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st_scsi.c revision 1.23.12.1
      1  1.23.12.1      tron /*	$NetBSD: st_scsi.c,v 1.23.12.1 2006/03/31 09:45:25 tron Exp $ */
      2        1.1    bouyer 
      3        1.1    bouyer /*-
      4       1.13   mycroft  * Copyright (c) 1998, 2004 The NetBSD Foundation, Inc.
      5        1.1    bouyer  * All rights reserved.
      6        1.1    bouyer  *
      7        1.1    bouyer  * This code is derived from software contributed to The NetBSD Foundation
      8        1.1    bouyer  * by Charles M. Hannum.
      9        1.1    bouyer  *
     10        1.1    bouyer  * Redistribution and use in source and binary forms, with or without
     11        1.1    bouyer  * modification, are permitted provided that the following conditions
     12        1.1    bouyer  * are met:
     13        1.1    bouyer  * 1. Redistributions of source code must retain the above copyright
     14        1.1    bouyer  *    notice, this list of conditions and the following disclaimer.
     15        1.1    bouyer  * 2. Redistributions in binary form must reproduce the above copyright
     16        1.1    bouyer  *    notice, this list of conditions and the following disclaimer in the
     17        1.1    bouyer  *    documentation and/or other materials provided with the distribution.
     18        1.1    bouyer  * 3. All advertising materials mentioning features or use of this software
     19        1.1    bouyer  *    must display the following acknowledgement:
     20        1.1    bouyer  *        This product includes software developed by the NetBSD
     21        1.1    bouyer  *        Foundation, Inc. and its contributors.
     22        1.1    bouyer  * 4. Neither the name of The NetBSD Foundation nor the names of its
     23        1.1    bouyer  *    contributors may be used to endorse or promote products derived
     24        1.1    bouyer  *    from this software without specific prior written permission.
     25        1.1    bouyer  *
     26        1.1    bouyer  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
     27        1.1    bouyer  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
     28        1.1    bouyer  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     29        1.1    bouyer  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
     30        1.1    bouyer  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
     31        1.1    bouyer  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
     32        1.1    bouyer  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
     33        1.1    bouyer  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
     34        1.1    bouyer  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
     35        1.1    bouyer  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
     36        1.1    bouyer  * POSSIBILITY OF SUCH DAMAGE.
     37        1.1    bouyer  */
     38        1.1    bouyer 
     39        1.1    bouyer /*
     40        1.1    bouyer  * Originally written by Julian Elischer (julian (at) tfs.com)
     41        1.1    bouyer  * for TRW Financial Systems for use under the MACH(2.5) operating system.
     42        1.1    bouyer  *
     43        1.1    bouyer  * TRW Financial Systems, in accordance with their agreement with Carnegie
     44        1.1    bouyer  * Mellon University, makes this software available to CMU to distribute
     45        1.1    bouyer  * or use in any manner that they see fit as long as this message is kept with
     46        1.1    bouyer  * the software. For this reason TFS also grants any other persons or
     47        1.1    bouyer  * organisations permission to use or modify this software.
     48        1.1    bouyer  *
     49        1.1    bouyer  * TFS supplies this software to be publicly redistributed
     50        1.1    bouyer  * on the understanding that TFS is not responsible for the correct
     51        1.1    bouyer  * functioning of this software in any circumstances.
     52        1.1    bouyer  *
     53        1.1    bouyer  * Ported to run under 386BSD by Julian Elischer (julian (at) tfs.com) Sept 1992
     54        1.1    bouyer  * major changes by Julian Elischer (julian (at) jules.dialix.oz.au) May 1993
     55        1.1    bouyer  *
     56        1.1    bouyer  * A lot of rewhacking done by mjacob (mjacob (at) nas.nasa.gov).
