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ld.c revision 1.103
      1 /*	$NetBSD: ld.c,v 1.103 2017/08/20 15:58:43 mlelstv Exp $	*/
      2 
      3 /*-
      4  * Copyright (c) 1998, 2000 The NetBSD Foundation, Inc.
      5  * All rights reserved.
      6  *
      7  * This code is derived from software contributed to The NetBSD Foundation
      8  * by Andrew Doran and Charles M. Hannum.
      9  *
     10  * Redistribution and use in source and binary forms, with or without
     11  * modification, are permitted provided that the following conditions
     12  * are met:
     13  * 1. Redistributions of source code must retain the above copyright
     14  *    notice, this list of conditions and the following disclaimer.
     15  * 2. Redistributions in binary form must reproduce the above copyright
     16  *    notice, this list of conditions and the following disclaimer in the
     17  *    documentation and/or other materials provided with the distribution.
     18  *
     19  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
     20  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
     21  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     22  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
     23  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
     24  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
     25  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
     26  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
     27  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
     28  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
     29  * POSSIBILITY OF SUCH DAMAGE.
     30  */
     31 
     32 /*
     33  * Disk driver for use by RAID controllers.
     34  */
     35 
     36 #include <sys/cdefs.h>
     37 __KERNEL_RCSID(0, "$NetBSD: ld.c,v 1.103 2017/08/20 15:58:43 mlelstv Exp $");
     38 
     39 #include <sys/param.h>
     40 #include <sys/systm.h>
     41 #include <sys/kernel.h>
     42 #include <sys/device.h>
     43 #include <sys/queue.h>
     44 #include <sys/proc.h>
     45 #include <sys/buf.h>
     46 #include <sys/bufq.h>
     47 #include <sys/endian.h>
     48 #include <sys/disklabel.h>
     49 #include <sys/disk.h>
     50 #include <sys/dkio.h>
     51 #include <sys/stat.h>
     52 #include <sys/conf.h>
     53 #include <sys/fcntl.h>
     54 #include <sys/vnode.h>
     55 #include <sys/syslog.h>
     56 #include <sys/mutex.h>
     57 #include <sys/module.h>
     58 #include <sys/reboot.h>
     59 
     60 #include <dev/ldvar.h>
     61 
     62 static void	ldminphys(struct buf *bp);
     63 static bool	ld_suspend(device_t, const pmf_qual_t *);
     64 static bool	ld_shutdown(device_t, int);
     65 static int	ld_diskstart(device_t, struct buf *bp);
     66 static void	ld_iosize(device_t, int *);
     67 static int	ld_dumpblocks(device_t, void *, daddr_t, int);
     68 static void	ld_fake_geometry(struct ld_softc *);
     69 static void	ld_set_geometry(struct ld_softc *);
     70 static void	ld_config_interrupts (device_t);
     71 static int	ld_lastclose(device_t);
     72 static int	ld_discard(device_t, off_t, off_t);
     73 static int	ld_flush(device_t, bool);
     74 
     75 extern struct	cfdriver ld_cd;
     76 
     77 static dev_type_open(ldopen);
     78 static dev_type_close(ldclose);
     79 static dev_type_read(ldread);
     80 static dev_type_write(ldwrite);
     81 static dev_type_ioctl(ldioctl);
     82 static dev_type_strategy(ldstrategy);
     83 static dev_type_dump(lddump);
     84 static dev_type_size(ldsize);
     85 static dev_type_discard(lddiscard);
     86 
     87 const struct bdevsw ld_bdevsw = {
     88 	.d_open = ldopen,
     89 	.d_close = ldclose,
     90 	.d_strategy = ldstrategy,
