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Re: Time to make PCI_MSI default y ?

To: Ralf Baechle <>
Subject: Re: Time to make PCI_MSI default y ?
From: Benjamin Herrenschmidt <>
Date: Wed, 25 Nov 2009 08:09:12 +1100
Cc: Michael Ellerman <>, linux-pci <>,, "tony.luck" <>,, "David S.Miller" <>, Thomas Gleixner <>,, Peter Anvin <>,, David Daney <>
In-reply-to: <>
Original-recipient: rfc822;
References: <1259030388.20596.5.camel@concordia> <>
On Tue, 2009-11-24 at 12:53 +0000, Ralf Baechle wrote:
> On Tue, Nov 24, 2009 at 01:39:48PM +1100, Michael Ellerman wrote:
> > Having just hit a build-break caused by a distro building with
> > PCI_MSI=n, I set out to make it default y for powerpc. Unfortunately
> > that's not possible, because it's in drivers/pci/Kconfig.
> > 
> > So is it time to make it default y for everyone? It seems to me having
> > it off is more likely to cause problems than having it on these days,
> > though I'm not sure if that is true for all archs.
> > 
> > An arch that really didn't want it default y could conditionally select
> > ARCH_SUPPORTS_MSI, like x86 does already.
> On MIPS the age of MSI only recently started; once single platform (Cavium)
> out of all the many uses it.  Cavium does a "select ARCH_SUPPORTS_MSI" but
> not "select PCI_MSI" because not all platform variants actually have PCI.
> We should  not give a user a chance to select something wrong in kconfig
> thus automatically as many options for a platform as possible is a good
> thing - after all the kconfig dialog for any given platfrom has become
> painfully long.  And we really should have to avoid users having to know
> that the Frobnic 2000 they're trying to upgrade the kernel for requires
> MSI to work ...

Still... select has nasty issues. I think default y is fine here. For
platforms that don't need it, make sure their defconfigs don't have it

Or maybe default y if (X86 || PPC)


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