linux-kernel - Re: [PATCH v3 3/8] dma-mapping: add dma_{map,unmap}

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Date:	Wed, 10 Feb 2016 10:25:07 +0000
From:	Robin Murphy <robin.murphy@....com>
To:	Niklas Söderlund 
	<niklas.soderlund+renesas@...natech.se>,
	linux-renesas-soc@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	dmaengine@...r.kernel.org, iommu@...ts.linux-foundation.org
Cc:	linux-arch@...r.kernel.org, arnd@...db.de, geert+renesas@...der.be,
	vinod.koul@...el.com, linus.walleij@...aro.org,
	laurent.pinchart@...asonboard.com, dan.j.williams@...el.com
Subject: Re: [PATCH v3 3/8] dma-mapping: add dma_{map,unmap}_resource

Hi Niklas,

Thanks for doing this, it looks good. Just a couple of minor comments on 
this and the next patch...

On 10/02/16 00:57, Niklas Söderlund wrote:
> Map/Unmap a device resource from a physical address. If no dma_map_ops
> method is available the operation is a no-op.
>
> Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@...natech.se>
> ---
>   include/linux/dma-mapping.h | 27 +++++++++++++++++++++++++++
>   1 file changed, 27 insertions(+)
>
> diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
> index e3aba4e..21bf986 100644
> --- a/include/linux/dma-mapping.h
> +++ b/include/linux/dma-mapping.h
> @@ -216,6 +216,33 @@ static inline void dma_unmap_page(struct device *dev, dma_addr_t addr,
>   	debug_dma_unmap_page(dev, addr, size, dir, false);
>   }
>
> +static inline dma_addr_t dma_map_resource(struct device *dev,
> +					  phys_addr_t phys_addr,
> +					  size_t size,
> +					  enum dma_data_direction dir,
> +					  struct dma_attrs *attrs)
> +{
> +	struct dma_map_ops *ops = get_dma_ops(dev);
> +
> +	BUG_ON(!valid_dma_direction(dir));

I think it would be worth also having the same inverse pfn_valid() check 
as ioremap() here, to make sure this is similarly hard to misuse.

Robin.

> +	if (ops->map_resource)
> +		return ops->map_resource(dev, phys_addr, size, dir, attrs);
> +
> +	return phys_addr;
> +}
> +
> +static inline void dma_unmap_resource(struct device *dev, dma_addr_t addr,
> +				      size_t size, enum dma_data_direction dir,
> +				      struct dma_attrs *attrs)
> +{
> +	struct dma_map_ops *ops = get_dma_ops(dev);
> +
> +	BUG_ON(!valid_dma_direction(dir));
> +	if (ops->unmap_resource)
> +		ops->unmap_resource(dev, addr, size, dir, attrs);
> +
> +}
> +
>   static inline void dma_sync_single_for_cpu(struct device *dev, dma_addr_t addr,
>   					   size_t size,
>   					   enum dma_data_direction dir)
>