     91 	.d_ioctl = ldioctl,
     92 	.d_dump = lddump,
     93 	.d_psize = ldsize,
     94 	.d_discard = lddiscard,
     95 	.d_flag = D_DISK | D_MPSAFE
     96 };
     97 
     98 const struct cdevsw ld_cdevsw = {
     99 	.d_open = ldopen,
    100 	.d_close = ldclose,
    101 	.d_read = ldread,
    102 	.d_write = ldwrite,
    103 	.d_ioctl = ldioctl,
    104 	.d_stop = nostop,
    105 	.d_tty = notty,
    106 	.d_poll = nopoll,
    107 	.d_mmap = nommap,
    108 	.d_kqfilter = nokqfilter,
    109 	.d_discard = lddiscard,
    110 	.d_flag = D_DISK | D_MPSAFE
    111 };
    112 
    113 static struct	dkdriver lddkdriver = {
    114 	.d_open = ldopen,
    115 	.d_close = ldclose,
    116 	.d_strategy = ldstrategy,
    117 	.d_iosize = ld_iosize,
    118 	.d_minphys  = ldminphys,
    119 	.d_diskstart = ld_diskstart,
    120 	.d_dumpblocks = ld_dumpblocks,
    121 	.d_lastclose = ld_lastclose,
    122 	.d_discard = ld_discard
    123 };
    124 
    125 void
    126 ldattach(struct ld_softc *sc, const char *default_strategy)
    127 {
    128 	device_t self = sc->sc_dv;
    129 	struct dk_softc *dksc = &sc->sc_dksc;
    130 
    131 	mutex_init(&sc->sc_mutex, MUTEX_DEFAULT, IPL_VM);
    132 	cv_init(&sc->sc_drain, "lddrain");
    133 
    134 	if ((sc->sc_flags & LDF_ENABLED) == 0) {
    135 		return;
    136 	}
    137 
    138 	/* Initialise dk and disk structure. */
    139 	dk_init(dksc, self, DKTYPE_LD);
    140 	disk_init(&dksc->sc_dkdev, dksc->sc_xname, &lddkdriver);
    141 
    142 	if (sc->sc_maxxfer > MAXPHYS)
    143 		sc->sc_maxxfer = MAXPHYS;
    144 
    145 	/* Build synthetic geometry if necessary. */
    146 	if (sc->sc_nheads == 0 || sc->sc_nsectors == 0 ||
    147 	    sc->sc_ncylinders == 0)
    148 	    ld_fake_geometry(sc);
    149 
    150 	sc->sc_disksize512 = sc->sc_secperunit * sc->sc_secsize / DEV_BSIZE;
    151 
    152 	if (sc->sc_flags & LDF_NO_RND)
    153 		dksc->sc_flags |= DKF_NO_RND;
    154 
    155 	/* Attach dk and disk subsystems */
    156 	dk_attach(dksc);
    157 	disk_attach(&dksc->sc_dkdev);
    158 	ld_set_geometry(sc);
    159 
    160 	bufq_alloc(&dksc->sc_bufq, default_strategy, BUFQ_SORT_RAWBLOCK);
    161 
    162 	/* Register with PMF */
    163 	if (!pmf_device_register1(dksc->sc_dev, ld_suspend, NULL, ld_shutdown))
    164 		aprint_error_dev(dksc->sc_dev,
    165 		    "couldn't establish power handler\n");
    166 
    167 	/* Discover wedges on this disk. */
    168 	config_interrupts(sc->sc_dv, ld_config_interrupts);
    169 }
    170 
    171 int
    172 ldadjqparam(struct ld_softc *sc, int xmax)
    173 {
    174 
    175 	mutex_enter(&sc->sc_mutex);
    176 	sc->sc_maxqueuecnt = xmax;
    177 	mutex_exit(&sc->sc_mutex);
    178 
    179 	return (0);
    180 }
    181 
    182 int
    183 ldbegindetach(struct ld_softc *sc, int flags)
    184 {
    185 	struct dk_softc *dksc = &sc->sc_dksc;
    186 	int rv = 0;
    187 
    188 	if ((sc->sc_flags & LDF_ENABLED) == 0)
    189 		return (0);
    190 
    191 	rv = disk_begindetach(&dksc->sc_dkdev, ld_lastclose, dksc->sc_dev, flags);
    192 
    193 	if (rv != 0)
    194 		return rv;
    195 
    196 	mutex_enter(&sc->sc_mutex);
    197 	sc->sc_maxqueuecnt = 0;
    198 
    199 	while (sc->sc_queuecnt > 0) {
    200 		sc->sc_flags |= LDF_DRAIN;
    201 		cv_wait(&sc->sc_drain, &sc->sc_mutex);
    202 	}
    203 	mutex_exit(&sc->sc_mutex);
    204 
    205 	return (rv);
    206 }
    207 
    208 void
    209 ldenddetach(struct ld_softc *sc)
    210 {
    211 	struct dk_softc *dksc = &sc->sc_dksc;
    212 	int bmaj, cmaj, i, mn;
    213 
    214 	if ((sc->sc_flags & LDF_ENABLED) == 0)
    215 		return;
    216 
    217 	mutex_enter(&sc->sc_mutex);
    218 
    219 	/* Wait for commands queued with the hardware to complete. */
