Linux-kernel mailing list archive 1999-37,: Re: [patch] pci probing

# Re: [patch] pci probing

Jeff Garzik (jgarzik@pobox.com)
Sun, 12 Sep 1999 17:20:25 -0400

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Donald Becker wrote:
> My approach specifically does *not* do request_region(). That occurs only
> when the device is recognized and named. For network drivers that's the
> "eth0" name, which isn't known at probe1() time. In some cases a probe1()
> routine will reject the device, and the region shouldn't be registered.

If resource code is to work in the kernel, presumeably you should
__request_region() [note leading '__'] before ioremap, or talking to
that hardware mem or I/O region at all. Including ISA-style probing to
various ports, and other init-only tasks like that.

> > I outlined in my previous mail why your implementation is inadequate for
> > some cases, which IMHO are becoming more common at new devices are
> > released. For example, multiple PCI base addresses are becoming more
> > and more common. Why not handle all the base addresses in a loop,
> > instead of just simply handling the first one? Why not also add
> > __request_region code also? That's a source of ifdefs. etc.
>
> There are nightmare devices that use all five base address registers. But
> they usually full of other nightmare design decisions that prevents any
> regular scheme from working. Most non-bridge devices have matching memory
> and I/O space mappings, and sometime use the boot ROM register. I see fewer
> exceptions to this than when PCI was new.

Multiple base addresses is common for video cards and on the Meteor-II
framegrabber at least. The audio codec built into my motherboard has
two I/O ports. And my IDE controller has a single I/O base at PCI
region #4!

What is your suggestion for a solution to the issues I outlined, two
e-mails previous? Have two sets of pci scan code, one that works well
with video drivers, and one that works well with net drivers? I do not
think that is optimal.

IMHO It would be nice to either expand your pci-scan code, which is fine
with me, or make my suggested code handle some of the features it
currently lacks, like CardBus support via the cb hooks and
drv_register/unregister scheme. If I have time tonight, I'll see if I
can post a patch which does this.

Regards,

Jeff

    --
    Custom driver development	|    Never worry about theory as long
    Open source programming		|    as the machinery does what it's
    				|    supposed to do.  -- R. A. Heinlein

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