Re: [PATCH v9] block: Add n64 cart driver

Christoph Hellwig
2021-01-22T18:30:49Z

On Fri, Jan 22, 2021 at 08:01:17PM +0200, Lauri Kasanen wrote:
> On Fri, 22 Jan 2021 09:11:20 -0800
> Keith Busch <kbusch@kernel.org> wrote:
> > Each bio_vec segment is physically contiguous.
>
> What's the official way to get that buffer's physical address? I
> couldn't find any driver that does DMA to the bio buffer, to use as an
> example. Maybe used wrong keywords.

In Linux we never DMA to the physical address, but the DMA address.

For a bio with just a single bvec (that is a single contigous segment)
we have the dma_map_bvec helper that is only used by the nvme-pci
driver for special optimizations in the case of a single contigous
segment.