[PATCH] hwmon: (w83627ehf) Clamp voltage limits before scaling

[Zhu Jun]

From: zhujun <zhujun2@xxxxxxxxxxxxxxxxxxxx>

in_to_reg() narrows the sysfs value to u32 and multiplies it by 100
before clamping. A large positive voltage limit can consequently be
programmed as zero instead of the maximum; 4294967296 mV reproduces this
on a 64-bit system.

Preserve the input width and clamp to the representable voltage range
before multiplication.

Developed with assistance from OpenAI Codex.

Fixes: cf0676fe42c8 ("[PATCH] w83627ehf: Add voltage inputs 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/hwmon/w83627ehf.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/hwmon/w83627ehf.c b/drivers/hwmon/w83627ehf.c
index 9c08ab662dc6..5c04b9c52b76 100644
--- a/drivers/hwmon/w83627ehf.c
+++ b/drivers/hwmon/w83627ehf.c
@@ -293,8 +293,9 @@ static inline long in_from_reg(u8 reg, u8 nr, const u16 *scale_in)
 	return DIV_ROUND_CLOSEST(reg * scale_in[nr], 100);
 }
 
-static inline u8 in_to_reg(u32 val, u8 nr, const u16 *scale_in)
+static inline u8 in_to_reg(unsigned long val, u8 nr, const u16 *scale_in)
 {
+	val = min(val, 255UL * scale_in[nr] / 100);
 	return clamp_val(DIV_ROUND_CLOSEST(val * 100, scale_in[nr]), 0, 255);
 }
 

base-commit: 7475ea8b58616b33c04afb976cf0fbaad9dd63fb
-- 
2.51.0