Re: [PATCH] PCI 64-bit API up for testing

[Richard Henderson <rth@twiddle.net>]

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On Tue, Aug 21, 2001 at 08:09:53AM -0700, David S. Miller wrote:
> ftp://ftp.kernel.org/pub/linux/kernel/people/davem/PCI64/

Here's bits for Alpha vs 2.4.9 + pci64 patch 3.  It's not been
tested seriously, since I have no 64-bit capable devices.  But it
looks mostly ok, and continues to boot on a number of machines.

Something that should be mentioned in the documentation for someone
implementing these functions is that drivers will call the pci64
interfaces *even if* pci_dac_cycles_ok returns false, which means
that one has to remember what decisions were made in that function.

I'm undecided on whether we should consider such nonsense illegal.

On the one hand, it clutters up the pci mapping functions, and it
is easy to forget all the proper checks.  The sparc64 version, for
instance, will do the wrong thing if PCI_DMA_FLAG_HUGE_MAPS is set
and the device supports less than 64 bits of addressing.

On the other hand, I can also see that requiring that the driver
call the correct sets of functions based on what mode it's in will
clutter up driver source.  Given that there are more drivers than
architectures, it makes sense to keep them as clean as may be.


r~

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