     57        1.1    bouyer  */
     58        1.5     lukem 
     59        1.5     lukem #include <sys/cdefs.h>
     60  1.23.12.1      tron __KERNEL_RCSID(0, "$NetBSD: st_scsi.c,v 1.23.12.1 2006/03/31 09:45:25 tron Exp $");
     61        1.1    bouyer 
     62        1.1    bouyer #include "opt_scsi.h"
     63        1.1    bouyer #include "rnd.h"
     64        1.1    bouyer 
     65        1.1    bouyer #include <sys/param.h>
     66        1.1    bouyer #include <sys/device.h>
     67        1.1    bouyer #include <sys/buf.h>
     68       1.16      yamt #include <sys/bufq.h>
     69        1.1    bouyer #include <sys/conf.h>
     70        1.1    bouyer #include <sys/kernel.h>
     71        1.2    bouyer #include <sys/systm.h>
     72        1.1    bouyer 
     73       1.15   mycroft #include <dev/scsipi/scsi_all.h>
     74       1.15   mycroft #include <dev/scsipi/scsi_tape.h>
     75        1.1    bouyer #include <dev/scsipi/stvar.h>
     76        1.1    bouyer 
     77       1.11   thorpej static int	st_scsibus_match(struct device *, struct cfdata *, void *);
     78       1.11   thorpej static void	st_scsibus_attach(struct device *, struct device *, void *);
     79       1.11   thorpej static int	st_scsibus_ops(struct st_softc *, int, int);
     80       1.11   thorpej static int	st_scsibus_read_block_limits(struct st_softc *, int);
     81       1.11   thorpej static int	st_scsibus_mode_sense(struct st_softc *, int);
     82       1.11   thorpej static int	st_scsibus_mode_select(struct st_softc *, int);
     83       1.11   thorpej static int	st_scsibus_cmprss(struct st_softc *, int, int);
     84        1.1    bouyer 
     85        1.9   thorpej CFATTACH_DECL(st_scsibus, sizeof(struct st_softc),
     86       1.10   thorpej     st_scsibus_match, st_scsibus_attach, stdetach, stactivate);
     87        1.1    bouyer 
     88       1.11   thorpej static const struct scsipi_inquiry_pattern st_scsibus_patterns[] = {
     89        1.1    bouyer 	{T_SEQUENTIAL, T_REMOV,
     90        1.1    bouyer 	 "",         "",                 ""},
     91        1.1    bouyer };
     92        1.1    bouyer 
     93       1.11   thorpej static int
     94       1.11   thorpej st_scsibus_match(struct device *parent, struct cfdata *match, void *aux)
     95        1.1    bouyer {
     96        1.1    bouyer 	struct scsipibus_attach_args *sa = aux;
     97        1.1    bouyer 	int priority;
     98        1.1    bouyer 
     99        1.2    bouyer 	if (scsipi_periph_bustype(sa->sa_periph) != SCSIPI_BUSTYPE_SCSI)
    100        1.2    bouyer 		return (0);
    101        1.2    bouyer 
    102        1.1    bouyer 	(void)scsipi_inqmatch(&sa->sa_inqbuf,
    103       1.22  christos 	    st_scsibus_patterns,
    104        1.1    bouyer 	    sizeof(st_scsibus_patterns)/sizeof(st_scsibus_patterns[0]),
    105        1.1    bouyer 	    sizeof(st_scsibus_patterns[0]), &priority);
    106        1.1    bouyer 	return (priority);
    107        1.2    bouyer }
    108        1.2    bouyer 
    109       1.11   thorpej static void
    110       1.11   thorpej st_scsibus_attach(struct device *parent, struct device *self, void *aux)
    111        1.2    bouyer {
    112  1.23.12.1      tron 	struct st_softc *st = device_private(self);
    113        1.2    bouyer 
    114        1.2    bouyer 	st->ops = st_scsibus_ops;
    115        1.2    bouyer 	stattach(parent, st, aux);
    116        1.2    bouyer }
    117        1.2    bouyer 
    118       1.11   thorpej static int
    119       1.11   thorpej st_scsibus_ops(struct st_softc *st, int op, int flags)
    120        1.2    bouyer {
    121        1.2    bouyer 	switch(op) {
    122        1.2    bouyer 	case ST_OPS_RBL:
    123        1.2    bouyer 		return st_scsibus_read_block_limits(st, flags);
    124        1.2    bouyer 	case ST_OPS_MODESENSE:
    125        1.2    bouyer 		return st_scsibus_mode_sense(st, flags);
    126        1.2    bouyer 	case ST_OPS_MODESELECT:
    127        1.2    bouyer 		return st_scsibus_mode_select(st, flags);
    128        1.2    bouyer 	case ST_OPS_CMPRSS_ON:
    129        1.2    bouyer 	case ST_OPS_CMPRSS_OFF:
    130        1.2    bouyer 		return st_scsibus_cmprss(st, flags,
    131        1.2    bouyer 		    (op == ST_OPS_CMPRSS_ON) ? 1 : 0);
    132        1.2    bouyer 	default:
    133        1.2    bouyer 		panic("st_scsibus_ops: invalid op");
    134        1.2    bouyer 		return 0; /* XXX to appease gcc */
    135        1.2    bouyer 	}
    136        1.2    bouyer 	/* NOTREACHED */
    137        1.2    bouyer }
    138        1.2    bouyer 
    139        1.2    bouyer /*
    140        1.2    bouyer  * Ask the drive what it's min and max blk sizes are.
