linux-kernel - Re: [PATCH 22/34] dma-mapping: add an arch_dma

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Date:   Fri, 2 Feb 2018 09:47:23 -0800
From:   Randy Dunlap <rdunlap@...radead.org>
To:     Christoph Hellwig <hch@....de>, iommu@...ts.linux-foundation.org
Cc:     Konrad Rzeszutek Wilk <konrad@...nok.org>,
        linux-alpha@...r.kernel.org, linux-snps-arc@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-c6x-dev@...ux-c6x.org,
        linux-cris-kernel@...s.com, linux-hexagon@...r.kernel.org,
        linux-ia64@...r.kernel.org, linux-m68k@...ts.linux-m68k.org,
        linux-metag@...r.kernel.org, Michal Simek <monstr@...str.eu>,
        linux-mips@...ux-mips.org, linux-parisc@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, patches@...ups.riscv.org,
        linux-s390@...r.kernel.org, linux-sh@...r.kernel.org,
        sparclinux@...r.kernel.org, Guan Xuetao <gxt@...c.pku.edu.cn>,
        x86@...nel.org, linux-arch@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 22/34] dma-mapping: add an arch_dma_supported hook

On 01/12/2018 12:42 AM, Christoph Hellwig wrote:
> To implement the x86 forbid_dac and iommu_sac_force we want an arch hook
> so that it can apply the global options across all dma_map_ops
> implementations.
> 
> Signed-off-by: Christoph Hellwig <hch@....de>
> ---
>  arch/x86/include/asm/dma-mapping.h |  3 +++
>  arch/x86/kernel/pci-dma.c          | 19 ++++++++++++-------
>  include/linux/dma-mapping.h        | 11 +++++++++++
>  3 files changed, 26 insertions(+), 7 deletions(-)

> diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
> index 88bcb1a8211d..d67742dad904 100644
> --- a/include/linux/dma-mapping.h
> +++ b/include/linux/dma-mapping.h
> @@ -576,6 +576,14 @@ static inline int dma_mapping_error(struct device *dev, dma_addr_t dma_addr)
>  	return 0;
>  }
>  
> +/*
> + * This is a hack for the legacy x86 forbid_dac and iommu_sac_force. Please
> + * don't use this is new code.

                     in new code.

> + */
> +#ifndef arch_dma_supported
> +#define arch_dma_supported(dev, mask)	(1)
> +#endif


-- 
~Randy