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iio:core: fix IIO_VAL_FRACTIONAL sign handling 

7985e7c100 ("iio: Introduce a new fractional value type") introduced a
new IIO_VAL_FRACTIONAL value type meant to represent rational type numbers
expressed by a numerator and denominator combination.

Formating of IIO_VAL_FRACTIONAL values relies upon do_div() usage. This
fails handling negative values properly since parameters are reevaluated
as unsigned values.
Fix this by using div_s64_rem() instead. Computed integer part will carry
properly signed value. Formatted fractional part will always be positive.

Fixes: 7985e7c100 ("iio: Introduce a new fractional value type")
Signed-off-by: Gregor Boirie <gregor.boirie@parrot.com>
Reviewed-by: Lars-Peter Clausen <lars@metafoo.de>
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
This commit is contained in:
Gregor Boirie 2016-09-02 20:27:46 +02:00 committed by Jonathan Cameron
parent 5dba4b14ba
commit 171c009183
1 changed files with 2 additions and 3 deletions
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5
drivers/iio/industrialio-core.c
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@ -613,9 +613,8 @@ ssize_t iio_format_value(char *buf, unsigned int type, int size, int *vals)
return sprintf(buf, "%d.%09u\n", vals[0], vals[1]);
case IIO_VAL_FRACTIONAL:
tmp = div_s64((s64)vals[0] * 1000000000LL, vals[1]);
vals[1] = do_div(tmp, 1000000000LL);
vals[0] = tmp;
return sprintf(buf, "%d.%09u\n", vals[0], vals[1]);
vals[0] = (int)div_s64_rem(tmp, 1000000000, &vals[1]);
return sprintf(buf, "%d.%09u\n", vals[0], abs(vals[1]));
case IIO_VAL_FRACTIONAL_LOG2:
tmp = (s64)vals[0] * 1000000000LL >> vals[1];
vals[1] = do_div(tmp, 1000000000LL);