linux-kernel - Re: [PATCH 2/5] dma-mapping: Add devm_ interface for dma_map

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Message-ID: <20140516210805.GO5379@htj.dyndns.org>
Date:	Fri, 16 May 2014 17:08:05 -0400
From:	Tejun Heo <tj@...nel.org>
To:	Eli Billauer <eli.billauer@...il.com>
Cc:	gregkh@...uxfoundation.org, devel@...verdev.osuosl.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/5] dma-mapping: Add devm_ interface for dma_map_single()

Hello,

On Fri, May 16, 2014 at 11:26:36AM +0300, Eli Billauer wrote:
> +dma_addr_t dmam_map_single(struct device *dev, void *ptr, size_t size,
> +			   enum dma_data_direction direction)
> +
> +{
> +	struct dma_devres *dr;
> +	dma_addr_t dma_handle;
> +
> +	dr = devres_alloc(dmam_map_single_release, sizeof(*dr), GFP_KERNEL);
> +	if (!dr)
> +		return 0;
> +
> +	dma_handle = dma_map_single(dev, ptr, size, direction);

Don't we wanna map the underlying operation - dma_map_single_attrs() -
instead?

> +	if (dma_mapping_error(dev, dma_handle)) {
> +		devres_free(dr);
> +		return 0;

Can't we just keep returning dma_handle?  Even if that means invoking
->mapping_error() twice?  It's yucky to have subtly different error
return especially because in most cases it won't fail.

Thanks.

-- 
tejun
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