    220 	if (sc->sc_queuecnt != 0) {
    221 		if (cv_timedwait(&sc->sc_drain, &sc->sc_mutex, 30 * hz))
    222 			printf("%s: not drained\n", dksc->sc_xname);
    223 	}
    224 	mutex_exit(&sc->sc_mutex);
    225 
    226 	/* Kill off any queued buffers. */
    227 	dk_drain(dksc);
    228 	bufq_free(dksc->sc_bufq);
    229 
    230 	/* Locate the major numbers. */
    231 	bmaj = bdevsw_lookup_major(&ld_bdevsw);
    232 	cmaj = cdevsw_lookup_major(&ld_cdevsw);
    233 
    234 	/* Nuke the vnodes for any open instances. */
    235 	for (i = 0; i < MAXPARTITIONS; i++) {
    236 		mn = DISKMINOR(device_unit(dksc->sc_dev), i);
    237 		vdevgone(bmaj, mn, mn, VBLK);
    238 		vdevgone(cmaj, mn, mn, VCHR);
    239 	}
    240 
    241 	/* Delete all of our wedges. */
    242 	dkwedge_delall(&dksc->sc_dkdev);
    243 
    244 	/* Detach from the disk list. */
    245 	disk_detach(&dksc->sc_dkdev);
    246 	disk_destroy(&dksc->sc_dkdev);
    247 
    248 	dk_detach(dksc);
    249 
    250 	/* Deregister with PMF */
    251 	pmf_device_deregister(dksc->sc_dev);
    252 
    253 	/*
    254 	 * XXX We can't really flush the cache here, because the
    255 	 * XXX device may already be non-existent from the controller's
    256 	 * XXX perspective.
    257 	 */
    258 #if 0
    259 	ld_flush(dksc->sc_dev, false);
    260 #endif
    261 	cv_destroy(&sc->sc_drain);
    262 	mutex_destroy(&sc->sc_mutex);
    263 }
    264 
    265 /* ARGSUSED */
    266 static bool
    267 ld_suspend(device_t dev, const pmf_qual_t *qual)
    268 {
    269 	return ld_shutdown(dev, 0);
    270 }
    271 
    272 /* ARGSUSED */
    273 static bool
    274 ld_shutdown(device_t dev, int flags)
    275 {
    276 	if ((flags & RB_NOSYNC) == 0 && ld_flush(dev, true) != 0)
    277 		return false;
    278 
    279 	return true;
    280 }
    281 
    282 /* ARGSUSED */
    283 static int
    284 ldopen(dev_t dev, int flags, int fmt, struct lwp *l)
    285 {
    286 	struct ld_softc *sc;
    287 	struct dk_softc *dksc;
    288 	int unit;
    289 
    290 	unit = DISKUNIT(dev);
    291 	if ((sc = device_lookup_private(&ld_cd, unit)) == NULL)
    292 		return (ENXIO);
    293 	dksc = &sc->sc_dksc;
    294 
    295 	return dk_open(dksc, dev, flags, fmt, l);
    296 }
    297 
    298 static int
    299 ld_lastclose(device_t self)
    300 {
    301 	ld_flush(self, false);
    302 
    303 	return 0;
    304 }
    305 
    306 /* ARGSUSED */
    307 static int
    308 ldclose(dev_t dev, int flags, int fmt, struct lwp *l)
    309 {
    310 	struct ld_softc *sc;
    311 	struct dk_softc *dksc;
    312 	int unit;
    313 
    314 	unit = DISKUNIT(dev);
    315 	sc = device_lookup_private(&ld_cd, unit);
    316 	dksc = &sc->sc_dksc;
    317 
    318 	return dk_close(dksc, dev, flags, fmt, l);
    319 }
    320 
    321 /* ARGSUSED */
    322 static int
    323 ldread(dev_t dev, struct uio *uio, int ioflag)
    324 {
    325 
    326 	return (physio(ldstrategy, NULL, dev, B_READ, ldminphys, uio));
    327 }
    328 
    329 /* ARGSUSED */
    330 static int
    331 ldwrite(dev_t dev, struct uio *uio, int ioflag)
    332 {
    333 
    334 	return (physio(ldstrategy, NULL, dev, B_WRITE, ldminphys, uio));
    335 }
    336 
    337 /* ARGSUSED */
    338 static int
    339 ldioctl(dev_t dev, u_long cmd, void *addr, int32_t flag, struct lwp *l)
    340 {
    341 	struct ld_softc *sc;
    342 	struct dk_softc *dksc;
    343 	int unit, error;
    344 
    345 	unit = DISKUNIT(dev);
    346 	sc = device_lookup_private(&ld_cd, unit);
    347 	dksc = &sc->sc_dksc;
    348 
    349 	error = 0;
    350 
    351 	/*
    352 	 * Some common checks so that individual attachments wouldn't need
    353 	 * to duplicate them.
