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

[Joerg Roedel <joro-zLv9SwRftAIdnm+yROfE0A@public.gmane.org>]

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).


	Joerg