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SubjectRe: static analysis bug report in drivers/staging/iio/dac/ad5380.c
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On 8/15/19 12:21 PM, Colin Ian King wrote:
> Hi,
>
> Static analysis with Coverity Scan has detected a potential assignment
> bug in ad5380.c:
>
> 217 case IIO_CHAN_INFO_CALIBBIAS:
> 218 ret = regmap_read(st->regmap,
> AD5380_REG_OFFSET(chan->address),
> 219 val);
> 220 if (ret)
> 221 return ret;
> 222 *val >>= chan->scan_type.shift;
>
> CID 43178 (#1 of 1): Unused value (UNUSED_VALUE)assigned_pointer:
> Assigning value from val - (1 << chan->scan_type.realbits) / 2 to val
> here, but that stored value is not used.
>
> 223 val -= (1 << chan->scan_type.realbits) / 2;
> 224 return IIO_VAL_INT;
>
> val is a pointer and so updating it before a return is probably not the
> intention. I suspect the intention was probably:
>
> *val -= (1 << chan->scan_type.realbits) / 2;
>
> However, I'm not confident about this as the following case has:
>
> 225 case IIO_CHAN_INFO_SCALE:
> 226 *val = 2 * st->vref;
> 227 *val2 = chan->scan_type.realbits;
> 228 return IIO_VAL_FRACTIONAL_LOG2;
>
> which may imply the update maybe to *val2 instead, e.g.:
>
> *val2 -= (1 << chan->scan_type.realbits) / 2;
>
> Any ideas?

Updating changing val to *val is the right fix in this case.

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