Hi Jonathan,
Le jeudi 21 décembre 2023 à 16:12 +0000, Jonathan Cameron a écrit :
On Tue, 19 Dec 2023 18:50:08 +0100 Paul Cercueil paul@crapouillou.net wrote:
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
One question inline. Otherwise looks fine to me.
J
v3: Use the new dmaengine_prep_slave_dma_array(), and adapt the code to work with the new functions introduced in industrialio-buffer- dma.c.
v5: - Use the new dmaengine_prep_slave_dma_vec(). - Restrict to input buffers, since output buffers are not yet supported by IIO buffers.
.../buffer/industrialio-buffer-dmaengine.c | 52 ++++++++++++++++--- 1 file changed, 46 insertions(+), 6 deletions(-)
diff --git a/drivers/iio/buffer/industrialio-buffer-dmaengine.c b/drivers/iio/buffer/industrialio-buffer-dmaengine.c index 5f85ba38e6f6..825d76a24a67 100644 --- a/drivers/iio/buffer/industrialio-buffer-dmaengine.c +++ b/drivers/iio/buffer/industrialio-buffer-dmaengine.c @@ -64,15 +64,51 @@ static int iio_dmaengine_buffer_submit_block(struct iio_dma_buffer_queue *queue, struct dmaengine_buffer *dmaengine_buffer = iio_buffer_to_dmaengine_buffer(&queue->buffer); struct dma_async_tx_descriptor *desc;
- unsigned int i, nents;
- struct scatterlist *sgl;
- struct dma_vec *vecs;
- size_t max_size;
dma_cookie_t cookie;
- size_t len_total;
- block->bytes_used = min(block->size, dmaengine_buffer-
max_size);
- block->bytes_used = round_down(block->bytes_used,
dmaengine_buffer->align);
- if (queue->buffer.direction != IIO_BUFFER_DIRECTION_IN) {
/* We do not yet support output buffers. */return -EINVAL;- }
- desc = dmaengine_prep_slave_single(dmaengine_buffer->chan,
block->phys_addr, block->bytes_used,DMA_DEV_TO_MEM,
DMA_PREP_INTERRUPT);
- if (block->sg_table) {
sgl = block->sg_table->sgl;nents = sg_nents_for_len(sgl, block->bytes_used);Are we guaranteed the length in the sglist is enough? If not this can return an error code.
The length of the sglist will always be enough, the iio_buffer_enqueue_dmabuf() function already checks that block-
bytes_used is equal or smaller than the size of the DMABUF.
It is quite a few functions above in the call stack though, so I can handle the errors of sg_nents_for_len() here if you think makes sense.
Cheers, -Paul
vecs = kmalloc_array(nents, sizeof(*vecs),GFP_KERNEL);
if (!vecs)return -ENOMEM;len_total = block->bytes_used;for (i = 0; i < nents; i++) {vecs[i].addr = sg_dma_address(sgl);vecs[i].len = min(sg_dma_len(sgl),len_total);
len_total -= vecs[i].len;sgl = sg_next(sgl);}desc =dmaengine_prep_slave_dma_vec(dmaengine_buffer->chan,
vecs, nents,DMA_DEV_TO_MEM,
DMA_PREP_INTERRUPT);
kfree(vecs);- } else {
max_size = min(block->size, dmaengine_buffer-max_size);
max_size = round_down(max_size, dmaengine_buffer-align);
block->bytes_used = max_size;desc =dmaengine_prep_slave_single(dmaengine_buffer->chan,
block-phys_addr,
block-bytes_used,
DMA_DEV_TO_MEM,DMA_PREP_INTERRUPT);
- }
if (!desc) return -ENOMEM;