Bug 218767

Summary:	Battery trip point default is design capacity of warning but should be design capacity of low
Product:	ACPI	Reporter:	Matt H (snafu109)
Component:	Power-Battery	Assignee:	acpi_power-battery
Status:	NEW ---
Severity:	normal
Priority:	P3
Hardware:	All
OS:	Linux
Kernel Version:		Subsystem:
Regression:	No	Bisected commit-id:

Description Matt H 2024-04-24 01:19:42 UTC

The default battery trip point is set to design capacity of warning: https://github.com/torvalds/linux/blob/9d1ddab261f3e2af7c384dc02238784ce0cf9f98/drivers/acpi/battery.c#L654

There are two issues:
1. ACPI spec says design capacity of warning should trigger OS notification through the UI. It says nothing about the system doing anything or triggering sleep, so this value should be irrelevant as far as kernel behaviour is concerned.
2. Windows ignores design capacity of warning. If Windows ignores it OEMs will inevitably not test it properly. Source: https://learn.microsoft.com/en-us/windows-hardware/design/component-guidelines/acpi-battery-and-power-subsystem-firmware-implementation

Setting battery trip point to design capacity of low matches ACPI spec and aligns to Windows so is more likely properly tested by OEMs.

Supporting point 2 is this note: https://github.com/torvalds/linux/blob/9d1ddab261f3e2af7c384dc02238784ce0cf9f98/drivers/acpi/battery.c#L509-L510