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Subject: Re: [RFC/PATCH 4/7] Powerpc MSI implementation
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Matthew Wilcox <matthew@wil.cx>
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Date: Wed, 08 Nov 2006 07:39:18 +1100
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On Tue, 2006-11-07 at 13:07 -0700, Matthew Wilcox wrote:
> On Tue, Nov 07, 2006 at 06:21:23PM +1100, Michael Ellerman wrote:
> > We currently (ab)use the pci_dev to store our msi_info structure. We
> > were hoping to stash it in the pci_dn, but that's not a goer, so the
> > pci_dev seems like the right place, even though it seems naughty to
> > bloat generic structs.
> 
> We have the per-irq void *chip_data; could this be the right place to
> keep it instead?  That way, it won't take up space in the pci_dev for
> devices which don't use MSI.
> 
> Or do you rely on mpic_from_irq() working for MSI interrupts too?

Yes, we rely on that.

The chip_data is for use by the IRQ controller. In our cases, for some
controllers at least, MSIs are just an add-on to an existing controller
(they toggle existing inputs).

In general, I think it just make sense to have pci_dev contain MSI
tracking data for the device though.

Cheers,
Ben.