linux-kernel - Re: [PATCH 2/2] iio: inkern: put the IIO device when mem alloc gets failed

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Date:	Mon, 17 Sep 2012 20:58:14 +0100
From:	Jonathan Cameron <jic23@...nel.org>
To:	"Kim, Milo" <Milo.Kim@...com>
CC:	Lars-Peter Clausen <lars@...afoo.de>,
	Jonathan Cameron <jic23@....ac.uk>,
	"linux-iio@...r.kernel.org" <linux-iio@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] iio: inkern: put the IIO device when mem alloc gets
 failed

On 09/17/2012 10:57 AM, Kim, Milo wrote:
>>>  drivers/iio/inkern.c |    5 ++++-
>>>  1 file changed, 4 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/iio/inkern.c b/drivers/iio/inkern.c
>>> index 13748c0..aff034b 100644
>>> --- a/drivers/iio/inkern.c
>>> +++ b/drivers/iio/inkern.c
>>> @@ -132,7 +132,7 @@ struct iio_channel *iio_channel_get(const char
>> *name, const char *channel_name)
>>>
>>>  	channel = kzalloc(sizeof(*channel), GFP_KERNEL);
>>>  	if (channel == NULL)
>>> -		return ERR_PTR(-ENOMEM);
>>> +		goto error_no_mem;
>>>
>>>  	channel->indio_dev = c->indio_dev;
>>>
>>> @@ -151,6 +151,9 @@ error_no_chan:
>>>  	iio_device_put(c->indio_dev);
>>>  	kfree(channel);
>>>  	return ERR_PTR(-EINVAL);
>>> +error_no_mem:
>>> +	iio_device_put(c->indio_dev);
>>> +	return ERR_PTR(-ENOMEM);
>>>  }
>>>  EXPORT_SYMBOL_GPL(iio_channel_get);
>>>
>>
>> If you do it that way, you don't really need the goto, something like
>>
>> error_no_chan:
>>   	kfree(channel);
>> error_no_mem:
>> 	iio_device_put(c->indio_dev);
>> 	return ret
>>
>> would be better in my opinion. With ret being initialized in the if
>> branch
>> before the goto.
> 
> Thanks for your opinion. I was hesitating before sending ;) 
> 
> The reason why this patch need separate goto statement is as below.
>  
> There are two different types when requesting the channel.
> One is a pointer of iio_channel, the other is the error.
> So return type will be two - allocated iio_channel and integer.
> For simplicity, I would use just one return variable when it runs successfully.
> In error cases, do return as explicit name such like ERR_PTR() rather than
> saving into local integer.
> 
I can see your point, but Lars-Peter's way is the more commonly used approach
so lets go with the ancient arguement of making it look like what those
reading the code expect to see ;)

> Just my two cents.
> But your code has better readability.
> 
> Thank you.
> 
> Best Regards,
> Milo
> 
> 
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