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Technical Reference: Kernel and Subsystems, Volume 2

tokfastwrt Token-Ring Device Handler Entry Point


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

Provides the means for kernel users to perform direct-access write operations.


#include <sys/device.h>
#include <sys/comio.h>
#include <sys/tokuser.h>
#include <sys/mbuf.h>

int tokfastwrt (devno, m)
dev_t devno;
struct mbuf *m;


devno Specifies major and minor device numbers.
m Pointer to an mbuf structure containing the data to transmit.


The tokfastwrt entry point is called from a kernel-mode process to pass a write packet to the token-ring device handler for subsequent transmission. The address of this entry point is provided to the kernel user by the CIO_GET_FASTWRT ioctl entry point.

The tokfastwrt entry point provides for only one data packet to be transmitted for a single tokfastwrt call. The tokfastwrt entry point assumes that the calling user is a valid kernel user and that the mbuf structure contains a valid data packet. The device handler frees the mbuf and does not acknowledge transmit completion.

The tokfastwrt entry point functions with a Token-Ring High-Performance Network Adapter that has been correctly configured for use on a qualified network. Consult adapter specifications for more information on configuring the adapter and network qualifications.

Execution Environment

The tokfastwrt entry point can be called from a kernel process or interrupt level. The operation level of the token-ring device handler is TOK_OPLEVEL. This label is defined in the /usr/include/sys/tokuser.h file. The tokfastwrt entry point treats this path as a trusted path and the device handler does not check the parameters.

Return Values

ENODEV Indicates the specified minor number is not valid.
EAGAIN Indicates the transmit queue is full.

Related Information

The tokmpx entry point, tokopen entry point.

The CIO_GET_FASTWRT tokioctl Token-Ring Device Handler Operation, CIO_START tokioctl Token-Ring Device Handler Operation.

The Memory Buffer (mbuf) Kernel Services in AIX 5L Version 5.2 Kernel Extensions and Device Support Programming Concepts.

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