Re: [PATCH v3] HID: wacom: validate battery range before scaling

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential
issue to consider:
- [Medium] HID: wacom: out-of-range battery values dropped in
  wacom_wac_event()
--

commit d917c200b45c05631d5073d9e5d68f13f31acf
Author: Aldo Ariel Panzardo <qwe.aldo@gmail.com>

HID: wacom: validate battery range before scaling

This commit moves battery percentage scaling into a helper that checks for
a non-positive logical range, subtracts the logical minimum, and clamps the
computed percentage to [0, 100].

> diff --git a/drivers/hid/wacom_wac.c b/drivers/hid/wacom_wac.c
> index 361738bb87253..36bab07a72dba 100644
> --- a/drivers/hid/wacom_wac.c
> +++ b/drivers/hid/wacom_wac.c
> @@ -1960,6 +1960,16 @@ static void wacom_wac_battery_usage_mapping(struct hid_device *hdev,
>  	return;
>  }
>  
> +static __s32 wacom_wac_battery_percentage(struct hid_field *field, __s32 value)
> +{
> +	__s32 range = field->logical_maximum - field->logical_minimum;
> +
> +	if (range <= 0)
> +		return 0;
> +
> +	return clamp_val((value - field->logical_minimum) * 100 / range, 0, 100);
> +}

[Severity: Medium]
Can an out-of-range battery reading ever reach this clamp_val()?

wacom_wac_battery_percentage() is only called from wacom_wac_battery_event(),
whose sole caller wacom_wac_event() drops any value outside the logical
limits before checking WACOM_BATTERY_USAGE():

drivers/hid/wacom_wac.c:wacom_wac_event() {
    ...
	if (value > field->logical_maximum || value < field->logical_minimum)
		return;

	/* usage tests must precede field tests */
	if (WACOM_BATTERY_USAGE(usage))
		wacom_wac_battery_event(hdev, field, usage, value);
    ...
}

As a result, battery reports outside [field->logical_minimum,
field->logical_maximum] are still discarded in wacom_wac_event() without
setting WACOM_QUIRK_BATTERY or updating battery_capacity, and value is
already within bounds whenever wacom_wac_battery_percentage() runs.

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20261106213526.3393779-1-qwe.aldo@gmail.com?part=1