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Annotation of xinu/sys/LSI/dskenq.c, revision 1.1

1.1     ! root        1: /* dskenq.c - dskenq */
        !             2: 
        !             3: #include <conf.h>
        !             4: #include <kernel.h>
        !             5: #include <disk.h>
        !             6: 
        !             7: /*------------------------------------------------------------------------
        !             8:  *  dskenq  --  enqueue a disk request and start I/O if disk not busy
        !             9:  *------------------------------------------------------------------------
        !            10:  */
        !            11: dskenq(drptr, dsptr)
        !            12:        struct  dreq    *drptr;
        !            13:        struct  dsblk   *dsptr;
        !            14: {
        !            15:        struct  dreq    *p, *q;         /* q follows p through requests */
        !            16:        DBADDR  block;
        !            17:        int     st;
        !            18: 
        !            19:        if ( (q=dsptr->dreqlst) == DRNULL ) {
        !            20:                dsptr->dreqlst = drptr;
        !            21:                drptr->drnext = DRNULL;
        !            22:                dskstrt(dsptr);
        !            23:                return(DONQ);
        !            24:        }
        !            25:        block = drptr->drdba;
        !            26:        for (p = q->drnext ; p != DRNULL ; q=p,p=p->drnext) {
        !            27:                if (p->drdba==block && (st=dskqopt(p, q, drptr)!=SYSERR))
        !            28:                                return(st);
        !            29:                if ( (q->drdba <= block && block < p->drdba) ||
        !            30:                     (q->drdba >= block && block > p->drdba)   ) {
        !            31:                        drptr->drnext = p;
        !            32:                        q->drnext = drptr;
        !            33:                        return(DONQ);
        !            34:                }
        !            35:        }
        !            36:        drptr->drnext = DRNULL;
        !            37:        q->drnext = drptr;
        !            38:        return(DONQ);
        !            39: }

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