[PATCH v2] dmaengine: xilinx: xdma: use kzalloc_flex()

[Frank Li]

On Mon, Oct 05, 2026 at 12:26:21PM -0700, Rosen Penev wrote:
> Change desc_blocks to a flexible array member so the descriptor and
> its block array are allocated together, removing one allocation and
> its error handling.
>
> Add __counted_by for extra runtime analysis, and set dblk_num right
> after allocation which is already done by kzalloc_flex() for GCC >= 15.
>
> Assisted-by: LLM
> Signed-off-by: Rosen Penev <rosenp at gmail.com>
> ---

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

>  drivers/dma/xilinx/xdma.c | 15 +++++----------
>  1 file changed, 5 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/dma/xilinx/xdma.c b/drivers/dma/xilinx/xdma.c
> index 8d4a5d14e8db..16d202722245 100644
> --- a/drivers/dma/xilinx/xdma.c
> +++ b/drivers/dma/xilinx/xdma.c
> @@ -81,7 +81,6 @@ struct xdma_chan {
>   * @vdesc: Virtual DMA descriptor
>   * @chan: DMA channel pointer
>   * @dir: Transferring direction of the request
> - * @desc_blocks: Hardware descriptor blocks
>   * @dblk_num: Number of hardware descriptor blocks
>   * @desc_num: Number of hardware descriptors
>   * @completed_desc_num: Completed hardware descriptors
> @@ -91,12 +90,12 @@ struct xdma_chan {
>   * @period_size: Size of a period in bytes in cyclic transfers
>   * @frames_left: Number of frames left in interleaved DMA transfer
>   * @error: tx error flag
> + * @desc_blocks: Hardware descriptor blocks
>   */
>  struct xdma_desc {
>  	struct virt_dma_desc		vdesc;
>  	struct xdma_chan		*chan;
>  	enum dma_transfer_direction	dir;
> -	struct xdma_desc_block		*desc_blocks;
>  	u32				dblk_num;
>  	u32				desc_num;
>  	u32				completed_desc_num;
> @@ -106,6 +105,7 @@ struct xdma_desc {
>  	u32				period_size;
>  	u32				frames_left;
>  	bool				error;
> +	struct xdma_desc_block		desc_blocks[] __counted_by(dblk_num);
>  };
>
>  #define XDMA_DEV_STATUS_REG_DMA		BIT(0)
> @@ -255,7 +255,6 @@ static void xdma_free_desc(struct virt_dma_desc *vdesc)
>  			      sw_desc->desc_blocks[i].virt_addr,
>  			      sw_desc->desc_blocks[i].dma_addr);
>  	}
> -	kfree(sw_desc->desc_blocks);
>  	kfree(sw_desc);
>  }
>
> @@ -276,26 +275,22 @@ xdma_alloc_desc(struct xdma_chan *chan, u32 desc_num, bool cyclic)
>  	void *addr;
>  	int i, j;
>
> -	sw_desc = kzalloc_obj(*sw_desc, GFP_NOWAIT);
> +	dblk_num = DIV_ROUND_UP(desc_num, XDMA_DESC_ADJACENT);
> +	sw_desc = kzalloc_flex(*sw_desc, desc_blocks, dblk_num, GFP_NOWAIT);
>  	if (!sw_desc)
>  		return NULL;
>
> +	sw_desc->dblk_num = dblk_num;
>  	sw_desc->chan = chan;
>  	sw_desc->desc_num = desc_num;
>  	sw_desc->cyclic = cyclic;
>  	sw_desc->error = false;
> -	dblk_num = DIV_ROUND_UP(desc_num, XDMA_DESC_ADJACENT);
> -	sw_desc->desc_blocks = kzalloc_objs(*sw_desc->desc_blocks, dblk_num,
> -					    GFP_NOWAIT);
> -	if (!sw_desc->desc_blocks)
> -		goto failed;
>
>  	if (cyclic)
>  		control = XDMA_DESC_CONTROL_CYCLIC;
>  	else
>  		control = XDMA_DESC_CONTROL(1, 0);
>
> -	sw_desc->dblk_num = dblk_num;
>  	for (i = 0; i < sw_desc->dblk_num; i++) {
>  		addr = dma_pool_alloc(chan->desc_pool, GFP_NOWAIT, &dma_addr);
>  		if (!addr)
> --
> 2.56.0
>