entread Ethernet Device Handler Entry Point

Purpose

Note: This function is supported in AIX® 5.1 and earlier only.

Provides the means of receiving data from the Ethernet device handler.

Syntax

#include <sys/device.h>
#include <sys/uio.h>

int entread (devno, uiop, chan, ext) dev_t devno; struct uio * uiop; int chan, ext;

Parameters

Item	Description
devno	Specifies major and minor device numbers.
uiop	Points to a uio structure. This structure is defined in the /usr/include/sys/uio.h file.
chan	Specifies the channel number assigned by the entmpx routine.
ext	Can specify the address of the entread parameter block. If the ext parameter is null, then no parameter block is specified.

Description

Note: The entread entry point should only be called by user-mode callers.

The entread entry point provides the means of receiving data from the Ethernet device handler. When a user-mode caller issues a read, readx, readv, or readvx subroutine, the kernel calls the entread entry point.

When the entread entry point is called, the file system fills in the uio structure fields with the appropriate values. In addition, the device handler copies the data into the buffer specified by the caller.

For the entread entry point, the ext parameter may point to the read_extension structure. This structure is defined in the /usr/include/sys/comio.h file and contains the following field:

Field	Description
`status`	Contains one of the following status codes: CIO_OK CIO_BUF_OVRFLW CIO_NOT_STARTED

The entread entry point functions with an Ethernet High-Performance LAN adapter that has been correctly configured for use on a qualified network. Consult the adapter specifications for more information on configuring the network adapter and network qualifications.

Execution Environment

An entread entry point can be called from the process environment only.

Return Values

In general, communication device handlers use the common return codes defined for an entry point. However, device handlers for specific communication devices may return device-specific codes. The common return codes for the entread entry point are the following:

Return Code	Description
EACCES	Indicates permission was denied because the device was already open. Diagnostic mode open request denied.
EFAULT	Indicates a specified address is not valid.
EINTR	Indicates an interrupted system call.
EIO	Indicates an I/O error.
EMSGSIZE	Indicates the data returned was too large for the buffer.
EBUSY	Indicates the maximum number of opens was exceeded.
ENODEV	Indicates the specified device does not exist.
ENOCONNECT	Indicates no connection was established.
ENXIO	Indicates an attempt to use an unconfigured device.