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Subject: Re: [PATCH 1/5 v2] dma-mapping: add generic dma_get_page_shift API
From: Michael Ellerman <mpe@ellerman.id.au>
To: Nishanth Aravamudan <nacc@linux.vnet.ibm.com>
Cc: Matthew Wilcox <willy@linux.intel.com>, Keith Busch
 <keith.busch@intel.com>,  Benjamin Herrenschmidt
 <benh@kernel.crashing.org>, Paul Mackerras <paulus@samba.org>, Alexey
 Kardashevskiy <aik@ozlabs.ru>,  David Gibson <david@gibson.dropbear.id.au>,
 Christoph Hellwig <hch@infradead.org>,  linux-nvme@lists.infradead.org,
 linux-kernel@vger.kernel.org,  linuxppc-dev@lists.ozlabs.org, Arnd Bergmann
 <arnd@arndb.de>
Date: Tue, 06 Oct 2015 14:43:36 +1100
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 <20151002200953.GB40695@linux.vnet.ibm.com>
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On Fri, 2015-10-02 at 13:11 -0700, Nishanth Aravamudan wrote:
> Drivers like NVMe need to be able to determine the page size used for
> DMA transfers. Add a new API that defaults to return PAGE_SHIFT on all
> architectures.
> 
> Signed-off-by: Nishanth Aravamudan <nacc@linux.vnet.ibm.com>
> 
> diff --git a/include/asm-generic/dma-mapping-common.h b/include/asm-generic/dma-mapping-common.h
> index b1bc954..86e4e97 100644
> --- a/include/asm-generic/dma-mapping-common.h
> +++ b/include/asm-generic/dma-mapping-common.h
> @@ -355,4 +355,11 @@ static inline int dma_set_mask(struct device *dev, u64 mask)
>  }
>  #endif
>  
> +#ifndef HAVE_ARCH_DMA_GET_PAGE_SHIFT
> +static inline unsigned long dma_get_page_shift(struct device *dev)
> +{
> +	return PAGE_SHIFT;
> +}
> +#endif
> +
>  #endif
> 

Adding Arnd who is asm-generic maintainer.

Arnd/Christoph can one of you give us an ack for this patch?

cheers