linux-kernel - Re: [PATCH] max8925_power: Use "IS_ENABLED(CONFIG

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Date:	Mon, 27 Jan 2014 03:46:28 +0400
From:	Dmitry Eremin-Solenikov <dbaryshkov@...il.com>
To:	Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc:	Tomasz Figa <tomasz.figa@...il.com>,
	Manish Badarkhe <badarkhe.manish@...il.com>,
	"linux-samsung-soc@...r.kernel.org" 
	<linux-samsung-soc@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	David Woodhouse <dwmw2@...radead.org>
Subject: Re: [PATCH] max8925_power: Use "IS_ENABLED(CONFIG_OF)" for DT code.

On Mon, Jan 27, 2014 at 3:14 AM, Dmitry Torokhov
<dmitry.torokhov@...il.com> wrote:
> On Mon, Jan 27, 2014 at 02:31:59AM +0400, Dmitry Eremin-Solenikov wrote:
>> On Mon, Jan 27, 2014 at 1:49 AM, Tomasz Figa <tomasz.figa@...il.com> wrote:
>> > On 26.01.2014 22:45, Dmitry Torokhov wrote:
>> >>
>> >> On Sun, Jan 26, 2014 at 07:31:50PM +0530, Manish Badarkhe wrote:
>> >>>
>> >>> Hi Tomasz,
>> >>>
>> >>> Thank you for your review comments.
>> >>>
>> >>> On Sun, Jan 26, 2014 at 6:52 PM, Tomasz Figa <tomasz.figa@...il.com>
>> >>> wrote:
>> >>>>
>> >>>>
>> >>>> Hi Manish,
>> >>>>
>> >>>>
>> >>>> On 26.01.2014 08:15, Manish Badarkhe wrote:
>> >>>>>
>> >>>>>
>> >>>>> Instead of "#if define CONFIG_OF" use "IS_ENABLED(CONFIG_OF)"
>> >>>>> option for DT code to avoid if-deffery in code.
>> >>>>>
>> >>>>> Signed-off-by: Manish Badarkhe <badarkhe.manish@...il.com>
>> >>>>> ---
>> >>>>> :100644 100644 b4513f2... d353fbc... M  drivers/power/max8925_power.c
>> >>>>>    drivers/power/max8925_power.c |   14 +++++---------
>> >>>>>    1 file changed, 5 insertions(+), 9 deletions(-)
>> >>>>>
>> >>>>> diff --git a/drivers/power/max8925_power.c
>> >>>>> b/drivers/power/max8925_power.c
>> >>>>> index b4513f2..d353fbc 100644
>> >>>>> --- a/drivers/power/max8925_power.c
>> >>>>> +++ b/drivers/power/max8925_power.c
>> >>>>> @@ -427,7 +427,6 @@ static int max8925_deinit_charger(struct
>> >>>>> max8925_power_info *info)
>> >>>>>          return 0;
>> >>>>>    }
>> >>>>>
>> >>>>> -#ifdef CONFIG_OF
>> >>>>>    static struct max8925_power_pdata *
>> >>>>>    max8925_power_dt_init(struct platform_device *pdev)
>> >>>>>    {
>> >>>>> @@ -468,13 +467,6 @@ max8925_power_dt_init(struct platform_device
>> >>>>> *pdev)
>> >>>>>
>> >>>>>          return pdata;
>> >>>>>    }
>> >>>>> -#else
>> >>>>> -static struct max8925_power_pdata *
>> >>>>> -max8925_power_dt_init(struct platform_device *pdev)
>> >>>>> -{
>> >>>>> -       return pdev->dev.platform_data;
>> >>>>> -}
>> >>>>> -#endif
>> >>>>>
>> >>>>>    static int max8925_power_probe(struct platform_device *pdev)
>> >>>>>    {
>> >>>>> @@ -483,7 +475,11 @@ static int max8925_power_probe(struct
>> >>>>> platform_device *pdev)
>> >>>>>          struct max8925_power_info *info;
>> >>>>>          int ret;
>> >>>>>
>> >>>>> -       pdata = max8925_power_dt_init(pdev);
>> >>>>> +       if (IS_ENABLED(CONFIG_OF))
>> >>>>> +               pdata = max8925_power_dt_init(pdev);
>> >>>>> +       else
>> >>>>> +               pdata = pdev->dev.platform_data;
>> >>>>> +
>> >>>>
>> >>>>
>> >>>>
>> >>>> This does not look much better than before this patch. Instead of
>> >>>> "if-deffery" outside function bodies you are adding "iffery" (if there is
>> >>>> such a word) inside a function.
>> >>>> What about adding
>> >>>>
>> >>>>          if (!IS_ENABLED(CONFIG_OF))
>> >>>>                  return pdev->dev.platform_data;
>> >>>>
>> >>>> on top of max8925_power_dt_init() instead or maybe also renaming this
>> >>>> function to max8925_get_pdata()?
>> >>>
>> >>>
>> >>> Okay, I will rename function "max8925_power_dt_init()" to
>> >>> "max8925_get_pdata()".
>> >>> As you suggested, in the body of this function  will add a logic to
>> >>> retrieve  data in case
>> >>> of DT and non-DT platforms.
>> >>
>> >>
>> >> Should we not always favor platform-supplied data regardless of
>> >> CONFIG_OF state and fall back to DT (firmware) supplied data if platform
>> >> data is absent? This way one can tweak kernel behavior without needing
>> >> to change firmware.
>> >
>> >
>> > I guess we should, but apparently this was not the original behavior before
>> > this patch, so I'm not sure if we should be squashing such semantic change
>> > with this simple refactor.
>>
>> Hmm. Judging from the code, max8925_power_dt_init() function follows exactly
>> opposite strategy - it uses platform_data if of_node is not populated/available.
>> So (if dt_init will compile with CONFIG_OF disabled) one can always
>> use _dt_init()
>> function to retrieve pdata.
>
> Right, and I question whether this is good behavior or if it should be
> corrected.

I'd say, correct it.

-- 
With best wishes
Dmitry
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