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st_scsi.c revision 1.25
      1  1.25  christos /*	$NetBSD: st_scsi.c,v 1.25 2006/10/12 01:31:58 christos 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  1.25  christos __KERNEL_RCSID(0, "$NetBSD: st_scsi.c,v 1.25 2006/10/12 01:31:58 christos 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  1.25  christos st_scsibus_match(struct device *parent __unused, struct cfdata *match __unused,
     95  1.25  christos     void *aux)
     96   1.1    bouyer {
     97   1.1    bouyer 	struct scsipibus_attach_args *sa = aux;
     98   1.1    bouyer 	int priority;
     99   1.1    bouyer 
    100   1.2    bouyer 	if (scsipi_periph_bustype(sa->sa_periph) != SCSIPI_BUSTYPE_SCSI)
    101   1.2    bouyer 		return (0);
    102   1.2    bouyer 
    103   1.1    bouyer 	(void)scsipi_inqmatch(&sa->sa_inqbuf,
    104  1.22  christos 	    st_scsibus_patterns,
    105   1.1    bouyer 	    sizeof(st_scsibus_patterns)/sizeof(st_scsibus_patterns[0]),
    106   1.1    bouyer 	    sizeof(st_scsibus_patterns[0]), &priority);
    107   1.1    bouyer 	return (priority);
    108   1.2    bouyer }
    109   1.2    bouyer 
    110  1.11   thorpej static void
    111  1.11   thorpej st_scsibus_attach(struct device *parent, struct device *self, void *aux)
    112   1.2    bouyer {
    113  1.24   thorpej 	struct st_softc *st = device_private(self);
    114   1.2    bouyer 
    115   1.2    bouyer 	st->ops = st_scsibus_ops;
    116   1.2    bouyer 	stattach(parent, st, aux);
    117   1.2    bouyer }
    118   1.2    bouyer 
    119  1.11   thorpej static int
    120  1.11   thorpej st_scsibus_ops(struct st_softc *st, int op, int flags)
    121   1.2    bouyer {
    122   1.2    bouyer 	switch(op) {
    123   1.2    bouyer 	case ST_OPS_RBL:
    124   1.2    bouyer 		return st_scsibus_read_block_limits(st, flags);
    125   1.2    bouyer 	case ST_OPS_MODESENSE:
    126   1.2    bouyer 		return st_scsibus_mode_sense(st, flags);
    127   1.2    bouyer 	case ST_OPS_MODESELECT:
    128   1.2    bouyer 		return st_scsibus_mode_select(st, flags);
    129   1.2    bouyer 	case ST_OPS_CMPRSS_ON:
    130   1.2    bouyer 	case ST_OPS_CMPRSS_OFF:
    131   1.2    bouyer 		return st_scsibus_cmprss(st, flags,
    132   1.2    bouyer 		    (op == ST_OPS_CMPRSS_ON) ? 1 : 0);
    133   1.2    bouyer 	default:
    134   1.2    bouyer 		panic("st_scsibus_ops: invalid op");
    135   1.2    bouyer 		return 0; /* XXX to appease gcc */
    136   1.2    bouyer 	}
    137   1.2    bouyer 	/* NOTREACHED */
    138   1.2    bouyer }
    139   1.2    bouyer 
    140   1.2    bouyer /*
    141   1.2    bouyer  * Ask the drive what it's min and max blk sizes are.
