POWER(4) - Device Drivers Manual (hppa) #

POWER(4) - Device Drivers Manual (hppa)

NAME #

power - power button and power fail support

SYNOPSIS #

power0 at mainbus?

DESCRIPTION #

HP PA-RISC machines support power failure detection in different forms:

• “soft” power button
• power failure interrupt

The power driver tries its best to determine the power failure condition that is a result of a power button being depressed or a power supply system failure or a similar condition. Upon detection of any of the aforementioned conditions, it tries to gracefully (if possible) shutdown the system through a call to the boot(9) function.

On systems equipped with the lasi(4) bus adapter, we find a “soft” power button which upon depression gives us a signal in the “power register” and thus polling periodically we detect the event. Since that bit comes directly from the power button without any dampening, we perform a second long delay; thus quick transitions off and on will not result in a shutdown.

On modern systems, an interruption is signalled upon the power button depression and thus this avoids polling and does not require (as does being implemented in hardware) dampening.

SEE ALSO #

intro(4), lasi(4), pdc(4), boot(9)

HISTORY #

The power driver appeared in OpenBSD 3.4.

OpenBSD 7.5 - May 31, 2007