[coreboot] what happened when power button is pressed and a machine begins to shutdown?

[Jiang Wang]

Hi

I am trying to understand how the power button pressing event triggers
the machine to shutdown. From the ACPI spec 4.7.2.2.1, it mentioned
that the power button can be implemented either as a fixed hardware or
a generic hardware programming method.  So, for ASUS M2V-MX SE, how
the power button is implemented?

I tested coreboot with Linux on M2V-MX SE. When the Linux stops at
login window, pressing the power button can lead the machine to
shutdown. So what are the concrete steps between the power button is
pressed to the Linux begins to shutdown? Is it a AML code get
executed? (but I read the M2V-MX SE dsdt source file, and didn't find
anything related to power button.) Will the event go to the BIOS
first? Then go to the OS? Or it is completely handled by OS?

The problem I try to solve is to find out whether BIOS can get the
button event before the OS and do something without OS.

Also, for the power button override event, it is completely handled by
hardware, right? Is it possible to trigger this event from the BIOS?

My questions may seem to be a little bit strange. Feel free to let me
know, If you still not clear about the questions. Thanks.

Regards,

Jiang