Re: remove the ->mapping_error method from dma_map_ops V2
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- To: Russell King - ARM Linux <linux@xxxxxxxxxxxxxxx>
- Subject: Re: remove the ->mapping_error method from dma_map_ops V2
- From: Joerg Roedel <joro@xxxxxxxxxx>
- Date: Fri, 23 Nov 2018 14:03:13 +0100
- Cc: Robin Murphy <robin.murphy@xxxxxxx>, Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>, Christoph Hellwig <hch@xxxxxx>, linux-arch@xxxxxxxxxxxxxxx, linux-alpha@xxxxxxxxxxxxxxx, linux-ia64@xxxxxxxxxxxxxxx, linux-parisc@xxxxxxxxxxxxxxx, David Woodhouse <dwmw2@xxxxxxxxxxxxx>, the arch/x86 maintainers <x86@xxxxxxxxxx>, Linux List Kernel Mailing <linux-kernel@xxxxxxxxxxxxxxx>, iommu@xxxxxxxxxxxxxxxxxxxxxxxxxx, jdmason@xxxxxxxx, xen-devel@xxxxxxxxxxxxxxxxxxxx, linux-arm-kernel@xxxxxxxxxxxxxxxxxxx, m.szyprowski@xxxxxxxxxxx
- In-reply-to: <20181123110155.GR30658@n2100.armlinux.org.uk>
- References: <20181122140320.24080-1-hch@lst.de> <CAHk-=wh=_T=A53+o4zLNbKio43LGqVDb0KCbWPDvAg54bRDmWw@mail.gmail.com> <20181122170715.GI30658@n2100.armlinux.org.uk> <CAHk-=wgfGzXuDAKFQPdzMib3QCRHfSTsy5=gLU-WCoya+Ym+1A@mail.gmail.com> <11829e3c-7302-f821-cf5c-863e5267a17b@arm.com> <20181123104918.GE1586@8bytes.org> <20181123110155.GR30658@n2100.armlinux.org.uk>
- User-agent: Mutt/1.9.4 (2018-02-28)
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.
Regards,
Joerg
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