linux-kernel - Re: [patch 1/8] 2.6.22-rc3 perfmon2 : Barcelona CPU detection

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Date:	Thu, 21 Jun 2007 12:29:02 +0200
From:	"Robert Richter" <robert.richter@....com>
To:	"David Rientjes" <rientjes@...gle.com>
cc:	"Stephane Eranian" <eranian@....hp.com>,
	"Andi Kleen" <andi@...stfloor.org>, linux-kernel@...r.kernel.org
Subject: Re: [patch 1/8] 2.6.22-rc3 perfmon2 : Barcelona CPU detection

On 20.06.07 12:45:35, David Rientjes wrote:
> On Wed, 20 Jun 2007, Robert Richter wrote:
> 
> > Index: linux-2.6.22-rc3/arch/x86_64/perfmon/perfmon_k8.c
> > ===================================================================
> > --- linux-2.6.22-rc3.orig/arch/x86_64/perfmon/perfmon_k8.c
> > +++ linux-2.6.22-rc3/arch/x86_64/perfmon/perfmon_k8.c
> > @@ -307,7 +307,12 @@ static int pfm_k8_probe_pmu(void)
> >  		return -1;
> >  	}
> >  
> > -	if (current_cpu_data.x86 != 15) {
> > +	switch (current_cpu_data.x86) {
> > +	case 15:
> > +	case 16:
> > +		PFM_INFO("found family=%d", current_cpu_data.x86);
> > +		break;
> > +	default:
> >  		PFM_INFO("unsupported family=%d", current_cpu_data.x86);
> >  		return -1;
> >  	}
> 
> This still shouldn't be a switch clause because you're hiding the return 
> -1; in the default label.  I think it would be better to write:
> 
> 	if (current_cpu_data.x86 == 15 || current_cpu_data.x86 == 16)
> 		PFM_INFO("found family=%d", current_cpu_data.x86);
> 	else {
> 		PFM_INFO("unsupported family=%d", current_cpu_data.x86);
> 		return -1;
> 	}
> 
> 

With the next CPU family the if condition would be too long while
adding another case statement is more readable. Anyway, things always
have 2 sides and I understand your concerns.

-Robert


-- 
AMD Saxony, Dresden, Germany
Operating System Research Center
email: robert.richter@....com



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