    354 	 */
    355 	switch (cmd) {
    356 	case DIOCCACHESYNC:
    357 		/*
    358 		 * XXX Do we really need to care about having a writable
    359 		 * file descriptor here?
    360 		 */
    361 		if ((flag & FWRITE) == 0)
    362 			error = EBADF;
    363 		else
    364 			error = 0;
    365 		break;
    366 	}
    367 
    368 	if (error != 0)
    369 		return (error);
    370 
    371 	if (sc->sc_ioctl) {
    372 		error = (*sc->sc_ioctl)(sc, cmd, addr, flag, 0);
    373 		if (error != EPASSTHROUGH)
    374 			return (error);
    375 	}
    376 
    377 	/* something not handled by the attachment */
    378 	return dk_ioctl(dksc, dev, cmd, addr, flag, l);
    379 }
    380 
    381 /*
    382  * Flush the device's cache.
    383  */
    384 static int
    385 ld_flush(device_t self, bool poll)
    386 {
    387 	int error = 0;
    388 	struct ld_softc *sc = device_private(self);
    389 
    390 	if (sc->sc_ioctl) {
    391 		error = (*sc->sc_ioctl)(sc, DIOCCACHESYNC, NULL, 0, poll);
    392 		if (error != 0)
    393 			device_printf(self, "unable to flush cache\n");
    394 	}
    395 
    396 	return error;
    397 }
    398 
    399 static void
    400 ldstrategy(struct buf *bp)
    401 {
    402 	struct ld_softc *sc;
    403 	struct dk_softc *dksc;
    404 	int unit;
    405 
    406 	unit = DISKUNIT(bp->b_dev);
    407 	sc = device_lookup_private(&ld_cd, unit);
    408 	dksc = &sc->sc_dksc;
    409 
    410 	dk_strategy(dksc, bp);
    411 }
    412 
    413 static int
    414 ld_diskstart(device_t dev, struct buf *bp)
    415 {
    416 	struct ld_softc *sc = device_private(dev);
    417 	int error;
    418 
    419 	if (sc->sc_queuecnt >= sc->sc_maxqueuecnt)
    420 		return EAGAIN;
    421 
    422 	if ((sc->sc_flags & LDF_MPSAFE) == 0)
    423 		KERNEL_LOCK(1, curlwp);
    424 
    425 	mutex_enter(&sc->sc_mutex);
    426 
    427 	if (sc->sc_queuecnt >= sc->sc_maxqueuecnt)
    428 		error = EAGAIN;
    429 	else {
    430 		error = (*sc->sc_start)(sc, bp);
    431 		if (error == 0)
    432 			sc->sc_queuecnt++;
    433 	}
    434 
    435 	mutex_exit(&sc->sc_mutex);
    436 
    437 	if ((sc->sc_flags & LDF_MPSAFE) == 0)
    438 		KERNEL_UNLOCK_ONE(curlwp);
    439 
    440 	return error;
    441 }
    442 
    443 void
    444 lddone(struct ld_softc *sc, struct buf *bp)
    445 {
    446 	struct dk_softc *dksc = &sc->sc_dksc;
    447 
    448 	dk_done(dksc, bp);
    449 
    450 	mutex_enter(&sc->sc_mutex);
    451 	if (--sc->sc_queuecnt <= sc->sc_maxqueuecnt) {
    452 		if ((sc->sc_flags & LDF_DRAIN) != 0) {
    453 			sc->sc_flags &= ~LDF_DRAIN;
    454 			cv_broadcast(&sc->sc_drain);
    455 		}
    456 		mutex_exit(&sc->sc_mutex);
    457 		dk_start(dksc, NULL);
    458 	} else
    459 		mutex_exit(&sc->sc_mutex);
    460 }
    461 
    462 static int
    463 ldsize(dev_t dev)
    464 {
    465 	struct ld_softc *sc;
    466 	struct dk_softc *dksc;
    467 	int unit;
    468 
    469 	unit = DISKUNIT(dev);
    470 	if ((sc = device_lookup_private(&ld_cd, unit)) == NULL)
    471 		return (-1);
    472 	dksc = &sc->sc_dksc;
    473 
    474 	if ((sc->sc_flags & LDF_ENABLED) == 0)
    475 		return (-1);
    476 
    477 	return dk_size(dksc, dev);
    478 }
    479 
    480 /*
    481  * Take a dump.
