linux-kernel - Re: [PATCH] PM / OPP: predictable fail results for opp

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Date:	Fri, 19 Oct 2012 01:18:34 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Nishanth Menon <nm@...com>
Cc:	Kevin Hilman <khilman@...prootsystems.com>,
	linux-pm@...r.kernel.org, MyungJoo Ham <myungjoo.ham@...sung.com>,
	Kyungmin Park <kyungmin.park@...sung.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] PM / OPP: predictable fail results for opp_find* functions

On Wednesday 17 of October 2012 15:14:22 Kevin Hilman wrote:
> Nishanth Menon <nm@...com> writes:
> 
> > Currently the opp_find* functions return -ENODEV when:
> > a) it cant find a device (e.g. request for an OPP search on device
> >    which was not registered)
> > b) When it cant find a match for the search strategy used
> >
> > This makes life a little in-efficient for users such as devfreq
> > to make reasonable judgement before switching search strategies.
> >
> > So, standardize the return results as following:
> >  -EINVAL for bad pointer parameters
> >  -ENODEV when device cannot be found
> >  -ERANGE when search fails
> >
> > This has the following benefit for devfreq implementation:
> >
> > Current code:
> > opp = opp_find_freq_floor(dev, freq);
> > /* Following search triggers even for un-registered device */
> > if (opp == ERR_PTR(-ENODEV))
> > 	opp = opp_find_freq_ceil(dev, freq);
> >
> > Vs (after this change):
> > opp = opp_find_freq_floor(dev, freq);
> > /* Will only be triggered if search logic fails: intended usage */
> > if (opp == ERR_PTR(-ERANGE))
> > 	opp = opp_find_freq_ceil(dev, freq);
> 
> I think the idea is fine but would prefer to see the benefits summarized
> in words, rather than code.
> 
> Also, the changelog should describe that the patch not only changes the
> meaning of return values, but also converts devfreq to use the new
> values.
> 
> Otherwise, implementation looks fine.
> 
> Reviewed-by: Kevin Hilman <khilman@...com>

Can you please update the patch as requested by Kevin?

Thanks,
Rafael


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