    141        1.2    bouyer  */
    142       1.11   thorpej static int
    143       1.11   thorpej st_scsibus_read_block_limits(struct st_softc *st, int flags)
    144        1.2    bouyer {
    145        1.2    bouyer 	struct scsi_block_limits cmd;
    146        1.2    bouyer 	struct scsi_block_limits_data block_limits;
    147        1.2    bouyer 	struct scsipi_periph *periph = st->sc_periph;
    148        1.2    bouyer 	int error;
    149        1.2    bouyer 
    150        1.2    bouyer 	/*
    151        1.2    bouyer 	 * do a 'Read Block Limits'
    152        1.2    bouyer 	 */
    153        1.3   thorpej 	memset(&cmd, 0, sizeof(cmd));
    154        1.2    bouyer 	cmd.opcode = READ_BLOCK_LIMITS;
    155        1.2    bouyer 
    156        1.2    bouyer 	/*
    157        1.2    bouyer 	 * do the command, update the global values
    158        1.2    bouyer 	 */
    159       1.14   mycroft 	error = scsipi_command(periph, (void *)&cmd, sizeof(cmd),
    160       1.14   mycroft 	    (void *)&block_limits, sizeof(block_limits),
    161        1.2    bouyer 	    ST_RETRIES, ST_CTL_TIME, NULL,
    162        1.2    bouyer 	    flags | XS_CTL_DATA_IN | XS_CTL_DATA_ONSTACK);
    163        1.2    bouyer 	if (error)
    164        1.2    bouyer 		return (error);
    165        1.2    bouyer 
    166        1.2    bouyer 	st->blkmin = _2btol(block_limits.min_length);
    167        1.2    bouyer 	st->blkmax = _3btol(block_limits.max_length);
    168        1.2    bouyer 
    169        1.2    bouyer 	SC_DEBUG(periph, SCSIPI_DB3,
    170        1.2    bouyer 	    ("(%d <= blksize <= %d)\n", st->blkmin, st->blkmax));
    171        1.2    bouyer 	return (0);
    172        1.2    bouyer }
    173        1.2    bouyer 
    174        1.2    bouyer /*
    175        1.2    bouyer  * Get the scsi driver to send a full inquiry to the
    176        1.2    bouyer  * device and use the results to fill out the global
    177        1.2    bouyer  * parameter structure.
    178        1.2    bouyer  *
    179        1.2    bouyer  * called from:
    180        1.2    bouyer  * attach
    181        1.2    bouyer  * open
    182        1.2    bouyer  * ioctl (to reset original blksize)
    183        1.2    bouyer  */
    184       1.11   thorpej static int
    185       1.11   thorpej st_scsibus_mode_sense(struct st_softc *st, int flags)
    186        1.2    bouyer {
    187       1.19   reinoud 	u_int scsipi_sense_len;
    188        1.2    bouyer 	int error;
    189        1.2    bouyer 	struct scsipi_sense {
    190       1.20   thorpej 		struct scsi_mode_parameter_header_6 header;
    191       1.20   thorpej 		struct scsi_general_block_descriptor blk_desc;
    192       1.19   reinoud 		u_char sense_data[MAX_PAGE_0_SIZE];
    193        1.2    bouyer 	} scsipi_sense;
    194        1.2    bouyer 	struct scsipi_periph *periph = st->sc_periph;
    195        1.2    bouyer 
    196        1.2    bouyer 	scsipi_sense_len = 12 + st->page_0_size;
    197        1.2    bouyer 
    198        1.2    bouyer 	/*
    199        1.2    bouyer 	 * Set up a mode sense
    200        1.2    bouyer 	 * We don't need the results. Just print them for our interest's sake,
    201        1.2    bouyer 	 * if asked, or if we need it as a template for the mode select store
    202        1.2    bouyer 	 * it away.
