Re: [PATCH] net: dma: use dmaengine_desc_set_callback()

[Joe Damato <joe@dama.to>]

On Mon, Nov 02, 2026 at 02:19:16PM -0500, Frank.Li@oss.nxp.com wrote:
> From: Frank Li <Frank.Li@nxp.com>
> 
> Replace open-coded assignments to callback and callback_param fields
> of struct dma_async_tx_descriptor with calls to the
> dmaengine_desc_set_callback() helper across net drivers.
> 
> No functional change intended. Prepare to make struct
> dma_async_tx_descriptor private to the DMA engine.
> 
> Signed-off-by: Frank Li <Frank.Li@nxp.com>
> ---
>  drivers/net/ethernet/allwinner/sun4i-emac.c       |  3 +--
>  drivers/net/ethernet/micrel/ks8842.c              |  6 ++----
>  drivers/net/ethernet/xilinx/xilinx_axienet_main.c |  6 ++----
>  drivers/net/wwan/qcom_bam_dmux.c                  | 10 ++++------
>  4 files changed, 9 insertions(+), 16 deletions(-)

[...]

> diff --git a/drivers/net/wwan/qcom_bam_dmux.c b/drivers/net/wwan/qcom_bam_dmux.c
> index cc6ace8d64371..1479f8362e04e 100644
> --- a/drivers/net/wwan/qcom_bam_dmux.c
> +++ b/drivers/net/wwan/qcom_bam_dmux.c
> @@ -195,9 +195,8 @@ static bool bam_dmux_skb_dma_submit_tx(struct bam_dmux_skb_dma *skb_dma)
>  		return false;
>  	}
>  
> -	desc->callback = bam_dmux_tx_callback;
> -	desc->callback_param = skb_dma;
> -	desc->cookie = dmaengine_submit(desc);
> +	dmaengine_desc_set_callback(desc, bam_dmux_tx_callback, NULL, skb_dma);
> +	dmaengine_submit(desc);
>  	return true;
>  }
>  
> @@ -477,9 +476,8 @@ static bool bam_dmux_skb_dma_submit_rx(struct bam_dmux_skb_dma *skb_dma)
>  		return false;
>  	}
>  
> -	desc->callback = bam_dmux_rx_callback;
> -	desc->callback_param = skb_dma;
> -	desc->cookie = dmaengine_submit(desc);
> +	dmaengine_desc_set_callback(desc, bam_dmux_rx_callback, NULL, skb_dma);
> +	dmaengine_submit(desc);

I noticed in the above that the return value of dmaengine_submit is discarded
instead of stored.

Is that intentional? I suppose it might be because AFAICT cookie is never
used and the commit message says "no functional change intended".

Reviewed-by: Joe Damato <joe@dama.to>