io_att Kernel Service

AIX Version 4.3 Kernel and Subsystems Technical Reference, Volume 1

Selects, allocates, and maps a region in the current address space for I/O access.

#include <sys/types.h>
#include <sys/errno.h>
#include <sys/vmuser.h>
#include <sys/adspace.h>

caddr_t io_att (iohandle, offset)
vmhandle_t iohandle;
caddr_t offset;

iohandle	Specifies a handle for the I/O object to be mapped in the current address space.
offset	Specifies the address offset in both the I/O space and the virtual memory region to be mapped.

Attention: The io_att service will crash the kernel if there are no more free regions.

The io_att kernel service performs these four tasks:

Selects an unallocated virtual memory region.
Allocates it.
Maps the I/O address space specified by the iohandle parameter with the access permission specified in the handle.
Constructs the address specified by the offset parameter in the current address space.

The io_att kernel service assumes an address space model of fixed-size I/O objects and virtual memory address space regions.

The io_att kernel service can be called from either the process or interrupt environment.

The io_att kernel service returns an address for the offset in the virtual memory address space.

The io_att kernel service is part of Base Operating System (BOS) Runtime.

The io_det kernel service.

Memory Kernel Services and Understanding Virtual Memory Manager Interfaces in AIX Kernel Extensions and Device Support Programming Concepts.