iio: buffer-dmaengine: Support new DMABUF based userspace API

Use the functions provided by the buffer-dma core to implement the
DMABUF userspace API in the buffer-dmaengine IIO buffer implementation.

Since we want to be able to transfer an arbitrary number of bytes and
not necesarily the full DMABUF, the associated scatterlist is converted
to an array of DMA addresses + lengths, which is then passed to
dmaengine_prep_slave_dma_array().

Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Co-developed-by: Nuno Sa <nuno.sa@analog.com>
Signed-off-by: Nuno Sa <nuno.sa@analog.com>
Link: https://patch.msgid.link/20240620122726.41232-6-paul@crapouillou.net
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

Author: pcercuei

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

@@ -65,13 +65,21 @@ static void iio_dmaengine_buffer_block_done(void *data,
 int iio_dmaengine_buffer_submit_block(struct iio_dma_buffer_queue *queue,
 	struct iio_dma_buffer_block *block)
 {
-	struct dmaengine_buffer *dmaengine_buffer;
+	struct dmaengine_buffer *dmaengine_buffer =
+		iio_buffer_to_dmaengine_buffer(&block->queue->buffer);
 	struct dma_async_tx_descriptor *desc;
 	enum dma_transfer_direction dma_dir;
+#ifndef CONFIG_IIO_DMA_BUF_MMAP_LEGACY
+	struct scatterlist *sgl;
+	struct dma_vec *vecs;
+#endif
 	size_t max_size;
 	dma_cookie_t cookie;
-
-	dmaengine_buffer = iio_buffer_to_dmaengine_buffer(&block->queue->buffer);
+#ifndef CONFIG_IIO_DMA_BUF_MMAP_LEGACY
+	size_t len_total;
+	unsigned int i;
+	int nents;
+#endif
 
 #ifdef CONFIG_IIO_DMA_BUF_MMAP_LEGACY
 	if (queue->buffer.direction == IIO_BUFFER_DIRECTION_IN) {
@@ -101,20 +109,15 @@ int iio_dmaengine_buffer_submit_block(struct iio_dma_buffer_queue *queue,
 			DMA_PREP_INTERRUPT);
 		if (!desc)
 			return -ENOMEM;
-
-		desc->callback_result = iio_dmaengine_buffer_block_done;
-		desc->callback_param = block;
 	}
 #else
 	max_size = min(block->size, dmaengine_buffer->max_size);
 	max_size = round_down(max_size, dmaengine_buffer->align);
 
-	if (queue->buffer.direction == IIO_BUFFER_DIRECTION_IN) {
-		block->bytes_used = max_size;
+	if (queue->buffer.direction == IIO_BUFFER_DIRECTION_IN)
 		dma_dir = DMA_DEV_TO_MEM;
-	} else {
+	else
 		dma_dir = DMA_MEM_TO_DEV;
-	}
 
 	if (block->sg_table) {
 		sgl = block->sg_table->sgl;
@@ -145,23 +148,25 @@ int iio_dmaengine_buffer_submit_block(struct iio_dma_buffer_queue *queue,
 							 vecs, nents, dma_dir,
 							 DMA_PREP_INTERRUPT);
 		kfree(vecs);
->>>>>>> 7232b3a0f5ea (s)
 	} else {
-		dma_dir = DMA_MEM_TO_DEV;
-	}
+		if (queue->buffer.direction == IIO_BUFFER_DIRECTION_IN)
+			block->bytes_used = max_size;
 
-	if (!block->bytes_used || block->bytes_used > max_size)
-		return -EINVAL;
+		if (!block->bytes_used || block->bytes_used > max_size)
+			return -EINVAL;
 
-	desc = dmaengine_prep_slave_single(dmaengine_buffer->chan,
-		block->phys_addr, block->bytes_used, dma_dir,
-		DMA_PREP_INTERRUPT);
+		desc = dmaengine_prep_slave_single(dmaengine_buffer->chan,
+						   block->phys_addr,
+						   block->bytes_used,
+						   dma_dir,
+						   DMA_PREP_INTERRUPT);
+	}
 	if (!desc)
 		return -ENOMEM;
-
+#endif
 	desc->callback_result = iio_dmaengine_buffer_block_done;
 	desc->callback_param = block;
-#endif
+
 	cookie = dmaengine_submit(desc);
 	if (dma_submit_error(cookie))
 		return dma_submit_error(cookie);
@@ -213,6 +218,13 @@ static const struct iio_buffer_access_funcs iio_dmaengine_buffer_ops = {
 	.enqueue_block = iio_dma_buffer_enqueue_block,
 	.dequeue_block = iio_dma_buffer_dequeue_block,
 	.mmap = iio_dma_buffer_mmap,
+#else
+	.enqueue_dmabuf = iio_dma_buffer_enqueue_dmabuf,
+	.attach_dmabuf = iio_dma_buffer_attach_dmabuf,
+	.detach_dmabuf = iio_dma_buffer_detach_dmabuf,
+
+	.lock_queue = iio_dma_buffer_lock_queue,
+	.unlock_queue = iio_dma_buffer_unlock_queue,
 #endif
 	.modes = INDIO_BUFFER_HARDWARE,
 	.flags = INDIO_BUFFER_FLAG_FIXED_WATERMARK,