ENXIOing non-present battery

[Colin Percival]

On 12/07/14 00:28, Dan Lukes wrote:
> Colin Percival wrote:
>> it seems like not attaching a non-present battery would be a good idea.  This shouldn't be the default behaviour, since
>> there are plenty of systems where a non-present battery might be inserted at
>> a later time; but I see nothing wrong with adding an option.
>>
>> The attached patch adds a acpi.cmbat.hide_not_present loader tunable which,
>> as the name suggests, hides non-present batteries; this is done in the probe
>> code by returning ENXIO
>>
>> Any objections to me committing this?
> 
> No, but it may be more useful to create more generalized interface.

I agree in theory, but do you have any idea how to do this?

> A remember broken ACPI with issues related to ghost floppy drive when no
> real floppy drive has been present.
> 
> Not only battery, but any device should be considered non-attachable
> upon administrator request.

In the case of my laptop, the only way I can see to distinguish between the
real battery and the "ghost" battery is that the latter returns zero from
acpi_BatteryIsPresent; and that won't work for non-battery devices.

There is, of course, the option of using debug.apci.disabled to disable
complete subsystems, but I only want to hide the ghost battery, not the
real one.

-- 
Colin Percival
Security Officer Emeritus, FreeBSD | The power to serve
Founder, Tarsnap | www.tarsnap.com | Online backups for the truly paranoid