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

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Message-ID: <20140126231452.GE18840@core.coreip.homeip.net>
Date:	Sun, 26 Jan 2014 15:14:52 -0800
From:	Dmitry Torokhov <dmitry.torokhov@...il.com>
To:	Dmitry Eremin-Solenikov <dbaryshkov@...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 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.

Thanks.

-- 
Dmitry
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