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Subject: Re: [RFC/PATCH 14/16] MPIC MSI backend
From: Michael Ellerman <michael@ellerman.id.au>
To: Benjamin Herrenschmidt <benh@kernel.crashing.org>
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Date: Sat, 27 Jan 2007 17:54:11 +1100
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Cc: Grant Grundler <grundler@parisc-linux.org>,
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	shaohua.li@intel.com, linux-pci@atrey.karlin.mff.cuni.cz,
	"David S.Miller" <davem@davemloft.net>, Brice Goglin <brice@myri.com>
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On Sat, 2007-01-27 at 09:08 +1100, Benjamin Herrenschmidt wrote:
> > >From that comes our need for a data structure to map from an irq to a
> > msi data structure in a generic fashion, because we don't just program
> > the pci card and forget about it.  From those requirements comes our
> > need for a little bit more complete support of the features of the
> > hardware that Michaels implementation.
>=20
> Well, we need to go from pci_dev -> MSI and from linux irq_desc ->
> MSI... for now, we can get away without the later on powerpc, but I
> understand that intel needs that. The initial intel code used an array
> of NR_IRQs, but that sucks. What I remember of your patch is that they
> were using chip_data in irq_desc.

There's still an array of NR_IRQs msi_desc*, which are also attached to
the irq_desc.

The msi_desc is allocated and immediately attached to the irq_desc. Then
later it gets hooked into the array (attach_msi_entry) - I don't
understand why both methods are necessary - they both require the irq.

cheers

--=20
Michael Ellerman
OzLabs, IBM Australia Development Lab

wwweb: http://michael.ellerman.id.au
phone: +61 2 6212 1183 (tie line 70 21183)

We do not inherit the earth from our ancestors,
we borrow it from our children. - S.M.A.R.T Person

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