kern/173414: ACPI battery time incorrect

[J B]

The following reply was made to PR kern/173414; it has been noted by GNATS.

From: J B <jb.1234abcd at gmail.com>
To: bug-followup at FreeBSD.org, jb.1234abcd at gmail.com
Cc:  
Subject: Re: kern/173414: ACPI battery time incorrect
Date: Tue, 6 Nov 2012 10:07:47 +0100

 $ sysctl -d hw.acpi.battery.time
 hw.acpi.battery.time: remaining time in minutes
 
 Why is it impossible or improper to compute and show battery's remaining
 time ? Because the machine is on on-line power supply ?
 
 The battery's state, that is, its remaining time, is still valid and of
 interest to user at any machine state (load, etc), regardless of power supply
 being on-line or off-line.
 
 I want to know WHAT IF, at any time (without or with consideration of current
 machine state (load, etc) in the computation of battery remaining time),
 I disconnected the on-line power supply, could I expect to happen to my
 machine with regard to expected length-of-time availability of battery power
 supply.
 
 If you think that the battery's "percent capacity remaining" is enough, then
 you are mistaken.
 hw.acpi.battery.life: percent capacity remaining
 
 The battery's "percent capacity remaining" is misleading because its max level
 is degrading over time (the 100% of a new battery is not the same 100% after
 a year or so of random discharging and charging). They just do not tell me
 how much estimated run time I would have as I explained above.
 
 This is what Linux shows about my battery state:
 
 $ cat /proc/acpi/battery/BAT0/info
 present:                 yes
 design capacity:         56160 mWh
 last full capacity:      38720 mWh
 battery technology:      rechargeable
 design voltage:          10800 mV
 design capacity warning: 1936 mWh
 design capacity low:     200 mWh
 capacity granularity 1:  1 mWh
 capacity granularity 2:  1 mWh
 model number:            COMPATIBLE
 serial number:            2413
 battery type:            LION
 OEM info:                BATSZ
 
 $ cat /proc/acpi/battery/BAT0/state
 present:                 yes
 capacity state:          ok
 charging state:          charged
 present rate:            0 mW
 remaining capacity:      38720 mWh
 present voltage:         12405 mV
 
 These are the original and degraded capacity values of 100% I am talking
 about:
 ...
 design capacity:         56160 mWh
 last full capacity:      38720 mWh
 ...
 remaining capacity:      38720 mWh
 ...
 
 So, please compute this
 hw.acpi.battery.time: remaining time in minutes
 and make it available at any time, and at any state of the machine.
 There is a good use for this data.