linux-kernel - Re: [PATCH v2 1/6] staging:iio:ad2s90: Make read_raw return spi

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Date:   Fri, 2 Nov 2018 10:49:59 -0300
From:   Matheus Tavares <matheus.bernardino@....br>
To:     Jonathan Cameron <jic23@...nel.org>
Cc:     Lars-Peter Clausen <lars@...afoo.de>,
        Michael Hennerich <Michael.Hennerich@...log.com>,
        Hartmut Knaack <knaack.h@....de>,
        Peter Meerwald-Stadler <pmeerw@...erw.net>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-iio@...r.kernel.org, devel@...verdev.osuosl.org,
        linux-kernel@...r.kernel.org, kernel-usp@...glegroups.com
Subject: Re: [PATCH v2 1/6] staging:iio:ad2s90: Make read_raw return
 spi_read's error code


On 10/28/18 1:40 PM, Jonathan Cameron wrote:
> On Fri, 26 Oct 2018 23:00:00 -0300
> Matheus Tavares <matheus.bernardino@....br> wrote:
>
>> Previously, when spi_read returned an error code inside ad2s90_read_raw,
>> the code was ignored and IIO_VAL_INT was returned. This patch makes the
>> function return the error code returned by spi_read when it fails.
>>
>> Signed-off-by: Matheus Tavares <matheus.bernardino@....br>
> Hi Matheus,
>
> One quick process note is that it takes people a while to get around to reviewing
> a series, so whilst it's tempting to very quickly send out a fix the moment
> someone points out something that needs fixing, it is perhaps better to wait
> at least a few days to see if you can pick up a few more reviews before you
> do a V2.
>
> A few comments on this one inline.  I think it can be done 'slightly'
> (and I mean only slightly) nicer than the version you have.  Result is the
> same though.
>
> Thanks,
>
> Jonathan
>
>> ---
>>   drivers/staging/iio/resolver/ad2s90.c | 9 ++++++---
>>   1 file changed, 6 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/staging/iio/resolver/ad2s90.c b/drivers/staging/iio/resolver/ad2s90.c
>> index 59586947a936..11fac9f90148 100644
>> --- a/drivers/staging/iio/resolver/ad2s90.c
>> +++ b/drivers/staging/iio/resolver/ad2s90.c
>> @@ -35,12 +35,15 @@ static int ad2s90_read_raw(struct iio_dev *indio_dev,
>>   	struct ad2s90_state *st = iio_priv(indio_dev);
>>   
>>   	mutex_lock(&st->lock);
>> +
> Unconnected change.  I'm not against the change in principle but please
> group white space tidying up in it's own patch.
>
>>   	ret = spi_read(st->sdev, st->rx, 2);
>> -	if (ret)
>> -		goto error_ret;
>> +	if (ret < 0) {
>> +		mutex_unlock(&st->lock);
>> +		return ret;
> I'd actually prefer to keep the return path the same as before as then
> it is easy (if the function gets more complex in future) to be sure
> that all paths unlock the mutex.


Ok, got it! But then, in patch 5, when we add the switch for 
IIO_CHAN_INFO_SCALE and IIO_CHAN_INFO_RAW, should I keep the goto and 
label inside the switch case? I mean, should it be something like this:


     switch (m) {
     case IIO_CHAN_INFO_SCALE:
         ... // Does not use mutex
     case IIO_CHAN_INFO_RAW:
         mutex_lock(&st->lock);
         ret = spi_read(st->sdev, st->rx, 2);
         if (ret)
             goto error_ret;
         *val = (((u16)(st->rx[0])) << 4) | ((st->rx[1] & 0xF0) >> 4);

error_ret:
         mutex_unlock(&st->lock);

         return ret ? ret : IIO_VAL_INT;
     default:
         break;
     }


Matheus


>> +	}
>> +
>>   	*val = (((u16)(st->rx[0])) << 4) | ((st->rx[1] & 0xF0) >> 4);
>>   
>> -error_ret:
>>   	mutex_unlock(&st->lock);
>>   
>>   	return IIO_VAL_INT;
> The 'standard' if slightly nasty way of doing this is:
>
> 	return ret ? ret : IIO_VAL_INT;
>