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

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Date:	Thu, 18 Oct 2012 02:30:09 +0000 (GMT)
From:	MyungJoo Ham <myungjoo.ham@...sung.com>
To:	Nishanth Menon <nm@...com>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>
Cc:	박경민 <kyungmin.park@...sung.com>,
	"Rafael J. Wysocki" <rjw@...k.pl>, Kevin Hilman <khilman@...com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] PM / OPP: predictable fail results for opp_find* functions

> 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);
> 
> Cc: MyungJoo Ham <myungjoo.ham@...sung.com>
> Cc: Kyungmin Park <kyungmin.park@...sung.com>
> Cc: "Rafael J. Wysocki" <rjw@...k.pl>
> Cc: Kevin Hilman <khilman@...com>
> Cc: linux-pm@...r.kernel.org
> Cc: linux-kernel@...r.kernel.org
> 
> Signed-off-by: Nishanth Menon <nm@...com>

Thanks.


Acked-by: MyungJoo Ham <myungjoo.ham@...sung.com>


>