linux-kernel - Re: [PATCH v5 3/3] PM: Introduce Intel PowerClamp Driver

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Date:	Fri, 4 Jan 2013 08:51:13 -0800
From:	jacob pan <jacob.jun.pan@...ux.intel.com>
To:	Joe Perches <joe@...ches.com>
Cc:	Linux PM <linux-pm@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Rafael Wysocki <rafael.j.wysocki@...el.com>,
	Len Brown <len.brown@...el.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...e.hu>,
	Zhang Rui <rui.zhang@...el.com>, Rob Landley <rob@...dley.net>,
	Arjan van de Ven <arjan@...ux.intel.com>,
	Paul McKenney <paulmck@...ux.vnet.ibm.com>
Subject: Re: [PATCH v5 3/3] PM: Introduce Intel PowerClamp Driver

On Thu, 03 Jan 2013 19:51:04 -0800
Joe Perches <joe@...ches.com> wrote:

> On Thu, 2013-01-03 at 07:10 -0800, Jacob Pan wrote:
> > Intel PowerClamp driver performs synchronized idle injection across
> > all online CPUs. The goal is to maintain a given package level
> > C-state ratio.
> 
> []
> 
> > +static int window_size_set(const char *arg, const struct
> > kernel_param *kp) +{
> > +	int ret = 0;
> > +	unsigned long new_window_size;
> > +
> > +	ret = kstrtoul(arg, 10, &new_window_size);
> > +	if (ret)
> > +		goto exit_win;
> > +	if (new_window_size > 10 || new_window_size < 2) {
> > +		pr_err("Invalid window size %lu, between 2-10\n",
> > +			new_window_size);
> > +		ret = -EINVAL;
> > +	}
> > +
> > +	window_size = new_window_size;
> 
> Possible assignment of known invalid windows size?
> Maybe you should add
> 	goto exit;
> after
> 	ret = -EINVAL;
> 
> or add
> 	new_window_size = clamp(new_window_size, 2ul, 10ul);
Good catch. The window size range 2-10 is somewhat arbitrary, greater
than 10 should also work just not recommended. I will reword that. But
it is good to clamp it as you suggested, i will do that for the
duration parameter also.

Thanks,

Jacob
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