acpi_ibm(4): new radio kill switch (readonly) sysctl

[Sam Leffler]

Rong-en Fan wrote:
> As pointed out by Henrik Brix Andersen, I adds a sysctl entry
> that shows the status of radio kill switch found on some ThinkPad:
> 
> http://people.freebsd.org/~rafan/acpi_ibm_killswitch.diff
> 
> dev.acpi_ibm.0.killswitch = 0 means the switch is off. It seems that
> no acpi event will be generated when the value changes (actually,
> my x60 does not generate any events when I presses FN+something).
> Otherwise, we can hook it in devd.conf and remove wireless driver when
> kill switch is on...
> 
> Any comments?

If the radio is Atheros-based the kill switch likely generates a GPIO
interrupt that the ath driver can catch and use to turn the radio on/off.

	Sam