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Re: [Xen-devel] remove the ->mapping_error method from dma_map_ops V2

On Fri, Nov 23, 2018 at 11:01:55AM +0000, Russell King - ARM Linux wrote:
> Yuck.  So, if we have a 4GB non-PAE 32-bit system, or a PAE system
> where we have valid memory across the 4GB boundary and no IOMMU,
> we have to reserve the top 4K page in the first 4GB of RAM?

But that is only needed when dma_addr_t is 32bit anyway, no?

> Rather than inventing magic cookies like this, I'd much rather we
> sanitised the API so that we have functions that return success or
> an error code, rather than trying to shoe-horn some kind of magic
> error codes into dma_addr_t and subtly break systems in the process.

Sure, but is has the obvious downside that we need to touch every driver
that uses these functions, and that are probably a lot of drivers.



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