Re: [PATCH v3 09/11] iio: buffer-dma: Enable support for DMABUFs

[Jonathan Cameron <jic23@kernel.org>]

On Mon,  3 Apr 2023 17:47:58 +0200
Paul Cercueil <paul@crapouillou.net> wrote:

> Implement iio_dma_buffer_attach_dmabuf(), iio_dma_buffer_detach_dmabuf()
> and iio_dma_buffer_transfer_dmabuf(), which can then be used by the IIO
> DMA buffer implementations.
> 
> Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Hi Paul,

A few superficially comments.

Jonathan

> 
> ---
> v3: Update code to provide the functions that will be used as callbacks
> for the new IOCTLs.
> ---
>  drivers/iio/buffer/industrialio-buffer-dma.c | 157 +++++++++++++++++--
>  include/linux/iio/buffer-dma.h               |  24 +++
>  2 files changed, 168 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/iio/buffer/industrialio-buffer-dma.c b/drivers/iio/buffer/industrialio-buffer-dma.c
> index e14814e0d4c8..422bd784fd1e 100644
> --- a/drivers/iio/buffer/industrialio-buffer-dma.c
> +++ b/drivers/iio/buffer/industrialio-buffer-dma.c
...

> @@ -412,8 +448,12 @@ static void iio_dma_buffer_submit_block(struct iio_dma_buffer_queue *queue,
>  
>  	block->state = IIO_BLOCK_STATE_ACTIVE;
>  	iio_buffer_block_get(block);
> +

Trivial, but I'd rather not see unrelated white space changes in a patch
doing anything else.

>  	ret = queue->ops->submit(queue, block);
>  	if (ret) {
> +		if (!block->fileio)
> +			iio_buffer_signal_dmabuf_done(block->attach, ret);
> +
>  		/*
>  		 * This is a bit of a problem and there is not much we can do
>  		 * other then wait for the buffer to be disabled and re-enabled
> @@ -645,6 +685,97 @@ size_t iio_dma_buffer_data_available(struct iio_buffer *buf)
>  }
>  EXPORT_SYMBOL_GPL(iio_dma_buffer_data_available);

...

> +int iio_dma_buffer_enqueue_dmabuf(struct iio_buffer *buffer,
> +				  struct iio_dma_buffer_block *block,
> +				  struct sg_table *sgt,
> +				  size_t size, bool cyclic)
> +{
> +	struct iio_dma_buffer_queue *queue = iio_buffer_to_queue(buffer);
> +	int ret = 0;

No need to init.

> +
> +	mutex_lock(&queue->lock);
> +	ret = iio_dma_can_enqueue_block(block);
> +	if (ret < 0)
> +		goto out_mutex_unlock;
> +
> +	block->bytes_used = size;
> +	block->cyclic = cyclic;
> +	block->sg_table = sgt;
> +
> +	iio_dma_buffer_enqueue(queue, block);
> +
> +out_mutex_unlock:
> +	mutex_unlock(&queue->lock);
> +	return ret;
> +}
> +EXPORT_SYMBOL_GPL(iio_dma_buffer_enqueue_dmabuf);

Obviously an unrelated activity but good to namespace these
in a future patch set.

> +
>  /**
>   * iio_dma_buffer_set_bytes_per_datum() - DMA buffer set_bytes_per_datum callback
>   * @buffer: Buffer to set the bytes-per-datum for
> diff --git a/include/linux/iio/buffer-dma.h b/include/linux/iio/buffer-dma.h
> index 490b93f76fa8..e5e5817e99db 100644
> --- a/include/linux/iio/buffer-dma.h
> +++ b/include/linux/iio/buffer-dma.h

>  /**
>   * enum iio_block_state - State of a struct iio_dma_buffer_block
> @@ -41,6 +43,7 @@ enum iio_block_state {
>   * @queue: Parent DMA buffer queue
>   * @kref: kref used to manage the lifetime of block
>   * @state: Current state of the block
> + * @fileio: True if this buffer is used for fileio mode

Docs need update for the other two new elements.

>   */
>  struct iio_dma_buffer_block {
>  	/* May only be accessed by the owner of the block */
> @@ -63,6 +66,11 @@ struct iio_dma_buffer_block {
>  	 * queue->list_lock if the block is not owned by the core.
>  	 */
>  	enum iio_block_state state;
> +
> +	bool fileio;
> +
> +	struct dma_buf_attachment *attach;
> +	struct sg_table *sg_table;
>  };