linux-kernel - Re: [PATCH] Platform: goldfish: goldfish_pipe.c: Add DMA support using managed version

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Date:	Fri, 12 Feb 2016 02:17:40 -0800
From:	Joe Perches <joe@...ches.com>
To:	Shraddha Barke <shraddha.6596@...il.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Peter Senna Tschudin <peter.senna@...il.com>,
	Dan Carpenter <dan.carpenter@...cle.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Platform: goldfish: goldfish_pipe.c: Add DMA support
 using managed version

On Fri, 2016-02-12 at 12:53 +0530, Shraddha Barke wrote:
> setup_access_params_addr has 2 goals-
> 
> -Initialize the access_params field so that it can be used to send and read
> commands from the device in access_with_param
> -Get a bus address for the allocated memory to transfer to the device.
> 
> Replace the combination of devm_kzalloc and _pa() with dmam_alloc_coherent.

trivia:

> diff --git a/drivers/platform/goldfish/goldfish_pipe.c b/drivers/platform/goldfish/goldfish_pipe.c
[]
> @@ -217,17 +218,18 @@ static int valid_batchbuffer_addr(struct goldfish_pipe_dev *dev,
>  static int setup_access_params_addr(struct platform_device *pdev,
>  					struct goldfish_pipe_dev *dev)
>  {
> -	u64 paddr;
> +	dma_addr_t dma_handle;
>  	struct access_params *aps;
>  
> -	aps = devm_kzalloc(&pdev->dev, sizeof(struct access_params), GFP_KERNEL);
> -	if (!aps)
> -		return -1;
> +	aps = dmam_alloc_coherent(&pdev->dev, sizeof(struct access_params),
> +				    &dma_handle, GFP_KERNEL);
> +	if (!aps) {
> +		dev_err(&pdev->dev, "allocate buffer failed\n");

This is still an unnecessary allocation failure message.
There's already a generic OOM message and stack dump emitted.