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acpi_battery: avoid divide-by-zero when no devices have capacity info

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On laptops with builtin batteries, disconnecting the battery may show up
as a battery without any capacity information. (The theory is that one
is disconnecting the cells but the electronics identifying the battery
are still connected.) As a result, the loop over all batteries in
acpi_battery_get_battinfo results in total_lfcap == 0.

So, just check that total_lfcap is non-zero to avoid a division by zero
(triggerable by sysctl hw.acpi.battery).

Reported by:	Stefano Marinelli
Tested by:	Stefano Marinelli
Reviewed by:	emaste
Differential Revision: https://reviews.freebsd.org/D44818

(cherry picked from commit 2e850b832f)
(cherry picked from commit 788987e034)
This commit is contained in:
Josef 'Jeff' Sipek 2024-04-16 19:01:28 -04:00 committed by Ed Maste
parent e03c9c311e
commit 1a4e512adb
1 changed files with 8 additions and 1 deletions
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9
sys/dev/acpica/acpi_battery.c
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@ -266,7 +266,14 @@ acpi_battery_get_battinfo(device_t dev, struct acpi_battinfo *battinfo)
*/
if (valid_units > 0) {
if (dev == NULL) {
battinfo->cap = (total_cap * 100) / total_lfcap;
/*
* Avoid division by zero if none of the batteries had valid
* capacity info.
*/
if (total_lfcap > 0)
battinfo->cap = (total_cap * 100) / total_lfcap;
else
battinfo->cap = 0;
battinfo->min = total_min;
battinfo->state = batt_stat;
battinfo->rate = valid_rate;