linux-kernel - Re: [PATCH v2 2/6] PCI/MSI: Factor out pci_get_msi

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Message-ID: <20130906233205.GF12956@google.com>
Date:	Fri, 6 Sep 2013 17:32:05 -0600
From:	Bjorn Helgaas <bhelgaas@...gle.com>
To:	Tejun Heo <tj@...nel.org>
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>,
	"linux-ide@...r.kernel.org" <linux-ide@...r.kernel.org>,
	Ingo Molnar <mingo@...nel.org>, Joerg Roedel <joro@...tes.org>,
	Jan Beulich <JBeulich@...e.com>
Subject: Re: [PATCH v2 2/6] PCI/MSI: Factor out pci_get_msi_cap() interface

On Fri, Sep 06, 2013 at 12:06:21PM -0400, Tejun Heo wrote:
> Hello, Bjorn.
> 
> On Fri, Sep 06, 2013 at 10:01:38AM -0600, Bjorn Helgaas wrote:
> > Sorry, I haven't jumped in here yet because I saw your discussion and
> > was hoping you guys would figure something out without my help.  It
> > will take me a few hours to look into this and come up with anything
> > constructive to say.
> > 
> > I do remember disliking the complicated interface of
> > pci_enable_msi_block() (return negative errno, return positive "we
> > might be able to do this" values, or zero), but I'll have to do some
> > more research before I can say much more than that.
> 
> According to Alexander, it doesn't even seem like we have any actual
> use case for the positive return numbers.  I say just rip it out and
> do the regular 0/-errno all the way through.

I agree, that would be much simpler.

I propose that you rework it that way, and at least find out what
(if anything) would break if we do that.  Or maybe we just give up
some optimization; it would be nice to quantify that, too.

Bjorn
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