linux-kernel - Re: [PATCH] iio: as3935: improve error reporting in as3935_event

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Date:	Sat, 11 Jun 2016 17:32:04 +0100
From:	Jonathan Cameron <jic23@...nel.org>
To:	"Andrew F. Davis" <afd@...com>, Arnd Bergmann <arnd@...db.de>
Cc:	Hartmut Knaack <knaack.h@....de>,
	Lars-Peter Clausen <lars@...afoo.de>,
	Peter Meerwald-Stadler <pmeerw@...erw.net>,
	Mark Brown <broonie@...nel.org>,
	Javier Martinez Canillas <javier@....samsung.com>,
	linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] iio: as3935: improve error reporting in as3935_event_work

On 31/05/16 15:53, Andrew F. Davis wrote:
> On 05/30/2016 09:52 AM, Arnd Bergmann wrote:
>> gcc warns about a potentially uninitialized variable use
>> in as3935_event_work:
>>
>> drivers/iio/proximity/as3935.c: In function ‘as3935_event_work’:
>> drivers/iio/proximity/as3935.c:231:6: error: ‘val’ may be used uninitialized in this function [-Werror=maybe-uninitialized]
>>
>> This case specifically happens when spi_w8r8() fails with a
>> negative return code. We check all other users of this function
>> except this one.
>>
>> As the error is rather unlikely to happen after the device
>> has already been initialized, this just adds a dev_warn().
>> Another warning already existst in the same function, but is
> 
>                             ^^ typo
> 
>> missing a trailing '\n' character, so I'm fixing that too.
>>
>> Signed-off-by: Arnd Bergmann <arnd@...db.de>
>> ---
>>  drivers/iio/proximity/as3935.c | 10 ++++++++--
>>  1 file changed, 8 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/iio/proximity/as3935.c b/drivers/iio/proximity/as3935.c
>> index f4d29d5dbd5f..b49e3ab5730a 100644
>> --- a/drivers/iio/proximity/as3935.c
>> +++ b/drivers/iio/proximity/as3935.c
>> @@ -224,10 +224,16 @@ static void as3935_event_work(struct work_struct *work)
>>  {
>>  	struct as3935_state *st;
>>  	int val;
>> +	int ret;
>>  
>>  	st = container_of(work, struct as3935_state, work.work);
>>  
>> -	as3935_read(st, AS3935_INT, &val);
>> +	ret = as3935_read(st, AS3935_INT, &val);
>> +	if (ret) {
>> +		dev_warn(&st->spi->dev, "read error\n");
> 
> Maybe I'm misunderstanding the commit message, why does this error not
> use dev_err()? A read error here would be rather serious, it might even
> be worth it to return a code and fail through the caller too.
They are unusual and typically result in momentary corruption.  Hmm.
As this is in a work function, there is no easy way of actually
passing the error upstream..  dev_err is a little brutal so perhaps
this is the best option...
> 
>> +		return;
>> +	}
>> +
>>  	val &= AS3935_INT_MASK;
>>  
>>  	switch (val) {
>> @@ -235,7 +241,7 @@ static void as3935_event_work(struct work_struct *work)
>>  		iio_trigger_poll(st->trig);
>>  		break;
>>  	case AS3935_NOISE_INT:
>> -		dev_warn(&st->spi->dev, "noise level is too high");
>> +		dev_warn(&st->spi->dev, "noise level is too high\n");
>>  		break;
>>  	}
>>  }
>>
> --
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