uiomove Kernel Service

Purpose

Moves a block of data between kernel space and a space defined by a uio structure.

Syntax

#include <sys/types.h>
#include <sys/errno.h>
#include <sys/uio.h>

int uiomove ( cp, n, rw, uiop) caddr_t cp; int n; uio_rw rw; struct uio *uiop;

Parameters

Item	Description
cp	Specifies the address in kernel memory to or from which data is moved.
n	Specifies the number of bytes to move.
rw	Indicates the direction of the move: UIO_READ Copies data from kernel space to space described by the uio structure. UIO_WRITE Copies data from space described by the uio structure to kernel space.
uiop	Points to a uio structure describing the buffer used in the data transfer.

Description

The uiomove kernel service moves the specified number of bytes of data between kernel space and a space described by a uio structure. Device driver top halves, especially character device drivers, frequently use the uiomove service to transfer data into or out of a user area. The uio_resid and uio_iovcnt fields in the uio structure describing the data area must be greater than 0 or an error is returned.

The uiomove service moves the number of bytes of data specified by either the n or uio_resid parameter, whichever is less. If either the n or uio_resid parameter is 0, no data is moved. The uio_segflg field in the uio structure is used to indicate if the move is accessing a user- or kernel-data area, or if the caller requires cross-memory operations and has provided the required cross-memory descriptors. If a cross-memory operation is indicated, there must be a cross-memory descriptor in the uio_xmem array for each iovec element.

If the move is successful, the following fields in the uio structure are updated:

Field	Description
`uio_iov`	Specifies the address of current `iovec` element to use.
`uio_xmem`	Specifies the address of the current `xmem` element to use.
`uio_iovcnt`	Specifies the number of remaining `iovec` elements.
`uio_iovdcnt`	Specifies the number of already processed `iovec` elements.
`uio_offset`	Specifies the character offset on the device performing the I/O.
`uio_resid`	Specifies the total number of characters remaining in the data area described by the uio structure.
`iov_base`	Specifies the address of the data area described by the current `iovec` element.
`iov_len`	Specifies the length of remaining data area in the buffer described by the current `iovec` element.

Execution Environment

The uiomove kernel service can be called from the process environment only.

Return Values

Item	Description
0	Indicates successful completion.
ENOMEM	Indicates that there was no room in the buffer.
EIO	Indicates a permanent I/O error file space.
ENOSPC	Indicates insufficient disk space.
EFAULT	Indicates a user location that is not valid.