samsung-galaxybook writes to a int via a u8*

From: Gianni Ceccarelli
Date: Sun Dec 28 2025 - 07:02:51 EST


https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/tree/drivers/platform/x86/samsung-galaxybook.c#n450

`val->intval` is an int (see
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/tree/include/linux/power_supply.h#n228
), so writing to it via a `u8*` produces weird results, for example:

$ cat /sys/class/power_supply/BAT1/charge_control_end_threshold
78497792
$ grep END_THRESHOLD /sys/class/power_supply/BAT1/uevent
POWER_SUPPLY_CHARGE_CONTROL_END_THRESHOLD=-962691840

The least-significant byte of numbers values contains the expected
value:

$ perl -E 'say 78497792 & 0xFF'
0
$ perl -E 'say -962691840 & 0xFF'
0

even after changing the threshold:

# echo 90 >
/sys/class/power_supply/BAT1/charge_control_end_threshold $ cat
/sys/class/power_supply/BAT1/charge_control_end_threshold 78497882
$ grep END_THRESHOLD /sys/class/power_supply/BAT1/uevent
POWER_SUPPLY_CHARGE_CONTROL_END_THRESHOLD=-966918822
$ perl -E 'say 78497882 & 0xFF'
90
$ perl -E 'say -966918822 & 0xFF'
90

I guess the code could be changed to:

u8 byteval;
err = charge_control_end_threshold_acpi_get(galaxybook, &byteval);
if (err)
return err;
val->intval = byteval;

Hope this helps.

--
Dakkar - <Mobilis in mobile>
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