Re: [PATCH v2] iio: core: Fix IIO_VAL_FRACTIONAL calculation for negative values
From: Jonathan Cameron <jic23@kernel.org>
Date: 2020-08-29 15:19:08
Also in:
linux-iio, lkml
On Wed, 26 Aug 2020 11:14:36 -0700 Anand Ashok Dumbre [off-list ref] wrote:
Fixes IIO_VAL_FRACTIONAL for case when the result is negative and exponent is 0. example: if the result is -0.75, tmp0 will be 0 and tmp1 = 75 This causes the output to lose sign because of %d in snprintf which works for tmp0 <= -1. Signed-off-by: Anand Ashok Dumbre <redacted>
Looks good. Just one last thing. Is this actually hit in an existing driver? I'm just wondering how far back we need to push it in stable etc. Thanks, Jonathan
quoted hunk ↗ jump to hunk
--- changes since v1: Changed -%d to -0 to make the fix clearer. Removed the email footer. Updated the commit description with an example -- drivers/iio/industrialio-core.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-)diff --git a/drivers/iio/industrialio-core.c b/drivers/iio/industrialio-core.c index cdcd16f1..a239fa2 100644 --- a/drivers/iio/industrialio-core.c +++ b/drivers/iio/industrialio-core.c@@ -592,6 +592,7 @@ static ssize_t __iio_format_value(char *buf, size_t len, unsigned int type, { unsigned long long tmp; int tmp0, tmp1; + s64 tmp2; bool scale_db = false; switch (type) {@@ -614,10 +615,13 @@ static ssize_t __iio_format_value(char *buf, size_t len, unsigned int type, else return scnprintf(buf, len, "%d.%09u", vals[0], vals[1]); case IIO_VAL_FRACTIONAL: - tmp = div_s64((s64)vals[0] * 1000000000LL, vals[1]); + tmp2 = div_s64((s64)vals[0] * 1000000000LL, vals[1]); tmp1 = vals[1]; tmp0 = (int)div_s64_rem(tmp, 1000000000, &tmp1); - return scnprintf(buf, len, "%d.%09u", tmp0, abs(tmp1)); + if ((tmp2 < 0) && (tmp0 == 0)) + return snprintf(buf, len, "-0.%09u", abs(tmp1)); + else + return snprintf(buf, len, "%d.%09u", tmp0, abs(tmp1)); case IIO_VAL_FRACTIONAL_LOG2: tmp = shift_right((s64)vals[0] * 1000000000LL, vals[1]); tmp0 = (int)div_s64_rem(tmp, 1000000000LL, &tmp1);
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