[PATCH V2 7/8] dmaengine: zynqmp_dma: Reject zero-length memcpy transfers

[Frank Li]

On Fri, Aug 14, 2026 at 10:26:15AM +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>
> ---

Reviewed-by: Frank Li <Frank.Li at nxp.com>

> Changes in V2:
> - No change
> ---
>  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 194abfd6cb25..921d3d9f6ed6 100644
> --- a/drivers/dma/xilinx/zynqmp_dma.c
> +++ b/drivers/dma/xilinx/zynqmp_dma.c
> @@ -837,7 +837,8 @@ 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,
> @@ -852,6 +853,9 @@ 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);
> --
> 2.44.4
>