Re: [PATCH v5 4/9] PCI/P2PDMA: Export pci_p2pdma_map_type() function

Christoph Hellwig
2025-10-20T12:29:09Z

On Fri, Oct 17, 2025 at 09:14:47AM -0300, Jason Gunthorpe wrote:
> On Thu, Oct 16, 2025 at 11:31:53PM -0700, Christoph Hellwig wrote:
> >
> > Nacked-by: Christoph Hellwig <hch@lst.de>
> >
> > As explained to you multiple times, pci_p2pdma_map_type is a low-level
> > helper that absolutely MUST be wrapper in proper accessors.
>
> You never responded to the discussion:
>
> https://lore.kernel.org/all/20250727190252.GF7551@nvidia.com/
>
> What is the plan here? Is the new DMA API unusable by modules? That
> seems a little challenging.

Yes. These are only intended to be wrapped by subsystems.

> It looks like there is a simple enough solution here. I wanted to
> tackle this after, but maybe it is small enough to do it now.
>
> dmabuf should gain some helpers like BIO has to manage its map/unmap
> flows, so lets put a start of some helpers in
> drivers/dma/dma-mapping.c (or whatever). dmabuf is a built in so it
> can call the function without exporting it just like block and hmm are
> doing.

Yes, that sounds much better. And dmabuf in general could use some
deduplicating of their dma mapping patterns (and eventual fixing).