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

[Rob Clark]

On Mon, Aug 18, 2014 at 10:07 AM, joro at 8bytes.org <joro at 8bytes.org> wrote:
> On Tue, Aug 12, 2014 at 09:56:11AM -0700, Olav Haugan wrote:
>> On 8/12/2014 3:48 AM, Rob Clark wrote:
>> > iirc, one plan for 'flags' was some sort of DONT_FLUSH_TLB flag for
>> > drivers which wanted to map/unmap N buffers with a single flush at the
>> > end.  There might have been some other usages envisioned.
>>
>> Yes, that was the original intent of the flags for now. I am sure we can
>> find other uses for this in the future.
>
> Do you have anything else in mind already besides the DONT_FLUSH_TLB
> flag?
>
> How is the IOTLB supposed to be flushed when this flag is used?
>

well, I was thinking one of two ways:

1) add new flush() vfunc.. this, I think, would be most convenient for
drivers using this feature
2) or driver simply doesn't set DONT_FLUSH_TLB flag on the last
{map,unmap}..  that would be slightly more awkward to use, but would
avoid adding a new vfunc

BR,
-R

>         Joerg
>