linux-kernel - Re: [PATCH v8 2/2] ARM: Enable selection of SMP operations at boot time

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Message-ID: <alpine.DEB.2.02.1304261629300.4180@kaball.uk.xensource.com>
Date:	Fri, 26 Apr 2013 16:36:37 +0100
From:	Stefano Stabellini <stefano.stabellini@...citrix.com>
To:	Nicolas Pitre <nicolas.pitre@...aro.org>
CC:	Will Deacon <will.deacon@....com>,
	Stefano Stabellini <Stefano.Stabellini@...citrix.com>,
	"xen-devel@...ts.xensource.com" <xen-devel@...ts.xensource.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"arnd@...db.de" <arnd@...db.de>,
	"rob.herring@...xeda.com" <rob.herring@...xeda.com>,
	"linux@....linux.org.uk" <linux@....linux.org.uk>,
	"olof@...om.net" <olof@...om.net>, Jon Medhurst <tixy@...aro.org>
Subject: Re: [PATCH v8 2/2] ARM: Enable selection of SMP operations at boot
 time

On Thu, 25 Apr 2013, Nicolas Pitre wrote:
> On Thu, 25 Apr 2013, Will Deacon wrote:
> 
> > On Wed, Apr 24, 2013 at 07:40:19PM +0100, Stefano Stabellini wrote:
> > > From: Jon Medhurst <tixy@...aro.org>
> > > 
> > > Add a new 'smp_init' hook to machine_desc so platforms can specify a
> > > function to be used to setup smp ops instead of having a statically
> > > defined value.  The hook must return true when smp_ops are initialized.
> > > If false the static mdesc->smp_ops will be used by default.
> > > 
> > > Signed-off-by: Jon Medhurst <tixy@...aro.org>
> > > Signed-off-by: Nicolas Pitre <nicolas.pitre@...aro.org>
> > > Signed-off-by: Stefano Stabellini <stefano.stabellini@...citrix.com>
> > > Reviewed-by: Santosh Shilimkar <santosh.shilimkar@...com>
> > > ---
> > >  arch/arm/include/asm/mach/arch.h |    4 ++++
> > >  arch/arm/kernel/setup.c          |   10 ++++++----
> > >  2 files changed, 10 insertions(+), 4 deletions(-)
> > 
> > [...]
> > 
> > >  	if (is_smp()) {
> > > -		if (psci_smp_available())
> > > -			smp_set_ops(&psci_smp_ops);
> > > -		else if (mdesc->smp)
> > > -			smp_set_ops(mdesc->smp);
> > > +		if (!mdesc->smp_init || !mdesc->smp_init()) {
> > 
> > Minor nit, but this feels backwards to me. We usually return 0 on success,
> > yet we're saying here that if mdesc->smp_init() returns 0, then we go and
> > override the smp ops.
> 
> It doesn't return 0, but true or false.  So, semantically, if ->smp_init 
> returns false, that means it didn't initialize anything.

In absence of other comments, I am going to leave as it is now.
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