    203        1.2    bouyer 	 */
    204       1.20   thorpej 	error = scsipi_mode_sense(st->sc_periph, 0, SMS_PCTRL_CURRENT,
    205        1.2    bouyer 	    &scsipi_sense.header, scsipi_sense_len, flags | XS_CTL_DATA_ONSTACK,
    206        1.2    bouyer 	    ST_RETRIES, ST_CTL_TIME);
    207        1.2    bouyer 	if (error)
    208        1.2    bouyer 		return (error);
    209        1.2    bouyer 
    210        1.2    bouyer 	st->numblks = _3btol(scsipi_sense.blk_desc.nblocks);
    211        1.2    bouyer 	st->media_blksize = _3btol(scsipi_sense.blk_desc.blklen);
    212        1.2    bouyer 	st->media_density = scsipi_sense.blk_desc.density;
    213        1.2    bouyer 	if (scsipi_sense.header.dev_spec & SMH_DSP_WRITE_PROT)
    214        1.2    bouyer 		st->flags |= ST_READONLY;
    215        1.2    bouyer 	else
    216        1.2    bouyer 		st->flags &= ~ST_READONLY;
    217        1.2    bouyer 	SC_DEBUG(periph, SCSIPI_DB3,
    218        1.2    bouyer 	    ("density code %d, %d-byte blocks, write-%s, ",
    219        1.2    bouyer 	    st->media_density, st->media_blksize,
    220        1.2    bouyer 	    st->flags & ST_READONLY ? "protected" : "enabled"));
    221        1.2    bouyer 	SC_DEBUG(periph, SCSIPI_DB3,
    222        1.2    bouyer 	    ("%sbuffered\n",
    223        1.2    bouyer 	    scsipi_sense.header.dev_spec & SMH_DSP_BUFF_MODE ? "" : "un"));
    224        1.2    bouyer 	if (st->page_0_size)
    225        1.4   thorpej 		memcpy(st->sense_data, scsipi_sense.sense_data,
    226        1.2    bouyer 		    st->page_0_size);
    227        1.2    bouyer 	periph->periph_flags |= PERIPH_MEDIA_LOADED;
    228        1.2    bouyer 	return (0);
    229        1.2    bouyer }
    230        1.2    bouyer 
    231        1.2    bouyer /*
    232        1.2    bouyer  * Send a filled out parameter structure to the drive to
    233        1.2    bouyer  * set it into the desire modes etc.
    234        1.2    bouyer  */
    235       1.11   thorpej static int
    236       1.11   thorpej st_scsibus_mode_select(struct st_softc *st, int flags)
    237        1.2    bouyer {
    238       1.19   reinoud 	u_int scsi_select_len;
    239        1.2    bouyer 	struct scsi_select {
    240       1.20   thorpej 		struct scsi_mode_parameter_header_6 header;
    241       1.20   thorpej 		struct scsi_general_block_descriptor blk_desc;
    242       1.19   reinoud 		u_char sense_data[MAX_PAGE_0_SIZE];
    243        1.2    bouyer 	} scsi_select;
    244        1.2    bouyer 	struct scsipi_periph *periph = st->sc_periph;
    245        1.2    bouyer 
    246        1.2    bouyer 	scsi_select_len = 12 + st->page_0_size;
    247        1.2    bouyer 
    248        1.2    bouyer 	/*
    249        1.2    bouyer 	 * This quirk deals with drives that have only one valid mode
    250        1.2    bouyer 	 * and think this gives them license to reject all mode selects,
    251        1.2    bouyer 	 * even if the selected mode is the one that is supported.
