Advogato: How Linux Suspend and Resume Works in the ACPI Age

“Back in the APM days, everything was easy. You called an ioctl
on /dev/apm, and the kernel made a BIOS call. After that, it was
all up to the hardware. Sure, it never really worked properly, and
it was basically impossible to debug what the hardware actually
did. And then ACPI came along, and nothing worked at all. Several
years later, we’re almost back to where we were with APM. But
what’s actually happening when you hit that sleep key?

“Without the ability to suspend and resume, laptop users are
doomed to spend several hours of their lives waiting for machines
to boot and shutdown…”

Complete
Story