ioapic_read
apic_id = ioapic_read(apic, IOAPIC_ID) >> APIC_ID_SHIFT;
static u_int ioapic_read(volatile ioapic_t *apic, int reg);
low = ioapic_read(io->io_addr,
value = ioapic_read(apic, IOAPIC_VER);
io->io_hw_apic_id = ioapic_read(apic, IOAPIC_ID) >> APIC_ID_SHIFT;
value = ioapic_read(apic, IOAPIC_REDTBL_LO(i));
flags = ioapic_read(apic, IOAPIC_VER) & IOART_VER_VERSION;