2023-10-13 13:24:29

by marius.cristea

Subject: [PATCH v2] iio: adc: MCP3564: fix warn: unsigned '__x' is never less than zero.

From: Marius Cristea <[email protected]>

The patch 33ec3e5fc1ea: "iio: adc: adding support for MCP3564 ADC"
leads to the following Smatch static checker warning:

smatch warnings:
drivers/iio/adc/mcp3564.c:1105 mcp3564_fill_scale_tbls() warn: unsigned '__x' is never less than zero.

vim +/__x +1105 drivers/iio/adc/mcp3564.c

1094
1095 static void mcp3564_fill_scale_tbls(struct mcp3564_state *adc)
1096 {
.....
1103 for (i = 0; i < MCP3564_MAX_PGA; i++) {
1104 ref = adc->vref_mv;
> 1105 tmp1 = shift_right((u64)ref * NANO, pow);
1106 div_u64_rem(tmp1, NANO, &tmp0);
1107
.....
1113 }

Reported-by: kernel test robot <[email protected]>
Closes: https://lore.kernel.org/oe-kbuild-all/[email protected]/
Fixes: 33ec3e5fc1ea (iio: adc: adding support for MCP3564 ADC)
Signed-off-by: Marius Cristea <[email protected]>
---
drivers/iio/adc/mcp3564.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/iio/adc/mcp3564.c b/drivers/iio/adc/mcp3564.c
index 9ede1a5d5d7b..e3f1de5fcc5a 100644
--- a/drivers/iio/adc/mcp3564.c
+++ b/drivers/iio/adc/mcp3564.c
@@ -1102,7 +1102,7 @@ static void mcp3564_fill_scale_tbls(struct mcp3564_state *adc)

for (i = 0; i < MCP3564_MAX_PGA; i++) {
ref = adc->vref_mv;
- tmp1 = shift_right((u64)ref * NANO, pow);
+ tmp1 = ((u64)ref * NANO) >> pow;
div_u64_rem(tmp1, NANO, &tmp0);

tmp1 = tmp1 * mcp3564_hwgain_frac[(2 * i) + 1];

base-commit: 5e99f692d4e32e3250ab18d511894ca797407aec
--
2.34.1

2023-10-14 16:17:58

by Jonathan Cameron

Subject: Re: [PATCH v2] iio: adc: MCP3564: fix warn: unsigned '__x' is never less than zero.

On Fri, 13 Oct 2023 16:23:33 +0300
<[email protected]> wrote:

> From: Marius Cristea <[email protected]>
>
> The patch 33ec3e5fc1ea: "iio: adc: adding support for MCP3564 ADC"
> leads to the following Smatch static checker warning:
>
> smatch warnings:
> drivers/iio/adc/mcp3564.c:1105 mcp3564_fill_scale_tbls() warn: unsigned '__x' is never less than zero.
>
> vim +/__x +1105 drivers/iio/adc/mcp3564.c
>
> 1094
> 1095 static void mcp3564_fill_scale_tbls(struct mcp3564_state *adc)
> 1096 {
> .....
> 1103 for (i = 0; i < MCP3564_MAX_PGA; i++) {
> 1104 ref = adc->vref_mv;
> > 1105 tmp1 = shift_right((u64)ref * NANO, pow);
> 1106 div_u64_rem(tmp1, NANO, &tmp0);
> 1107
> .....
> 1113 }
>
> Reported-by: kernel test robot <[email protected]>
> Closes: https://lore.kernel.org/oe-kbuild-all/[email protected]/
> Fixes: 33ec3e5fc1ea (iio: adc: adding support for MCP3564 ADC)
> Signed-off-by: Marius Cristea <[email protected]>
Applied to the togreg branch of iio.git and pushed out as testing briefly
for 0-day to take a look.

Thanks,

Jonathan

> ---
> drivers/iio/adc/mcp3564.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/iio/adc/mcp3564.c b/drivers/iio/adc/mcp3564.c
> index 9ede1a5d5d7b..e3f1de5fcc5a 100644
> --- a/drivers/iio/adc/mcp3564.c
> +++ b/drivers/iio/adc/mcp3564.c
> @@ -1102,7 +1102,7 @@ static void mcp3564_fill_scale_tbls(struct mcp3564_state *adc)
>
> for (i = 0; i < MCP3564_MAX_PGA; i++) {
> ref = adc->vref_mv;
> - tmp1 = shift_right((u64)ref * NANO, pow);
> + tmp1 = ((u64)ref * NANO) >> pow;
> div_u64_rem(tmp1, NANO, &tmp0);
>
> tmp1 = tmp1 * mcp3564_hwgain_frac[(2 * i) + 1];
>
> base-commit: 5e99f692d4e32e3250ab18d511894ca797407aec