    252        1.2    bouyer 	 */
    253        1.2    bouyer 	if (st->quirks & ST_Q_UNIMODAL) {
    254        1.2    bouyer 		SC_DEBUG(periph, SCSIPI_DB3,
    255        1.2    bouyer 		    ("not setting density 0x%x blksize 0x%x\n",
    256        1.2    bouyer 		    st->density, st->blksize));
    257        1.2    bouyer 		return (0);
    258        1.2    bouyer 	}
    259        1.2    bouyer 
    260        1.2    bouyer 	/*
    261        1.2    bouyer 	 * Set up for a mode select
    262        1.2    bouyer 	 */
    263        1.3   thorpej 	memset(&scsi_select, 0, scsi_select_len);
    264       1.20   thorpej 	scsi_select.header.blk_desc_len = sizeof(struct scsi_general_block_descriptor);
    265        1.2    bouyer 	scsi_select.header.dev_spec &= ~SMH_DSP_BUFF_MODE;
    266        1.2    bouyer 	scsi_select.blk_desc.density = st->density;
    267        1.2    bouyer 	if (st->flags & ST_DONTBUFFER)
    268        1.2    bouyer 		scsi_select.header.dev_spec |= SMH_DSP_BUFF_MODE_OFF;
    269        1.2    bouyer 	else
    270        1.2    bouyer 		scsi_select.header.dev_spec |= SMH_DSP_BUFF_MODE_ON;
    271        1.2    bouyer 	if (st->flags & ST_FIXEDBLOCKS)
    272        1.2    bouyer 		_lto3b(st->blksize, scsi_select.blk_desc.blklen);
    273        1.2    bouyer 	if (st->page_0_size)
    274        1.4   thorpej 		memcpy(scsi_select.sense_data, st->sense_data, st->page_0_size);
    275        1.2    bouyer 
    276        1.2    bouyer 	/*
    277        1.2    bouyer 	 * do the command
    278        1.2    bouyer 	 */
    279       1.21     perry 	return scsipi_mode_select(periph, 0, &scsi_select.header,
    280        1.2    bouyer 	    scsi_select_len, flags | XS_CTL_DATA_ONSTACK,
    281        1.2    bouyer 	    ST_RETRIES, ST_CTL_TIME);
    282        1.2    bouyer }
    283        1.2    bouyer 
    284       1.11   thorpej static int
    285       1.11   thorpej st_scsibus_cmprss(struct st_softc *st, int flags, int onoff)
    286        1.2    bouyer {
    287       1.19   reinoud 	u_int scsi_dlen;
    288        1.2    bouyer 	int byte2, page;
    289        1.2    bouyer 	struct scsi_select {
    290       1.20   thorpej 		struct scsi_mode_parameter_header_6 header;
    291       1.20   thorpej 		struct scsi_general_block_descriptor blk_desc;
    292       1.19   reinoud 		u_char pdata[MAX(sizeof(struct scsi_tape_dev_conf_page),
    293        1.2    bouyer 		    sizeof(struct scsi_tape_dev_compression_page))];
    294        1.2    bouyer 	} scsi_pdata;
    295        1.2    bouyer 	struct scsi_tape_dev_conf_page *ptr;
    296        1.2    bouyer 	struct scsi_tape_dev_compression_page *cptr;
    297        1.2    bouyer 	struct scsipi_periph *periph = st->sc_periph;
    298        1.2    bouyer 	int error, ison;
    299        1.2    bouyer 
    300        1.2    bouyer 	scsi_dlen = sizeof(scsi_pdata);
    301       1.21     perry 	/*
    302        1.2    bouyer 	 * Do DATA COMPRESSION page first.
    303        1.2    bouyer 	 */
    304       1.20   thorpej 	page = SMS_PCTRL_CURRENT | 0xf;
    305        1.2    bouyer 	byte2 = 0;
    306        1.2    bouyer 
    307        1.2    bouyer 	/*
    308        1.2    bouyer 	 * Do the MODE SENSE command...
    309        1.2    bouyer 	 */
    310        1.2    bouyer again:
    311        1.3   thorpej 	memset(&scsi_pdata, 0, scsi_dlen);
    312        1.2    bouyer 	error = scsipi_mode_sense(periph, byte2, page,
    313        1.2    bouyer 	    &scsi_pdata.header, scsi_dlen, flags | XS_CTL_DATA_ONSTACK,
    314        1.2    bouyer 	    ST_RETRIES, ST_CTL_TIME);
    315        1.2    bouyer 
    316        1.2    bouyer 	if (error) {
    317        1.2    bouyer 		if (byte2 != SMS_DBD) {
    318        1.2    bouyer 			byte2 = SMS_DBD;
    319        1.2    bouyer 			goto again;
    320        1.2    bouyer 		}
    321        1.2    bouyer 		/*
    322        1.2    bouyer 		 * Try a different page?
