On Mon, Mar 16, 2020 at 10:41:42AM +0100, Christian König wrote:
> Well I would prefer if the drivers can somehow express their requirements
> and get IOVA structures already in the form they need.
>
> Converting the IOVA data from one form to another is sometimes quite costly.
> Especially when it is only temporarily needed.
We basically have two ways to generate the IOVA:
- a linear translation for the direct mapping case or some dumb IOMMU
drivers - in that case case there is a 1:1 mapping between input
segments and output segments in DMA mapping
- a non-trivial IOMMU where all aligned segments are merged into
a single IOVA range
So I don't really see how the dma layer could help much with any
limitation beyond existing max size and dma boundary ones.
