msgqueue.c

Go to the documentation of this file.

/*
 *  linux/drivers/acorn/scsi/msgqueue.c
 *
 *  Copyright (C) 1997-1998 Russell King
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 *  message queue handling
 */
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/stddef.h>
#include <linux/init.h>

#include "msgqueue.h"

/*
 * Function: struct msgqueue_entry *mqe_alloc(MsgQueue_t *msgq)
 * Purpose : Allocate a message queue entry
 * Params  : msgq - message queue to claim entry for
 * Returns : message queue entry or NULL.
 */
static struct msgqueue_entry *mqe_alloc(MsgQueue_t *msgq)
{
    struct msgqueue_entry *mq;

    if ((mq = msgq->free) != NULL)
        msgq->free = mq->next;

    return mq;
}

/*
 * Function: void mqe_free(MsgQueue_t *msgq, struct msgqueue_entry *mq)
 * Purpose : free a message queue entry
 * Params  : msgq - message queue to free entry from
 *       mq   - message queue entry to free
 */
static void mqe_free(MsgQueue_t *msgq, struct msgqueue_entry *mq)
{
    if (mq) {
        mq->next = msgq->free;
        msgq->free = mq;
    }
}

/*
 * Function: void msgqueue_initialise(MsgQueue_t *msgq)
 * Purpose : initialise a message queue
 * Params  : msgq - queue to initialise
 */
void msgqueue_initialise(MsgQueue_t *msgq)
{
    int i;

    msgq->qe = NULL;
    msgq->free = &msgq->entries[0];

    for (i = 0; i < NR_MESSAGES; i++)
        msgq->entries[i].next = &msgq->entries[i + 1];

    msgq->entries[NR_MESSAGES - 1].next = NULL;
}


/*
 * Function: void msgqueue_free(MsgQueue_t *msgq)
 * Purpose : free a queue
 * Params  : msgq - queue to free
 */
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
 */
int msgqueue_msglength(MsgQueue_t *msgq)
{
    struct msgqueue_entry *mq = msgq->qe;
    int length = 0;

    for (mq = msgq->qe; mq; mq = mq->next)
        length += mq->msg.length;

    return length;
}

/*
 * Function: struct message *msgqueue_getmsg(MsgQueue_t *msgq, int msgno)
 * Purpose : return a message
 * Params  : msgq   - queue to obtain message from
 *     : msgno  - message number
 * Returns : pointer to message string, or NULL
 */
struct message *msgqueue_getmsg(MsgQueue_t *msgq, int msgno)
{
    struct msgqueue_entry *mq;

    for (mq = msgq->qe; mq && msgno; mq = mq->next, msgno--);

    return mq ? &mq->msg : NULL;
}

/*
 * 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
 */
int msgqueue_addmsg(MsgQueue_t *msgq, int length, ...)
{
    struct msgqueue_entry *mq = mqe_alloc(msgq);
    va_list ap;

    if (mq) {
        struct msgqueue_entry **mqp;
        int i;

        va_start(ap, length);
        for (i = 0; i < length; i++)
            mq->msg.msg[i] = va_arg(ap, unsigned int);
        va_end(ap);

        mq->msg.length = length;
        mq->msg.fifo = 0;
        mq->next = NULL;

        mqp = &msgq->qe;
        while (*mqp)
            mqp = &(*mqp)->next;

        *mqp = mq;
    }

    return mq != NULL;
}

/*
 * Function: void msgqueue_flush(MsgQueue_t *msgq)
 * Purpose : flush all messages from message queue
 * Params  : msgq - queue to flush
 */
void msgqueue_flush(MsgQueue_t *msgq)
{
    struct msgqueue_entry *mq, *mqnext;

    for (mq = msgq->qe; mq; mq = mqnext) {
        mqnext = mq->next;
        mqe_free(msgq, mq);
    }
    msgq->qe = NULL;
}

EXPORT_SYMBOL(msgqueue_initialise);
EXPORT_SYMBOL(msgqueue_free);
EXPORT_SYMBOL(msgqueue_msglength);
EXPORT_SYMBOL(msgqueue_getmsg);
EXPORT_SYMBOL(msgqueue_addmsg);
EXPORT_SYMBOL(msgqueue_flush);

MODULE_AUTHOR("Russell King");
MODULE_DESCRIPTION("SCSI message queue handling");
MODULE_LICENSE("GPL");