linux-kernel - Re: [PATCH v3 -tip x86/apic 1/2] PCI/MSI: Allocate as many multiple-MSIs as requested

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Message-ID: <20130605212841.GB5816@breakpoint.cc>
Date:	Wed, 5 Jun 2013 23:28:41 +0200
From:	Sebastian Andrzej Siewior <sebastian@...akpoint.cc>
To:	Bjorn Helgaas <bhelgaas@...gle.com>
Cc:	Alexander Gordeev <agordeev@...hat.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"x86@...nel.org" <x86@...nel.org>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	Yinghai Lu <yinghai@...nel.org>,
	Joerg Roedel <joro@...tes.org>,
	Jan Beulich <JBeulich@...e.com>, Ingo Molnar <mingo@...hat.com>
Subject: Re: [PATCH v3 -tip x86/apic 1/2] PCI/MSI: Allocate as many
 multiple-MSIs as requested

-Suresh

On Wed, Jun 05, 2013 at 03:09:34PM -0600, Bjorn Helgaas wrote:
> 
> Alexander had an example device that advertised 16 vectors, but the
> driver knew that it could only generate 6.  That's a case where we
> can't compute 'multiple' from 'nvec' (assuming the driver supplies
> 'nvec == 6').  If we just rounded up to compute 'multiple', I think
> we'd compute 8 instead of 16.

Sure, but as I said: the only place where 'multiple' is computed / written
it is doing the round-up thingy.

> > While nitpicking, 'nvec' might deserve a better comment than 'number of
> > messages' since it holds the number of allocated interrupts. :)
> 
> I did change the name 'nvec' to 'nvec_used', which should help a bit.
> But I agree that it's still somewhat confusing.
> 
> BTW, the patches actually in my tree are at
> http://git.kernel.org/cgit/linux/kernel/git/helgaas/pci.git/log/?h=pci/alexander-msi
> (I tweaked this name and some comments slightly).

'nvec_used' is better the comment next to it is still wrong I think.

> Bjorn

Sebastian
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