PSD_PORT_IO

PSD_PORT_IO keywords

Optional, Default, Can't Block

Description
Perform local port I/O.

Some platforms have some non MP specific system ports localized on a per-processor basis. If a local I/O operation may block before completion, I/O can be routed to a specific CPU for processing. This should be done, because an operation which started on one processor is not guaranteed to complete on that processor if execution is blocked. This function gets invoked as the result of a device driver calling DevHelp_Port_IO.

Mode
Called in Kernel, and Interrupt Mode.

Entry
Pointer to a PORT_IO structure.

Exit

NO_ERROR

if the I/O was successful.
-1
if the I/O wasn't successful.
Structures

typedef struct port_io_s{
   ulong_t port;   (Input)
   ulong_t data;   (Input/Output)
   ulong_t flags;  (Input)
} PORT_IO;

port

indicates which port to read to, or write from.
data
contains the data read from a read request, or the data to write if a write request. If the request uses less the 4 bytes the least significant portion of the data variable is used.
flags
indicate what operation to perform.

IO_READ_BYTE

Read a byte from the port
IO_READ_WORD
Read a word from the port
IO_READ_DWORD
Read a dword from the port
IO_WRITE_BYTE
Write a byte to the port
IO_WRITE_WORD
Write a word to the port
IO_WRITE_DWORD
Write a dword to the port
Notes
If the I/O performed is to a non-local port, the I/O should be handled as a regular I/O request.

If device drivers or applications access the local ports directly, instead of using the documented interfaces problems may occur.

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