    482  */
    483 static int
    484 lddump(dev_t dev, daddr_t blkno, void *va, size_t size)
    485 {
    486 	struct ld_softc *sc;
    487 	struct dk_softc *dksc;
    488 	int unit;
    489 
    490 	unit = DISKUNIT(dev);
    491 	if ((sc = device_lookup_private(&ld_cd, unit)) == NULL)
    492 		return (ENXIO);
    493 	dksc = &sc->sc_dksc;
    494 
    495 	if ((sc->sc_flags & LDF_ENABLED) == 0)
    496 		return (ENODEV);
    497 
    498 	return dk_dump(dksc, dev, blkno, va, size);
    499 }
    500 
    501 static int
    502 ld_dumpblocks(device_t dev, void *va, daddr_t blkno, int nblk)
    503 {
    504 	struct ld_softc *sc = device_private(dev);
    505 
    506 	if (sc->sc_dump == NULL)
    507 		return (ENODEV);
    508 
    509 	return (*sc->sc_dump)(sc, va, blkno, nblk);
    510 }
    511 
    512 /*
    513  * Adjust the size of a transfer.
    514  */
    515 static void
    516 ldminphys(struct buf *bp)
    517 {
    518 	int unit;
    519 	struct ld_softc *sc;
    520 
    521 	unit = DISKUNIT(bp->b_dev);
    522 	sc = device_lookup_private(&ld_cd, unit);
    523 
    524 	ld_iosize(sc->sc_dv, &bp->b_bcount);
    525 	minphys(bp);
    526 }
    527 
    528 static void
    529 ld_iosize(device_t d, int *countp)
    530 {
    531 	struct ld_softc *sc = device_private(d);
    532 
    533 	if (*countp > sc->sc_maxxfer)
    534 		*countp = sc->sc_maxxfer;
    535 }
    536 
    537 static void
    538 ld_fake_geometry(struct ld_softc *sc)
    539 {
    540 	uint64_t ncyl;
    541 
    542 	if (sc->sc_secperunit <= 528 * 2048)		/* 528MB */
    543 		sc->sc_nheads = 16;
    544 	else if (sc->sc_secperunit <= 1024 * 2048)	/* 1GB */
    545 		sc->sc_nheads = 32;
    546 	else if (sc->sc_secperunit <= 21504 * 2048)	/* 21GB */
    547 		sc->sc_nheads = 64;
    548 	else if (sc->sc_secperunit <= 43008 * 2048)	/* 42GB */
    549 		sc->sc_nheads = 128;
    550 	else
    551 		sc->sc_nheads = 255;
    552 
    553 	sc->sc_nsectors = 63;
    554 	sc->sc_ncylinders = INT_MAX;
    555 	ncyl = sc->sc_secperunit /
    556 	    (sc->sc_nheads * sc->sc_nsectors);
    557 	if (ncyl < INT_MAX)
    558 		sc->sc_ncylinders = (int)ncyl;
    559 }
    560 
    561 static void
    562 ld_set_geometry(struct ld_softc *sc)
    563 {
    564 	struct dk_softc *dksc = &sc->sc_dksc;
    565 	struct disk_geom *dg = &dksc->sc_dkdev.dk_geom;
    566 	char tbuf[9];
    567 
    568 	format_bytes(tbuf, sizeof(tbuf), sc->sc_secperunit *
    569 	    sc->sc_secsize);
    570 	aprint_normal_dev(dksc->sc_dev, "%s, %d cyl, %d head, %d sec, "
    571 	    "%d bytes/sect x %"PRIu64" sectors\n",
    572 	    tbuf, sc->sc_ncylinders, sc->sc_nheads,
    573 	    sc->sc_nsectors, sc->sc_secsize, sc->sc_secperunit);
    574 
    575 	memset(dg, 0, sizeof(*dg));
    576 	dg->dg_secperunit = sc->sc_secperunit;
    577 	dg->dg_secsize = sc->sc_secsize;
    578 	dg->dg_nsectors = sc->sc_nsectors;
