fd(4/sparc64): replace disksort() with bufqs

[David Gwynne]

this is a port of the same change to the isa/fd.c code to the sparc64
driver. it effectively replaces disksort with nscan.

tests? ok?

Index: fd.c
===================================================================
RCS file: /cvs/src/sys/arch/sparc64/dev/fd.c,v
retrieving revision 1.40
diff -u -p -r1.40 fd.c
--- fd.c        20 Oct 2013 10:11:17 -0000      1.40
+++ fd.c        31 Oct 2013 03:34:14 -0000
@@ -267,7 +267,8 @@ struct fd_softc {
 
        TAILQ_ENTRY(fd_softc) sc_drivechain;
        int sc_ops;             /* I/O ops since last switch */
-       struct buf sc_q;        /* pending I/O requests */
+       struct bufq sc_bufq;    /* pending I/O requests */
+       struct buf *sc_bp;      /* current I/O */
 };
 
 /* floppy driver configuration */
@@ -669,6 +670,7 @@ fdattach(parent, self, aux)
         */
        fd->sc_dk.dk_flags = DKF_NOLABELREAD;
        fd->sc_dk.dk_name = fd->sc_dv.dv_xname;
+       bufq_init(&fd->sc_bufq, BUFQ_DEFAULT);
        disk_attach(&fd->sc_dv, &fd->sc_dk);
 }
 
@@ -752,11 +754,13 @@ fdstrategy(bp)
                    fd->sc_blkno, bp->b_cylinder);
 #endif
 
+       /* Queue transfer */
+       bufq_queue(&fd->sc_bufq, bp);
+
        /* Queue transfer on drive, activate drive and controller if idle. */
        s = splbio();
-       disksort(&fd->sc_q, bp);
        timeout_del(&fd->sc_motoroff_to);               /* a good idea */
-       if (!fd->sc_q.b_active)
+       if (fd->sc_bp == NULL)
                fdstart(fd);
 #ifdef DIAGNOSTIC
        else {
@@ -787,7 +791,7 @@ fdstart(fd)
        int active = !TAILQ_EMPTY(&fdc->sc_drives);
 
        /* Link into controller queue. */
-       fd->sc_q.b_active = 1;
+       fd->sc_bp = bufq_dequeue(&fd->sc_bufq);
        TAILQ_INSERT_TAIL(&fdc->sc_drives, fd, sc_drivechain);
 
        /* If controller not already active, start it. */
@@ -802,6 +806,9 @@ fdfinish(fd, bp)
 {
        struct fdc_softc *fdc = (void *)fd->sc_dv.dv_parent;
 
+       fd->sc_skip = 0;
+       fd->sc_bp = bufq_dequeue(&fd->sc_bufq);
+
        /*
         * Move this drive to the end of the queue to give others a `fair'
         * chance.  We only force a switch if N operations are completed while
@@ -811,15 +818,11 @@ fdfinish(fd, bp)
        if (TAILQ_NEXT(fd, sc_drivechain) != NULL && ++fd->sc_ops >= 8) {
                fd->sc_ops = 0;
                TAILQ_REMOVE(&fdc->sc_drives, fd, sc_drivechain);
-               if (bp->b_actf) {
+               if (fd->sc_bp != NULL)
                        TAILQ_INSERT_TAIL(&fdc->sc_drives, fd, sc_drivechain);
-               } else
-                       fd->sc_q.b_active = 0;
        }
-       bp->b_resid = fd->sc_bcount;
-       fd->sc_skip = 0;
-       fd->sc_q.b_actf = bp->b_actf;
 
+       bp->b_resid = fd->sc_bcount;
        biodone(bp);
        /* turn off motor 5s from now */
        timeout_add_sec(&fd->sc_motoroff_to, 5);
@@ -1140,7 +1143,7 @@ fdctimeout(arg)
                goto out;
        }
 
-       if (fd->sc_q.b_actf)
+       if (fd->sc_bp != NULL)
                fdc->sc_state++;
        else
                fdc->sc_state = DEVIDLE;
@@ -1317,11 +1320,10 @@ loop:
        }
 
        /* Is there a transfer to this drive?  If not, deactivate drive. */
-       bp = fd->sc_q.b_actf;
+       bp = fd->sc_bp;
        if (bp == NULL) {
                fd->sc_ops = 0;
                TAILQ_REMOVE(&fdc->sc_drives, fd, sc_drivechain);
-               fd->sc_q.b_active = 0;
                goto loop;
        }
 
@@ -1736,7 +1738,7 @@ fdcretry(fdc)
        int error = EIO;
 
        fd = TAILQ_FIRST(&fdc->sc_drives);
-       bp = fd->sc_q.b_actf;
+       bp = fd->sc_bp;
 
        fdc->sc_overruns = 0;
        if (fd->sc_opts & FDOPT_NORETRY)