[PATCH] PCI 64-bit API up for testing

[PATCH] PCI 64-bit API up for testing

[David S. Miller]

As discussed much of last week between Jens and myself,
we need a PCI 64-bit API to make progress in certain
areas.  It is needed for other reasons, but what Jens
is trying to solve exacerbates this need.

Jens's current highmem no-bounce patches include this
stuff, but we feel it is useful to distribute just these
changes independantly.  Especially for review and to acquire
help from port maintainers.

I held off until today because I wanted to convert a few
drivers first for two reasons:

1) To provide useful 64-bit driver examples.
2) To make sure the API worked and was usable.  A lot
   of details were not fleshed out until I actually tried
   to use the API I had initially created :-)

So this patch serves two purposes.  First, it's for review
and to get feedback from other hackers and driver authors.
Second, it is for platform authors so that they can send me
the updates for their port.

Most platforms which are simple and never have more than 4GB
ram will simply define the pci_*() routines to pci64_*(), make
pci_dac_cycles_ok() always return '0' and define dma64_addr_t
to be typedef'd to "u32".

If platform maintainers could do this and send me an incremental
diff, I would appreciate it.

Currently it is "ported" and tested on ix86 and Sparc64.

Get the latest at:

ftp://ftp.kernel.org/pub/linux/kernel/people/davem/PCI64/

I've moved the older zerocopy stuff, which used to be at
the top level under davem/, to:

ftp://ftp.kernel.org/pub/linux/kernel/people/davem/ZEROCOPY/

Later,
David S. Miller
davem@redhat.com

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

[Richard Henderson]

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

[David S. Miller]

Thanks tossing this together Richard.

I might swizzle the API a little bit after listening to feedback I
have gotten back so far, but I can easily munge your work into
whatever I end up with.

Later,
David S. Miller
davem@redhat.com