From: Gianni Ceccarelli <dakkar@thenautilus.net>
To: Joshua Grisham <josh@joshuagrisham.com>
Cc: platform-driver-x86@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: samsung-galaxybook writes to a int via a u8*
Date: Sun, 28 Dec 2025 11:55:56 +0000 [thread overview]
Message-ID: <20251228115556.14362d66@thenautilus.net> (raw)
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>
GPG public key fingerprint = A071 E618 DD2C 5901 9574
6FE2 40EA 9883 7519 3F88
key id = 0x75193F88
next reply other threads:[~2025-12-28 12:02 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-12-28 11:55 Gianni Ceccarelli [this message]
2025-12-28 20:16 ` samsung-galaxybook writes to a int via a u8* Armin Wolf
2025-12-28 21:06 ` Gianni Ceccarelli
2025-12-28 21:50 ` Armin Wolf
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