rdsopen.c

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/* rdsopen.c - rdsopen */

#include <xinu.h>

/*------------------------------------------------------------------------
 * rdsopen  -  Open a remote disk device and specify an ID to use
 *------------------------------------------------------------------------
 */

devcall rdsopen (
     struct dentry  *devptr,    /* Entry in device switch table */
     char   *diskid,        /* Disk ID to use       */
     char   *mode           /* Unused for a remote disk */
    )
{
    struct  rdscblk *rdptr;     /* Ptr to control block entry   */
    struct  rd_msg_oreq msg;    /* Message to be sent       */
    struct  rd_msg_ores resp;   /* Buffer to hold response  */
    int32   retval;         /* Return value from rdscomm    */
    int32   len;            /* Counts chars in diskid   */
    char    *idto;          /* Ptr to ID string copy    */
    char    *idfrom;        /* Pointer into ID string   */

    rdptr = &rdstab[devptr->dvminor];

    /* Reject if device is already open */

    if (rdptr->rd_state != RD_FREE) {
        return SYSERR;
    }
    rdptr->rd_state = RD_PEND;

    /* Copy disk ID into free table slot */

    idto = rdptr->rd_id;
    idfrom = diskid;
    len = 0;
    while ( (*idto++ = *idfrom++) != NULLCH) {
        len++;
        if (len >= RD_IDLEN) {  /* ID string is too long */
            return SYSERR;
        }
    }

    /* Verify that name is non-null */

    if (len == 0) {
        return SYSERR;
    }

    /* Hand-craft an open request message to be sent to the server */

    msg.rd_type = htons(RD_MSG_OREQ);/* Request an open     */
    msg.rd_status = htons(0);
    msg.rd_seq = 0;         /* Rdscomm fills in an entry    */
    idto = msg.rd_id;
    memset(idto, NULLCH, RD_IDLEN);/* initialize ID to zero bytes   */

    idfrom = diskid;
    while ( (*idto++ = *idfrom++) != NULLCH ) { /* Copy ID to req.  */
        ;
    }

    /* Send message and receive response */

    retval = rdscomm((struct rd_msg_hdr *)&msg,
                    sizeof(struct rd_msg_oreq),
             (struct rd_msg_hdr *)&resp,
                    sizeof(struct rd_msg_ores),
                rdptr );

    /* Check response */

    if (retval == SYSERR) {
        rdptr->rd_state = RD_FREE;
        return SYSERR;
    } else if (retval == TIMEOUT) {
        kprintf("Timeout during remote file open\n\r");
        rdptr->rd_state = RD_FREE;
        return SYSERR;
    } else if (ntohs(resp.rd_status) != 0) {
        rdptr->rd_state = RD_FREE;
        return SYSERR;
    }

    /* Change state of device to indicate currently open */

    rdptr->rd_state = RD_OPEN;

    /* Return device descriptor */

    return devptr->dvnum;
}