Re: pci_enable_msi() for everyone?

[Jeff Garzik <jgarzik@pobox.com>]

Benjamin Herrenschmidt wrote:
> > 	pci_enable(info on what to enable)
> >
> > so that drivers can specify ahead of time "don't enable PIO, only MMIO", 
> > "don't enable MMIO, only PIO", "don't use MSI", etc.  and add a 
> > pci_disable() to undo all of that.
> >
> > The more we add singleton functions like pci_enable_msi(), 
> > pci_set_master(), etc. the more I wish for a single function that 
> > handled all those details at one atomic point.  There is a lot of 
> > standard patterns that are hand-coded into every PCI driver's probe 
> > functions.
>
>
> Agreed, with the proper arch hook to deal with arch brokenness of
> course.
>
> That could be a bitmap. What I'm not 100% confident at this point is
> wether we want a bit per BAR or an "IO" bit and an "MMIO" bit. I think
> I'd rather go for the first one.

A bitmap is what I would start with.  But I would implement it as

	struct pci_enable_info {
		unsigned long flags;
	};

because I guarantee we'll want more flexibility as time goes on.

Honestly I can think of situations where one driver would want a bit per 
BAR, and many others would just need a single MMIO bit.  Don't forget 
legacy decoding too:  with -only- a bit per BAR, the driver cannot tell 
the PCI layer that disabling IO means disabling a legacy ISA region 
that's not listed in the PCI BARs.

	Jeff



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