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The following mechanisms are OSPM specific:
1. Redirect output destination to console: no file redirection will be
   needed by an in-kernel debugger, there is even no file can be accessed
   when the debugger is running in the kernel mode.
2. Output command prompts: programs other than acpiexec can have different
   prompt characters and the prompt characters may be implemented as a
   special character sequence to form a char device IO protocol.
3. Command ready/complete handshake: OSPM debugger may wait more conditions
   to implement OSPM specific semantics (for example, FIFO full/empty
   conditions for O_NONBLOCK or IO open/close conditions).
Leaving such OSPM specific stuffs in the ACPICA debugger core blocks
Linux debugger IO driver implementation.

Several new OSL APIs are provided by this patch:
1. acpi_os_initialize_command_signals: initialize command handshake mechanism
   or any other OSPM specific stuffs.
2. acpi_os_terminate_command...