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

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

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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.

Thierry

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