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

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Message-ID: <2bf96d78-955a-d995-9a55-04c937b39af5@kernel.org>
Date:	Sun, 26 Jun 2016 17:05:45 +0100
From:	Jonathan Cameron <jic23@...nel.org>
To:	Matt Ranostay <mranostay@...il.com>
Cc:	"Andrew F. Davis" <afd@...com>, Arnd Bergmann <arnd@...db.de>,
	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 12/06/16 07:55, Matt Ranostay wrote:
> 
> Also important to note these warnings are environment related (e.g. room with lot of EMI noise) and unlikely a chip misconfiguration. Unless the tuning capacitor setting is wrong of course
Applied to the togreg branch of iio.git. Initially pushed out as testing
for the autobuilders to play with it.

Thanks,

Jonathan
> 
>> On Jun 11, 2016, at 09:32, Jonathan Cameron <jic23@...nel.org> wrote:
>>
>>> 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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