ENXIOing non-present battery

[Dan Lukes]

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.

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.

Just my $0.02

Dan