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Date: Thu, 05 Jun 2003 04:17:38 -0700
From: Terry Lambert <tlambert2@mindspring.com>
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To: "David P. Reese Jr." <daver@gomerbud.com>
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cc: current@freebsd.org
Subject: Re: viapropm doesnt like sys/dev/pci.c rev 1.214
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"David P. Reese Jr." wrote:
> > > A snip of code from sys/dev/pci/pci.c:pci_enable_io_method():
> > >
> > >         pci_set_command_bit(dev, child, bit);
> > >         command = PCI_READ_CONFIG(dev, child, PCIR_COMMAND, 2);
> > >         if (command & bit)
> > >                 return (0);
> > >         device_printf(child, "failed to enable %s mapping!\n", error);
> > >         return (ENXIO);
> > >
> > > Because the viapropm's command register bits will always read as zero,
> > > this code will always fail when trying to enable port mapping.
[ ... ]
> 
> How about adding another flag to bus_alloc_resource() which would signal
> that we are not to check the value of the command register after calling
> pci_set_command_bit().
> 
> RF_WILLFAIL?
> 
> After pci_enable_io_method() gets swallowed into pci_alloc_resource(),
> this would be pretty easy because the flag would be in scope when we
> check the value of the command register.
> 
> I can do so this weekend if anyone thinks this is worthwhile.

How about RF_DONTCHECK or RF_ALWAYSWORKS?  It better implies
what's happening here, since you're going to assume success in
the face of diagnostics to the contrary.

So instead of:

	if (flag)
		return (0);
	command = PCI_READ_CONFIG(dev, child, PCIR_COMMAND, 2);
	if (command & bit)
		return (0);
	device_printf(child, "failed to enable %s mapping!\n", error);
	return (ENXIO);

You do:

	command = PCI_READ_CONFIG(dev, child, PCIR_COMMAND, 2);
	if ((command & bit) || flag)
		return (0);
	device_printf(child, "failed to enable %s mapping!\n", error);
	return (ENXIO);

Yeah, I know the disctinction is subtle, but there migh be other
PCI_READ_CONFIG() results later that people care about, besides
just this one bit, which *do* work on some other chip with the
same issue.

-- Terry