[PATCH 5/6] dmaengine: zynqmp_dma: Reject zero-length memcpy transfers

[Frank Li]

On Thu, Aug 06, 2026 at 06:00:13PM +0530, Golla Nagendra wrote:
> Zero-length prep_memcpy() needlessly consumed a descriptor slot. Reject
> zero-length memcpy at prep time and document the behaviour.
>
> Signed-off-by: Golla Nagendra <nagendra.golla at amd.com>
> ---

Is it caller problem, which pass down zero len? or are there special usage,
such as memory barrier.

Frank

>  drivers/dma/xilinx/zynqmp_dma.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/dma/xilinx/zynqmp_dma.c b/drivers/dma/xilinx/zynqmp_dma.c
> index 2d56ea08ce45..e70874d65123 100644
> --- a/drivers/dma/xilinx/zynqmp_dma.c
> +++ b/drivers/dma/xilinx/zynqmp_dma.c
> @@ -836,7 +836,8 @@ static void zynqmp_dma_synchronize(struct dma_chan *dchan)
>   * @len: Transfer length
>   * @flags: transfer ack flags
>   *
> - * Return: Async transaction descriptor on success and NULL on failure
> + * Return: Async transaction descriptor on success and NULL on failure or
> + *	   zero length transfer
>   */
>  static struct dma_async_tx_descriptor *zynqmp_dma_prep_memcpy(
>  				struct dma_chan *dchan, dma_addr_t dma_dst,
> @@ -851,6 +852,9 @@ static struct dma_async_tx_descriptor *zynqmp_dma_prep_memcpy(
>
>  	chan = to_chan(dchan);
>
> +	if (!len)
> +		return NULL;
> +
>  	desc_cnt = DIV_ROUND_UP(len, ZYNQMP_DMA_MAX_TRANS_LEN);
>
>  	spin_lock_irqsave(&chan->lock, irqflags);
> --
> 2.43.7
>