PSD_PORT_IO

PSD_PORT_IO keywords

Optional, Default, Can't Block

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.

Called in Kernel, and Interrupt Mode.

Pointer to a PORT_IO structure.

if the I/O was successful.

if the I/O wasn't successful.

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

indicates which port to read to, or write from.

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.

indicate what operation to perform.

Read a byte from the port

Read a word from the port

Read a dword from the port

Write a byte to the port

Write a word to the port

Write a dword to the port

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.