Leon Romanovsky <leon@xxxxxxxxxx> writes: > From: Christoph Hellwig <hch@xxxxxx> > > Add an explanation of the newly added IOVA-based mapping API. > > Signed-off-by: Christoph Hellwig <hch@xxxxxx> > Signed-off-by: Leon Romanovsky <leonro@xxxxxxxxxx> > --- > Documentation/core-api/dma-api.rst | 70 ++++++++++++++++++++++++++++++ > 1 file changed, 70 insertions(+) > > diff --git a/Documentation/core-api/dma-api.rst b/Documentation/core-api/dma-api.rst > index 8e3cce3d0a23..6095696a65a7 100644 > --- a/Documentation/core-api/dma-api.rst > +++ b/Documentation/core-api/dma-api.rst > @@ -530,6 +530,76 @@ routines, e.g.::: > .... > } > > +Part Ie - IOVA-based DMA mappings > +--------------------------------- > + > +These APIs allow a very efficient mapping when using an IOMMU. They are an > +optional path that requires extra code and are only recommended for drivers > +where DMA mapping performance, or the space usage for storing the DMA addresses > +matter. All the consideration from the previous section apply here as well. > + > +:: > + > + bool dma_iova_try_alloc(struct device *dev, struct dma_iova_state *state, > + phys_addr_t phys, size_t size); > + > +Is used to try to allocate IOVA space for mapping operation. If it returns > +false this API can't be used for the given device and the normal streaming > +DMA mapping API should be used. The ``struct dma_iova_state`` is allocated > +by the driver and must be kept around until unmap time. So, I see that you have nice kernel-doc comments for these; why not just pull them in here with a kernel-doc directive rather than duplicating the information? Thanks, jon