    323        1.2    bouyer 		 */
    324       1.20   thorpej 		if (page == (SMS_PCTRL_CURRENT | 0xf)) {
    325       1.20   thorpej 			page = SMS_PCTRL_CURRENT | 0x10;
    326        1.2    bouyer 			byte2 = 0;
    327        1.2    bouyer 			goto again;
    328        1.2    bouyer 		}
    329        1.2    bouyer 		return (error);
    330        1.2    bouyer 	}
    331        1.2    bouyer 
    332        1.2    bouyer 	if (scsi_pdata.header.blk_desc_len)
    333        1.2    bouyer 		ptr = (struct scsi_tape_dev_conf_page *) scsi_pdata.pdata;
    334        1.2    bouyer 	else
    335        1.2    bouyer 		ptr = (struct scsi_tape_dev_conf_page *) &scsi_pdata.blk_desc;
    336        1.2    bouyer 
    337       1.20   thorpej 	if ((page & SMS_PAGE_MASK) == 0xf) {
    338        1.2    bouyer 		cptr = (struct scsi_tape_dev_compression_page *) ptr;
    339        1.2    bouyer 		ison = (cptr->dce_dcc & DCP_DCE) != 0;
    340        1.2    bouyer 		if (onoff)
    341        1.2    bouyer 			cptr->dce_dcc |= DCP_DCE;
    342        1.2    bouyer 		else
    343        1.2    bouyer 			cptr->dce_dcc &= ~DCP_DCE;
    344        1.2    bouyer 		cptr->pagecode &= ~0x80;
    345        1.2    bouyer 	} else {
    346        1.2    bouyer 		ison =  (ptr->sel_comp_alg != 0);
    347        1.2    bouyer 		if (onoff)
    348        1.2    bouyer 			ptr->sel_comp_alg = 1;
    349        1.2    bouyer 		else
    350        1.2    bouyer 			ptr->sel_comp_alg = 0;
    351        1.2    bouyer 		ptr->pagecode &= ~0x80;
    352        1.2    bouyer 		ptr->byte2 = 0;
    353        1.2    bouyer 		ptr->active_partition = 0;
    354        1.2    bouyer 		ptr->wb_full_ratio = 0;
    355        1.2    bouyer 		ptr->rb_empty_ratio = 0;
    356        1.2    bouyer 		ptr->byte8 &= ~0x30;
    357        1.2    bouyer 		ptr->gap_size = 0;
    358        1.2    bouyer 		ptr->byte10 &= ~0xe7;
    359        1.2    bouyer 		ptr->ew_bufsize[0] = 0;
    360        1.2    bouyer 		ptr->ew_bufsize[1] = 0;
    361        1.2    bouyer 		ptr->ew_bufsize[2] = 0;
    362        1.2    bouyer 		ptr->reserved = 0;
    363        1.2    bouyer 	}
    364        1.2    bouyer 	/*
    365        1.2    bouyer 	 * There might be a virtue in actually doing the MODE SELECTS,
    366        1.2    bouyer 	 * but let's not clog the bus over it.
    367        1.2    bouyer 	 */
    368        1.2    bouyer 	if (onoff == ison)
    369        1.2    bouyer 		return (0);
    370        1.2    bouyer 
    371        1.2    bouyer 	/*
    372        1.2    bouyer 	 * Set up for a mode select
    373        1.2    bouyer 	 */
    374        1.2    bouyer 
    375        1.2    bouyer 	scsi_pdata.header.data_length = 0;
    376        1.2    bouyer 	scsi_pdata.header.medium_type = 0;
    377        1.2    bouyer 	if ((st->flags & ST_DONTBUFFER) == 0)
    378        1.2    bouyer 		scsi_pdata.header.dev_spec = SMH_DSP_BUFF_MODE_ON;
    379        1.2    bouyer 	else
    380        1.2    bouyer 		scsi_pdata.header.dev_spec = 0;
    381        1.2    bouyer 
    382        1.2    bouyer 	if (scsi_pdata.header.blk_desc_len) {
    383        1.2    bouyer 		scsi_pdata.blk_desc.density = 0;
    384        1.2    bouyer 		scsi_pdata.blk_desc.nblocks[0] = 0;
    385        1.2    bouyer 		scsi_pdata.blk_desc.nblocks[1] = 0;
    386        1.2    bouyer 		scsi_pdata.blk_desc.nblocks[2] = 0;
    387        1.2    bouyer 	}
    388        1.2    bouyer 
    389        1.2    bouyer 	/*
    390        1.2    bouyer 	 * Do the command
    391        1.2    bouyer 	 */
    392        1.2    bouyer 	error = scsipi_mode_select(periph, SMS_PF, &scsi_pdata.header,
    393        1.2    bouyer 	    scsi_dlen, flags | XS_CTL_DATA_ONSTACK, ST_RETRIES, ST_CTL_TIME);
    394        1.2    bouyer 
    395       1.20   thorpej 	if (error && (page & SMS_PAGE_MASK) == 0xf) {
    396        1.2    bouyer 		/*
    397        1.2    bouyer 		 * Try DEVICE CONFIGURATION page.
    398        1.2    bouyer 		 */
    399       1.20   thorpej 		page = SMS_PCTRL_CURRENT | 0x10;
    400        1.2    bouyer 		goto again;
    401        1.2    bouyer 	}
    402        1.2    bouyer 	return (error);
    403        1.1    bouyer }
    404