Date: Thu, 18 Oct 2012 02:30:09 +0000 (GMT)
From: MyungJoo Ham <myungjoo.ham@samsung.com>
Subject: Re: [PATCH] PM / OPP: predictable fail results for opp_find* functions
To: Nishanth Menon <nm@ti.com>,
        "linux-pm@vger.kernel.org" <linux-pm@vger.kernel.org>
Cc: =?euc-kr?Q?=B9=DA=B0=E6=B9=CE?= <kyungmin.park@samsung.com>,
        "Rafael J. Wysocki" <rjw@sisk.pl>, Kevin Hilman <khilman@ti.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Reply-to: myungjoo.ham@samsung.com
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> 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@samsung.com>
> Cc: Kyungmin Park <kyungmin.park@samsung.com>
> Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
> Cc: Kevin Hilman <khilman@ti.com>
> Cc: linux-pm@vger.kernel.org
> Cc: linux-kernel@vger.kernel.org
> 
> Signed-off-by: Nishanth Menon <nm@ti.com>

Thanks.


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


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