linux-kernel - Re: [PATCH 2/4] dma-mapping: add get_required

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Message-Id: <20110629171304B.fujita.tomonori@lab.ntt.co.jp>
Date:	Wed, 29 Jun 2011 17:19:50 +0900
From:	FUJITA Tomonori <fujita.tomonori@....ntt.co.jp>
To:	nacc@...ibm.com
Cc:	miltonm@....com, linuxppc-dev@...ts.ozlabs.org,
	linux-kernel@...r.kernel.org, benh@...nel.crashing.org,
	vinod.koul@...el.com, dan.j.williams@...el.com
Subject: Re: [PATCH 2/4] dma-mapping: add get_required_mask if arch
 overrides default

On Fri, 24 Jun 2011 12:05:23 -0700
Nishanth Aravamudan <nacc@...ibm.com> wrote:

> From: Milton Miller <miltonm@....com>
> 
> If an architecture sets ARCH_HAS_DMA_GET_REQUIRED_MASK and has settable
> dma_map_ops, the required mask may change by the ops implementation.
> For example, a system that always has an mmu inline may only require 32
> bits while a swiotlb would desire bits to cover all of memory.
> 
> Therefore add the field if the architecture does not use the generic
> definition of dma_get_required_mask. The first use will by by powerpc.
> Note that this does add some dependency on the order in which files are
> visible here.
> 
> Signed-off-by:  Milton Miller <miltonm@....com>
> Signed-off-by: Nishanth Aravamudan <nacc@...ibm.com>
> Cc: linuxppc-dev@...ts.ozlabs.org
> Cc: linux-kernel@...r.kernel.org
> Cc: benh@...nel.crashing.org
> ---
>  include/linux/dma-mapping.h |    3 +++
>  1 files changed, 3 insertions(+), 0 deletions(-)
> 
> diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
> index ba8319a..d0e023b 100644
> --- a/include/linux/dma-mapping.h
> +++ b/include/linux/dma-mapping.h
> @@ -49,6 +49,9 @@ struct dma_map_ops {
>  	int (*mapping_error)(struct device *dev, dma_addr_t dma_addr);
>  	int (*dma_supported)(struct device *dev, u64 mask);
>  	int (*set_dma_mask)(struct device *dev, u64 mask);
> +#ifdef ARCH_HAS_DMA_GET_REQUIRED_MASK
> +	u64 (*get_required_mask)(struct device *dev);
> +#endif
>  	int is_phys;
>  };

If you add get_required_mask to dma_map_ops, we should clean up ia64
too and implement the generic proper version in
dma-mapping-common.h. Then we kill ARCH_HAS_DMA_GET_REQUIRED_MASK
ifdef hack. Otherwise, I don't think it makes sense to add this to
dma_map_ops.
--
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