Re: [Xen-devel] [PATCH v4 3/7] [RFC] arm/arm64: introduce is_dma_coherent

[Will Deacon <will.deacon@xxxxxxx>]

On Mon, Oct 13, 2014 at 12:16:14PM +0100, Stefano Stabellini wrote:
> On Fri, 10 Oct 2014, Stefano Stabellini wrote:
> > On Fri, 10 Oct 2014, Will Deacon wrote:
> > > On Fri, Oct 10, 2014 at 12:51:44PM +0100, Stefano Stabellini wrote:
> > > > Introduce a function to check whether a device is dma coherent.
> > > > 
> > > > Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
> > > > CC: linux@xxxxxxxxxxxxxxxx
> > > > CC: catalin.marinas@xxxxxxx
> > > > CC: will.deacon@xxxxxxx
> > > > CC: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
> > > > ---
> > > >  arch/arm/include/asm/dma-mapping.h   |    6 ++++++
> > > >  arch/arm64/include/asm/dma-mapping.h |    5 +++++
> > > >  2 files changed, 11 insertions(+)
> > > > 
> > > > diff --git a/arch/arm/include/asm/dma-mapping.h 
> > > > b/arch/arm/include/asm/dma-mapping.h
> > > > index c45b61a..bededbb 100644
> > > > --- a/arch/arm/include/asm/dma-mapping.h
> > > > +++ b/arch/arm/include/asm/dma-mapping.h
> > > > @@ -126,6 +126,12 @@ static inline int set_arch_dma_coherent_ops(struct 
> > > > device *dev)
> > > >         set_dma_ops(dev, &arm_coherent_dma_ops);
> > > >         return 0;
> > > >  }
> > > > +
> > > > +static inline bool is_dma_coherent(struct device *dev)
> > > > +{
> > > > +    return (__generic_dma_ops(dev) == &arm_coherent_dma_ops);
> > > > +}
> > > 
> > > Hmm, what about the IOMMU ops?
> > 
> > Maybe I should check __generic_dma_ops(dev) != &arm_dma_ops?
> > Do you have any better suggestions?
> 
> ping?

Without any clear idea about why this is needed or how it's used, I don't
have any better ideas.

Will

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