/* SPDX-License-Identifier: GPL-2.0-only *//* *  linux/drivers/acorn/scsi/msgqueue.h * *  Copyright (C) 1997 Russell King * *  message queue handling */#ifndef MSGQUEUE_H#define MSGQUEUE_H struct message {    char msg[8];    int length;    int fifo;}; struct msgqueue_entry {    struct message msg;    struct msgqueue_entry *next;}; #define NR_MESSAGES 4 typedef struct {    struct msgqueue_entry *qe;    struct msgqueue_entry *free;    struct msgqueue_entry entries[NR_MESSAGES];} MsgQueue_t; /* * Function: void msgqueue_initialise(MsgQueue_t *msgq) * Purpose : initialise a message queue * Params  : msgq - queue to initialise */extern void msgqueue_initialise(MsgQueue_t *msgq); /* * Function: void msgqueue_free(MsgQueue_t *msgq) * Purpose : free a queue * Params  : msgq - queue to free */extern void msgqueue_free(MsgQueue_t *msgq); /* * Function: int msgqueue_msglength(MsgQueue_t *msgq) * Purpose : calculate the total length of all messages on the message queue * Params  : msgq - queue to examine * Returns : number of bytes of messages in queue */extern int msgqueue_msglength(MsgQueue_t *msgq); /* * Function: struct message *msgqueue_getmsg(MsgQueue_t *msgq, int msgno) * Purpose : return a message & its length * Params  : msgq   - queue to obtain message from *         : msgno  - message number * Returns : pointer to message string, or NULL */extern struct message *msgqueue_getmsg(MsgQueue_t *msgq, int msgno); /* * Function: int msgqueue_addmsg(MsgQueue_t *msgq, int length, ...) * Purpose : add a message onto a message queue * Params  : msgq   - queue to add message on *	     length - length of message *	     ...    - message bytes * Returns : != 0 if successful */extern int msgqueue_addmsg(MsgQueue_t *msgq, int length, ...); /* * Function: void msgqueue_flush(MsgQueue_t *msgq) * Purpose : flush all messages from message queue * Params  : msgq - queue to flush */extern void msgqueue_flush(MsgQueue_t *msgq); #endif