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

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Date:	Mon, 27 Jan 2014 02:31:59 +0400
From:	Dmitry Eremin-Solenikov <dbaryshkov@...il.com>
To:	Tomasz Figa <tomasz.figa@...il.com>
Cc:	Dmitry Torokhov <dmitry.torokhov@...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 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.

-- 
With best wishes
Dmitry
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