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[PATCH] iio: core: Fix IIO_VAL_FRACTIONAL_LOG2 for negative values

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  [PATCH] iio: core: Fix IIO_VAL_FRACTIONAL_LOG2 for negative values Nikolaus Schulz <nikolaus.schulz@avionic-design.de> - 2017-03-24 14:00 +0100
    Re: [PATCH] iio: core: Fix IIO_VAL_FRACTIONAL_LOG2 for negative  values Jonathan Cameron <jic23@kernel.org> - 2017-03-25 19:10 +0100

#1608384 — [PATCH] iio: core: Fix IIO_VAL_FRACTIONAL_LOG2 for negative values

Fix formatting of negative values of type IIO_VAL_FRACTIONAL_LOG2 by
switching from do_div(), which can't handle negative numbers, to
div_s64_rem().  Also use shift_right for shifting, which is safe with
negative values.

Signed-off-by: Nikolaus Schulz <nikolaus.schulz@avionic-design.de>
Cc: stable@vger.kernel.org
---
 drivers/iio/industrialio-core.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/drivers/iio/industrialio-core.c b/drivers/iio/industrialio-core.c
index d18ded4..3ff91e0 100644
--- a/drivers/iio/industrialio-core.c
+++ b/drivers/iio/industrialio-core.c
@@ -610,10 +610,9 @@ static ssize_t __iio_format_value(char *buf, size_t len, unsigned int type,
 		tmp0 = (int)div_s64_rem(tmp, 1000000000, &tmp1);
 		return snprintf(buf, len, "%d.%09u", tmp0, abs(tmp1));
 	case IIO_VAL_FRACTIONAL_LOG2:
-		tmp = (s64)vals[0] * 1000000000LL >> vals[1];
-		tmp1 = do_div(tmp, 1000000000LL);
-		tmp0 = tmp;
-		return snprintf(buf, len, "%d.%09u", tmp0, tmp1);
+		tmp = shift_right((s64)vals[0] * 1000000000LL, vals[1]);
+		tmp0 = (int)div_s64_rem(tmp, 1000000000LL, &tmp1);
+		return snprintf(buf, len, "%d.%09u", tmp0, abs(tmp1));
 	case IIO_VAL_INT_MULTIPLE:
 	{
 		int i;
-- 
2.1.4

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#1609199 — Re: [PATCH] iio: core: Fix IIO_VAL_FRACTIONAL_LOG2 for negative values

On 24/03/17 12:41, Nikolaus Schulz wrote:
> Fix formatting of negative values of type IIO_VAL_FRACTIONAL_LOG2 by
> switching from do_div(), which can't handle negative numbers, to
> div_s64_rem().  Also use shift_right for shifting, which is safe with
> negative values.
> 
> Signed-off-by: Nikolaus Schulz <nikolaus.schulz@avionic-design.de>
> Cc: stable@vger.kernel.org
Looks sane to me, but I'd like to give others time to comment on this
just in case there is some odd condition neither of us has thought of!

Give me a poke if we get nothing else for a few weeks.

Jonathan
> ---
>  drivers/iio/industrialio-core.c | 7 +++----
>  1 file changed, 3 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/iio/industrialio-core.c b/drivers/iio/industrialio-core.c
> index d18ded4..3ff91e0 100644
> --- a/drivers/iio/industrialio-core.c
> +++ b/drivers/iio/industrialio-core.c
> @@ -610,10 +610,9 @@ static ssize_t __iio_format_value(char *buf, size_t len, unsigned int type,
>  		tmp0 = (int)div_s64_rem(tmp, 1000000000, &tmp1);
>  		return snprintf(buf, len, "%d.%09u", tmp0, abs(tmp1));
>  	case IIO_VAL_FRACTIONAL_LOG2:
> -		tmp = (s64)vals[0] * 1000000000LL >> vals[1];
> -		tmp1 = do_div(tmp, 1000000000LL);
> -		tmp0 = tmp;
> -		return snprintf(buf, len, "%d.%09u", tmp0, tmp1);
> +		tmp = shift_right((s64)vals[0] * 1000000000LL, vals[1]);
> +		tmp0 = (int)div_s64_rem(tmp, 1000000000LL, &tmp1);
> +		return snprintf(buf, len, "%d.%09u", tmp0, abs(tmp1));
>  	case IIO_VAL_INT_MULTIPLE:
>  	{
>  		int i;
> 

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