DosPortAccess

This call requests or releases access to ports for I/O privilege.

DosPortAccess

(Reserved, TypeOfAccess, FirstPort, LastPort)

Reserved (USHORT) - input

Must be set to zero.
TypeOfAccess (USHORT) - input
A request for or release of access to a port.

Value

Definition
0
Request access
1
Release access.
FirstPort (USHORT) - input
Starting (low) number in a contiguous range or a single port.
LastPort (USHORT) - input
Ending (high) number in a contiguous range or a single port. If only one port is being used, FirstPort and LastPort should both be set to this port.
rc (USHORT) - return
Return code descriptions are:
• NO_ERROR 5
  ERROR_ACCESS_DENIED
  Remarks

  Note that CLI/STI privilege is also granted automatically. There is no need to make an additional call to DosCLIAccess.

  Applications that perform I/O to port(s) in IOPL segments must request port access from the operating system.

  An application with no IOPL segments that accesses a device through a device driver or by an interface package such as VIO, does not need to issue this call. The device driver or interface package is responsible for obtaining the necessary I/O access.

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