Re: [PATCH v4 1/1] iommu-api: Add map_sg/unmap_sg functions

[Olav Haugan <ohaugan-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org>]

On 8/6/2014 11:24 PM, Thierry Reding wrote:
> On Wed, Aug 06, 2014 at 04:28:45PM -0700, Olav Haugan wrote:
>> On 8/6/2014 1:17 PM, Joerg Roedel wrote:
>>> On Wed, Aug 06, 2014 at 10:08:55AM -0700, Olav Haugan wrote:
>>>> so you are suggesting that I check in "bus_set_iommu()" whether the
>>>> driver has set the map_sg/unmap_sg function pointers or not and if not
>>>> set it to the default? Is bus_set_iommu() the only way drivers can set
>>>> up the callbacks?
>>>
>>> This doesn't work as the iommu_ops are now const. You have to either
>>> update the iommu drivers individually to point to the default function,
>>> or you do the check in the API function itself and fall back to the
>>> default it no call-back is provided.
>>>
>>
>> Ok, then I think it is better to just leave the fallback where it is now
>> in the function itself.
> 
> What Konrad was suggesting is what I also proposed. The idea is to
> implement a fallback as standalone function, then make all drivers use
> that by default in the struct iommu_ops that they register. When drivers
> implement an optimized version they can simply replace the fallback
> implementation with their own.
> 

Ok, I can do that. I misunderstood the point of the fallback. I thought
the point of the fallback was to catch drivers that forget/neglect to
implement this callback. If that is not a concern I will update my patch
to create a separate function that I will point all existing drivers to.

Thanks,

Olav

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