    579 	dg->dg_ntracks = sc->sc_nheads;
    580 	dg->dg_ncylinders = sc->sc_ncylinders;
    581 
    582 	disk_set_info(dksc->sc_dev, &dksc->sc_dkdev, NULL);
    583 }
    584 
    585 static void
    586 ld_config_interrupts(device_t d)
    587 {
    588 	struct ld_softc *sc = device_private(d);
    589 	struct dk_softc *dksc = &sc->sc_dksc;
    590 
    591 	dkwedge_discover(&dksc->sc_dkdev);
    592 }
    593 
    594 static int
    595 ld_discard(device_t dev, off_t pos, off_t len)
    596 {
    597 	struct ld_softc *sc = device_private(dev);
    598 	struct buf dbuf, *bp = &dbuf;
    599 	int error = 0;
    600 
    601 	KASSERT(len <= INT_MAX);
    602 
    603 	if (sc->sc_discard == NULL)
    604 		return (ENODEV);
    605 
    606 	if ((sc->sc_flags & LDF_MPSAFE) == 0)
    607 		KERNEL_LOCK(1, curlwp);
    608 
    609 	buf_init(bp);
    610 	bp->b_vp = NULL;
    611 	bp->b_data = NULL;
    612 	bp->b_bufsize = 0;
    613 	bp->b_rawblkno = pos / sc->sc_secsize;
    614 	bp->b_bcount = len;
    615 	bp->b_flags = B_WRITE;
    616 	bp->b_cflags = BC_BUSY;
    617 
    618 	error = (*sc->sc_discard)(sc, bp);
    619 	if (error == 0)
    620 		error = biowait(bp);
    621 
    622 	buf_destroy(bp);
    623 
    624 	if ((sc->sc_flags & LDF_MPSAFE) == 0)
    625 		KERNEL_UNLOCK_ONE(curlwp);
    626 
    627 	return error;
    628 }
    629 
    630 void
    631 lddiscardend(struct ld_softc *sc, struct buf *bp)
    632 {
    633 
    634 	if (bp->b_error)
    635 		bp->b_resid = bp->b_bcount;
    636 	biodone(bp);
    637 }
    638 
    639 static int
    640 lddiscard(dev_t dev, off_t pos, off_t len)
    641 {
    642 	struct ld_softc *sc;
    643 	struct dk_softc *dksc;
    644 	int unit;
    645 
    646 	unit = DISKUNIT(dev);
    647 	sc = device_lookup_private(&ld_cd, unit);
    648 	dksc = &sc->sc_dksc;
    649 
    650 	return dk_discard(dksc, dev, pos, len);
    651 }
    652 
    653 MODULE(MODULE_CLASS_DRIVER, ld, "dk_subr");
    654 
    655 #ifdef _MODULE
    656 CFDRIVER_DECL(ld, DV_DISK, NULL);
    657 #endif
    658 
    659 static int
    660 ld_modcmd(modcmd_t cmd, void *opaque)
    661 {
    662 #ifdef _MODULE
    663 	devmajor_t bmajor, cmajor;
    664 #endif
    665 	int error = 0;
    666 
    667 #ifdef _MODULE
    668 	switch (cmd) {
    669 	case MODULE_CMD_INIT:
    670 		bmajor = cmajor = -1;
    671 		error = devsw_attach(ld_cd.cd_name, &ld_bdevsw, &bmajor,
    672 		    &ld_cdevsw, &cmajor);
    673 		if (error)
    674 			break;
    675 		error = config_cfdriver_attach(&ld_cd);
    676 		break;
    677 	case MODULE_CMD_FINI:
    678 		error = config_cfdriver_detach(&ld_cd);
    679 		if (error)
    680 			break;
    681 		devsw_detach(&ld_bdevsw, &ld_cdevsw);
    682 		break;
    683 	default:
    684 		error = ENOTTY;
    685 		break;
    686 	}
    687 #endif
    688 
    689 	return error;
    690 }
    691