Re: [PATCH v5 1/1] iommu-api: Add map_sg/unmap_sg functions

[Thierry Reding <thierry.reding@gmail.com>]

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On Mon, Oct 06, 2014 at 12:02:47PM -0700, Olav Haugan wrote:
> On 9/25/2014 10:01 AM, Joerg Roedel wrote:
> >On Mon, Aug 11, 2014 at 03:45:50PM -0700, Olav Haugan wrote:
> >>+static inline int iommu_map_sg(struct iommu_domain *domain, unsigned long iova,
> >>+			       struct scatterlist *sg, unsigned int nents,
> >>+			       int prot, unsigned long flags)
> >>+{
> >>+	return domain->ops->map_sg(domain, iova, sg, nents, prot, flags);
> >>+}
> >>+
> >>+static inline int iommu_unmap_sg(struct iommu_domain *domain,
> >>+				 unsigned long iova, size_t size,
> >>+				 unsigned long flags)
> >>+{
> >>+	return domain->ops->unmap_sg(domain, iova, size, flags);
> >>+}
> >
> >I have thought a little bit more about this interface and think that it
> >would be better to just return a size_t from iommu_map_sg().  The
> >function returns the amount of address space mapped by it, 0 in the
> >worst case.
> >
> >This makes it easy to unmap the region just with
> >iommu_unmap(domain, iova, size) in the end and removing the need for a
> >new iommu_unmap_sg() function. Also the error-path of the map_sg
> >call-backs becomes easier as the function then just returns the amount
> >of address-space already mapped before the error happened.
> >
> >So the prototype would be:
> >
> >	size_t iommu_map_sg(struct iommu_domain *domain,
> >			    unsigned long iova,
> >			    struct scatterlist *sg,
> >			    unsigned int nents,
> >			    int prot);
> >
> >(as I said before, the flags parameter should not be added by this
> >  patch-set).
> >
> 
> Ok, sounds good. I'll post v6 soon.

Perhaps make the return value ssize_t so that we can propagate errors?

Thierry

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