linux-kernel - Re: [PATCH] Cpufreq: Change sysfs interface cpuinfo_cur

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Message-ID: <1521595.q8BSAikk1K@vostro.rjw.lan>
Date:	Mon, 25 Nov 2013 13:14:54 +0100
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	Lan Tianyu <tianyu.lan@...el.com>
Cc:	Viresh Kumar <viresh.kumar@...aro.org>, hg197@....de,
	"cpufreq@...r.kernel.org" <cpufreq@...r.kernel.org>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] Cpufreq: Change sysfs interface cpuinfo_cur_freq access privilege

On Monday, November 25, 2013 07:55:33 PM Lan Tianyu wrote:
> On 11/25/2013 07:26 PM, Rafael J. Wysocki wrote:
> > On Monday, November 25, 2013 01:33:39 PM Lan Tianyu wrote:
> >> On 2013年11月25日 12:30, Viresh Kumar wrote:
> >>> On 25 November 2013 08:23, Lan Tianyu <tianyu.lan@...el.com> wrote:
> >>>> Currently, cpuinfo_cur_freq is only accessible for root user while
> >>>> other cpufreq sysfs interfaces(E,G scaling_cur_freq) are available
> >>>> to ordinary user. This seems make no sense. This patch is to change
> >>>> it.
> >>>
> >>> There is nothing wrong with the code and so this is more of a design
> >>> change..
> >>>
> >>> Probably Rafael can help us here as cpufreq_cur_freq will read stuff
> >>> directly from hardware instead of using cached value in software.
> >>
> >> I think so, too. I also tried to checking the reason of the privilege by
> >> git log but the code was there before linux kernel being migrated to git
> >> repository.
> >
> > And it has always behaved in the same way?  Then I wouldn't change it.
> >
> 
> It has been there since 2.6.12-rc2 or more early. But the 
> cpuinfo_cur_freq is read-only and seems no harmful.

If it reads things directly from hardware, it may not be totally neutral.

Thanks!

-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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