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

[Olav Haugan <ohaugan@codeaurora.org>]

On 10/15/2014 2:16 AM, Thierry Reding wrote:
> 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?
>

I am fine with that. Joerg?

Thanks,

.Olav

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