ACPI: question about functional but not present PnP serial device

ACPI: question about functional but not present PnP serial device

[Shan Wei]

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hi
 
  if the status of one serial device is not present
but functional, it's driver is not be loaded on boot,
and the device are not be startup , yes or no？

   and my question is when is the status of device 
not present but functional.

   After adding a serial device(e.g. ttyS0) on the 
/etc/inittab, when booting the kernel, is the status 
of the device not present but functional?