linux-kernel - Re: [PATCH] intel_menlo: max_state is unsigned, invalid test

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Date:	Mon, 03 Nov 2008 23:07:08 -0500 (EST)
From:	Len Brown <lenb@...nel.org>
To:	Andrew Morton <akpm@...ux-foundation.org>,
	Sujith Thomas <sujith.thomas@...el.com>,
	Zhang Rui <rui.zhang@...el.com>
Cc:	roel kluin <roel.kluin@...il.com>, len.brown@...el.com,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-acpi@...r.kernel.org
Subject: Re: [PATCH] intel_menlo: max_state is unsigned, invalid test



On Mon, 3 Nov 2008, Andrew Morton wrote:

> On Wed, 29 Oct 2008 17:06:47 -0400
> roel kluin <roel.kluin@...il.com> wrote:
> 
> > max_state is unsigned, so the test is invalid.
> > 
> > Signed-off-by: Roel Kluin <roel.kluin@...il.com>
> > ---
> > I think max_state can only become -1, no? then probably a different
> > patch is required.
> > I may not be able to respond for a few weeks.
> > 
> > diff --git a/drivers/misc/intel_menlow.c b/drivers/misc/intel_menlow.c
> > index e00a275..980171d 100644
> > --- a/drivers/misc/intel_menlow.c
> > +++ b/drivers/misc/intel_menlow.c
> > @@ -121,7 +121,7 @@ static int memory_set_cur_bandwidth(struct thermal_cooling_device *cdev,
> >  	if (memory_get_int_max_bandwidth(cdev, &max_state))
> >  		return -EFAULT;
> >  
> > -	if (max_state < 0 || state > max_state)
> > +	if (max_state == -1 || state > max_state)
> >  		return -EINVAL;
> >  
> >  	arg_list.count = 1;
> > 
> 
> hm, maybe.
> 
> This can only happen if acpi_evaluate_integer(MEMORY_GET_BANDWIDTH)
> returned no-error and a bandwidth of zero (I assume).
> 
> Is this a special case which the driver really wanted to handle?  If
> so, why is "0" the only bad value which we're checking for?  Or is this
> all some big brainfart which should be removed?

Sujith,
Please send me a patch to intel_menlo.c that documents the
legal return values from GTHS.

If 0 is illegal, that is fine, but the upstream driver doesn't
check for it properl (I like Rui's 9/11 patch better than the above,
so andrew, you can drop this patch in any case)

thanks,
-Len

ps.  Sujith, shouldn't there be a MAINTAINERS for this driver with your 
name on it?



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