linux-kernel - Re: [PATCH v2 1/3] pwm: Add pwm_cansleep() as exported API to users

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Message-ID: <510659A3.7070906@epfl.ch>
Date:	Mon, 28 Jan 2013 11:57:39 +0100
From:	Florian Vaussard <florian.vaussard@...l.ch>
To:	Thierry Reding <thierry.reding@...onic-design.de>
CC:	Peter Ujfalusi <peter.ujfalusi@...com>,
	Bryan Wu <cooloney@...il.com>,
	Richard Purdie <rpurdie@...ys.net>, linux-leds@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/3] pwm: Add pwm_cansleep() as exported API to users

Le 28/01/2013 10:57, Thierry Reding a écrit :
> On Mon, Jan 28, 2013 at 10:36:07AM +0100, Florian Vaussard wrote:
>> Hello,
>>
>> Le 28/01/2013 09:45, Peter Ujfalusi a écrit :
>>> hi Thierry,
>>>
>>> On 01/26/2013 06:40 AM, Thierry Reding wrote:
> [...]
>>>>> +{
>>>>> +	return pwm->chip->can_sleep;
>>>>> +}
>>>>> +EXPORT_SYMBOL_GPL(pwm_cansleep);
>>>>
>>>> Would it make sense to check for NULL pointers here? I guess that
>>>> passing NULL into the function could be considered a programming error
>>>> and an oops would be okay, but in that case there's no point in making
>>>> the function return an int. Also see my next comment.
>>>
>>> While it is unlikely to happen it is better to be safe, something like this
>>> will do:
>>>
>>> return pwm ? pwm->chip->can_sleep : 0;
>>>
>>
>> Ok. And what about:
>>
>> BUG_ON(pwm == NULL);
>> return pwm->chip->can_sleep;
>
> I don't think we need that. In case pwm == NULL, dereferencing it will
> oops anyway. So either we make it safe and return an error code, or we
> let it oops without explicit BUG_ON().
>

Calling this function with a NULL pointer is a programming error, so there
is no error codes for such errors. I propose to return bool, and let it
oops if such case happens.

Regards,

Florian
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