Re: [PATCH] dmaengine: lpc18xx-dmamux: simplify allocation

[Vladimir Zapolskiy <vz@mleia.com>]

On 4/7/26 06:51, Rosen Penev wrote:
> Use a flexible array member to combine allocations. Requires
> preparation, aka reshuffling before the actual allocation to get the
> proper size.
> 
> Add __counted_by for extra runtime analysis.
> 
> Signed-off-by: Rosen Penev <rosenp@gmail.com>
> ---
>   drivers/dma/lpc18xx-dmamux.c | 42 +++++++++++++++++-------------------
>   1 file changed, 20 insertions(+), 22 deletions(-)
> 
> diff --git a/drivers/dma/lpc18xx-dmamux.c b/drivers/dma/lpc18xx-dmamux.c
> index d3ff521951b8..5dfefbc496da 100644
> --- a/drivers/dma/lpc18xx-dmamux.c
> +++ b/drivers/dma/lpc18xx-dmamux.c
> @@ -32,11 +32,11 @@ struct lpc18xx_dmamux {
>   
>   struct lpc18xx_dmamux_data {
>   	struct dma_router dmarouter;
> -	struct lpc18xx_dmamux *muxes;
>   	u32 dma_master_requests;
>   	u32 dma_mux_requests;
>   	struct regmap *reg;
>   	spinlock_t lock;
> +	struct lpc18xx_dmamux muxes[] __counted_by(dma_master_requests);
>   };
>   
>   static void lpc18xx_dmamux_free(struct device *dev, void *route_data)
> @@ -122,12 +122,30 @@ static int lpc18xx_dmamux_probe(struct platform_device *pdev)
>   {
>   	struct device_node *dma_np, *np = pdev->dev.of_node;
>   	struct lpc18xx_dmamux_data *dmamux;
> +	u32 dma_master_requests;
>   	int ret;
>   
> -	dmamux = devm_kzalloc(&pdev->dev, sizeof(*dmamux), GFP_KERNEL);
> +	dma_np = of_parse_phandle(np, "dma-masters", 0);
> +	if (!dma_np) {
> +		dev_err(&pdev->dev, "can't get dma master\n");
> +		return -ENODEV;
> +	}
> +
> +	ret = of_property_read_u32(dma_np, "dma-requests",
> +				   &dma_master_requests);
> +	of_node_put(dma_np);
> +	if (ret) {
> +		dev_err(&pdev->dev, "missing master dma-requests property\n");
> +		return ret;
> +	}
> +
> +	dmamux = devm_kzalloc(&pdev->dev, struct_size(dmamux, muxes, dma_master_requests),
> +			GFP_KERNEL);
>   	if (!dmamux)
>   		return -ENOMEM;
>   
> +	dmamux->dma_master_requests = dma_master_requests;
> +
>   	dmamux->reg = syscon_regmap_lookup_by_compatible("nxp,lpc1850-creg");
>   	if (IS_ERR(dmamux->reg)) {
>   		dev_err(&pdev->dev, "syscon lookup failed\n");
> @@ -141,26 +159,6 @@ static int lpc18xx_dmamux_probe(struct platform_device *pdev)
>   		return ret;
>   	}
>   
> -	dma_np = of_parse_phandle(np, "dma-masters", 0);
> -	if (!dma_np) {
> -		dev_err(&pdev->dev, "can't get dma master\n");
> -		return -ENODEV;
> -	}
> -
> -	ret = of_property_read_u32(dma_np, "dma-requests",
> -				   &dmamux->dma_master_requests);
> -	of_node_put(dma_np);
> -	if (ret) {
> -		dev_err(&pdev->dev, "missing master dma-requests property\n");
> -		return ret;
> -	}
> -
> -	dmamux->muxes = devm_kcalloc(&pdev->dev, dmamux->dma_master_requests,
> -				     sizeof(struct lpc18xx_dmamux),
> -				     GFP_KERNEL);
> -	if (!dmamux->muxes)
> -		return -ENOMEM;
> -
>   	spin_lock_init(&dmamux->lock);
>   	platform_set_drvdata(pdev, dmamux);
>   	dmamux->dmarouter.dev = &pdev->dev;

Reviewed-by: Vladimir Zapolskiy <vz@mleia.com>

-- 
Best wishes,
Vladimir