[RFC PATCH v2 06/11] dma-direct: Support PCI P2PDMA pages in dma-direct map_sg

[Christoph Hellwig]

On Fri, Mar 12, 2021 at 11:27:46AM -0700, Logan Gunthorpe wrote:
> So then we reject the patches that make that change. Seems like an odd
> argument to say that we can't do something that won't cause problems
> because someone might use it as an example and do something that will
> cause problems. Reject the change that causes the problem.

No, the problem is a mess of calling conventions.  A calling convention
returning 0 for error, positive values for success is fine.  One returning
a negative errno for error and positive values for success is fine a well.
One returning 0 for the usual errors and negativ errnos for an unusual
corner case is just a complete mess.