma implementations.

Cc: stable@vger.kernel.org
Reviewed-by: David Lechner <dlechner@baylibre.com>
Signed-off-by: Nuno Sá <nuno.sa@analog.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

1 files changed, 6 insertions, 0 deletions

diff --git a/drivers/iio/buffer/industrialio-buffer-dma.c b/drivers/iio/buffer/industrialio-buffer-dma.c
index ee294a775e8a..7a7a9d37339b 100644
--- a/drivers/iio/buffer/industrialio-buffer-dma.c
+++ b/drivers/iio/buffer/industrialio-buffer-dma.c
@@ -786,6 +786,12 @@ out_end_signalling:
 }
 EXPORT_SYMBOL_NS_GPL(iio_dma_buffer_enqueue_dmabuf, "IIO_DMA_BUFFER");
 
+struct device *iio_dma_buffer_get_dma_dev(struct iio_buffer *buffer)
+{
+	return iio_buffer_to_queue(buffer)->dev;
+}
+EXPORT_SYMBOL_NS_GPL(iio_dma_buffer_get_dma_dev, "IIO_DMA_BUFFER");
+
 void iio_dma_buffer_lock_queue(struct iio_buffer *buffer)
 {
 	struct iio_dma_buffer_queue *queue = iio_buffer_to_queue(buffer);