[PATCH 2/3] iio: iio_format_value(): Fix IIO_VAL_FRACTIONAL_LOG2 values between -1.0 and 0.0 - Lars-Peter Clausen

From: Lars-Peter Clausen <lars@metafoo.de>
To: Jonathan Cameron <jic23@kernel.org>
Cc: Peter Meerwald-Stadler <pmeerw@pmeerw.net>,
	linux-iio@vger.kernel.org, Lars-Peter Clausen <lars@metafoo.de>
Subject: [PATCH 2/3] iio: iio_format_value(): Fix IIO_VAL_FRACTIONAL_LOG2 values between -1.0 and 0.0
Date: Tue, 15 Dec 2020 20:17:42 +0100	[thread overview]
Message-ID: <20201215191743.2725-2-lars@metafoo.de> (raw)
In-Reply-To: <20201215191743.2725-1-lars@metafoo.de>

When formatting a value using IIO_VAL_FRACTIONAL_LOG2 and the values is
between -1 and 0 the sign is omitted.

We need the same trick as for IIO_VAL_FRACTIONAL to make sure this gets
formatted correctly.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
---
Found while writing a unit test for this.

Considering nobody complained we probably do not have an driver that will
run into this issue at the moment. So this doesn't need to got to stable.
---
 drivers/iio/industrialio-core.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/iio/industrialio-core.c b/drivers/iio/industrialio-core.c
index d84b74cc544b..4b30c042e5f6 100644
--- a/drivers/iio/industrialio-core.c
+++ b/drivers/iio/industrialio-core.c
@@ -626,7 +626,10 @@ static ssize_t __iio_format_value(char *buf, size_t len, unsigned int type,
 	case IIO_VAL_FRACTIONAL_LOG2:
 		tmp2 = shift_right((s64)vals[0] * 1000000000LL, vals[1]);
 		tmp0 = (int)div_s64_rem(tmp2, 1000000000LL, &tmp1);
-		return scnprintf(buf, len, "%d.%09u", tmp0, abs(tmp1));
+		if (tmp0 == 0 && tmp2 < 0)
+			return snprintf(buf, len, "-0.%09u", abs(tmp1));
+		else
+			return scnprintf(buf, len, "%d.%09u", tmp0, abs(tmp1));
 	case IIO_VAL_INT_MULTIPLE:
 	{
 		int i;
-- 
2.20.1

