[PATCH] iio: temperature: mcp9600: Bound thresholds before scaling

[PATCH] iio: temperature: mcp9600: Bound thresholds before scaling

[Zhu Jun]

From: zhujun <zhujun2@cmss.chinamobile.com>

mcp9600_write_thresh() multiplies the integer part by 1000000 before
clamping to the supported temperature range. The multiplication can
overflow int, so a request such as 3000 degrees can select the lower
threshold instead of the upper threshold.

Clamp the integer part to the hot-junction range before scaling. Keep
the existing final clamp for fractional values and the narrower cold-
junction range.

Fixes: dea750f8015b ("iio: temperature: mcp9600: add threshold events support")
---
Validation: x86-64 and i386 driver objects built with W=1.
Source-extracted boundary tests passed on 32-bit and 64-bit;
the corresponding test fails on the base revision. I/O is mocked.
No physical sensor hardware or booted-kernel test was available.
OpenAI Codex assisted analysis, code, tests and changelog drafting.
The human submitter must review and add their Signed-off-by.

 drivers/iio/temperature/mcp9600.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/iio/temperature/mcp9600.c b/drivers/iio/temperature/mcp9600.c
index b0ff0c7b4891..51ae622d41f7 100644
--- a/drivers/iio/temperature/mcp9600.c
+++ b/drivers/iio/temperature/mcp9600.c
@@ -326,6 +326,8 @@ static int mcp9600_write_thresh(struct iio_dev *indio_dev,
 	i = mcp9600_get_alert_index(chan->channel2, dir);
 	switch (info) {
 	case IIO_EV_INFO_VALUE:
+		val = clamp_val(val, MCP9600_MIN_TEMP_HOT_JUNCTION_MICRO / 1000000,
+				MCP9600_MAX_TEMP_HOT_JUNCTION_MICRO / 1000000);
 		/* Scale value to include decimal part into calculations */
 		s_val = (val < 0) ? ((val * 1000000) - val2) :
 				    ((val * 1000000) + val2);

base-commit: 7475ea8b58616b33c04afb976cf0fbaad9dd63fb
-- 
2.51.0

Re: [PATCH] iio: temperature: mcp9600: Bound thresholds before scaling

[Joshua Crofts]

On Mon,  9 Nov 2026 17:35:17 +0800
Zhu Jun <zhujun2@cmss.chinamobile.com> wrote:

> From: zhujun <zhujun2@cmss.chinamobile.com>
> 
> mcp9600_write_thresh() multiplies the integer part by 1000000 before
> clamping to the supported temperature range. The multiplication can
> overflow int, so a request such as 3000 degrees can select the lower
> threshold instead of the upper threshold.
> 
> Clamp the integer part to the hot-junction range before scaling. Keep
> the existing final clamp for fractional values and the narrower cold-
> junction range.
> 
> Fixes: dea750f8015b ("iio: temperature: mcp9600: add threshold events support")

You're missing a Signed-off-by tag. Without it, your patch cannot be accepted.

-- 
Kind regards,
Joshua Crofts