    142   1.2    bouyer  */
    143  1.11   thorpej static int
    144  1.11   thorpej st_scsibus_read_block_limits(struct st_softc *st, int flags)
    145   1.2    bouyer {
    146   1.2    bouyer 	struct scsi_block_limits cmd;
    147   1.2    bouyer 	struct scsi_block_limits_data block_limits;
    148   1.2    bouyer 	struct scsipi_periph *periph = st->sc_periph;
    149   1.2    bouyer 	int error;
    150   1.2    bouyer 
    151   1.2    bouyer 	/*
    152   1.2    bouyer 	 * do a 'Read Block Limits'
    153   1.2    bouyer 	 */
    154   1.3   thorpej 	memset(&cmd, 0, sizeof(cmd));
    155   1.2    bouyer 	cmd.opcode = READ_BLOCK_LIMITS;
    156   1.2    bouyer 
    157   1.2    bouyer 	/*
    158   1.2    bouyer 	 * do the command, update the global values
    159   1.2    bouyer 	 */
    160  1.14   mycroft 	error = scsipi_command(periph, (void *)&cmd, sizeof(cmd),
    161  1.14   mycroft 	    (void *)&block_limits, sizeof(block_limits),
    162   1.2    bouyer 	    ST_RETRIES, ST_CTL_TIME, NULL,
    163   1.2    bouyer 	    flags | XS_CTL_DATA_IN | XS_CTL_DATA_ONSTACK);
    164   1.2    bouyer 	if (error)
    165   1.2    bouyer 		return (error);
    166   1.2    bouyer 
    167   1.2    bouyer 	st->blkmin = _2btol(block_limits.min_length);
    168   1.2    bouyer 	st->blkmax = _3btol(block_limits.max_length);
    169   1.2    bouyer 
    170   1.2    bouyer 	SC_DEBUG(periph, SCSIPI_DB3,
    171   1.2    bouyer 	    ("(%d <= blksize <= %d)\n", st->blkmin, st->blkmax));
    172   1.2    bouyer 	return (0);
    173   1.2    bouyer }
    174   1.2    bouyer 
    175   1.2    bouyer /*
    176   1.2    bouyer  * Get the scsi driver to send a full inquiry to the
    177   1.2    bouyer  * device and use the results to fill out the global
    178   1.2    bouyer  * parameter structure.
    179   1.2    bouyer  *
    180   1.2    bouyer  * called from:
    181   1.2    bouyer  * attach
    182   1.2    bouyer  * open
    183   1.2    bouyer  * ioctl (to reset original blksize)
    184   1.2    bouyer  */
    185  1.11   thorpej static int
    186  1.11   thorpej st_scsibus_mode_sense(struct st_softc *st, int flags)
    187   1.2    bouyer {
    188  1.19   reinoud 	u_int scsipi_sense_len;
    189   1.2    bouyer 	int error;
    190   1.2    bouyer 	struct scsipi_sense {
    191  1.20   thorpej 		struct scsi_mode_parameter_header_6 header;
    192  1.20   thorpej 		struct scsi_general_block_descriptor blk_desc;
    193  1.19   reinoud 		u_char sense_data[MAX_PAGE_0_SIZE];
    194   1.2    bouyer 	} scsipi_sense;
    195   1.2    bouyer 	struct scsipi_periph *periph = st->sc_periph;
    196   1.2    bouyer 
    197   1.2    bouyer 	scsipi_sense_len = 12 + st->page_0_size;
    198   1.2    bouyer 
    199   1.2    bouyer 	/*
    200   1.2    bouyer 	 * Set up a mode sense
    201   1.2    bouyer 	 * We don't need the results. Just print them for our interest's sake,
    202   1.2    bouyer 	 * if asked, or if we need it as a template for the mode select store
    203   1.2    bouyer 	 * it away.
    204   1.2    bouyer 	 */
    205  1.20   thorpej 	error = scsipi_mode_sense(st->sc_periph, 0, SMS_PCTRL_CURRENT,
    206   1.2    bouyer 	    &scsipi_sense.header, scsipi_sense_len, flags | XS_CTL_DATA_ONSTACK,
    207   1.2    bouyer 	    ST_RETRIES, ST_CTL_TIME);
    208   1.2    bouyer 	if (error)
    209   1.2    bouyer 		return (error);
    210   1.2    bouyer 
    211   1.2    bouyer 	st->numblks = _3btol(scsipi_sense.blk_desc.nblocks);
    212   1.2    bouyer 	st->media_blksize = _3btol(scsipi_sense.blk_desc.blklen);
    213   1.2    bouyer 	st->media_density = scsipi_sense.blk_desc.density;
    214   1.2    bouyer 	if (scsipi_sense.header.dev_spec & SMH_DSP_WRITE_PROT)
    215   1.2    bouyer 		st->flags |= ST_READONLY;
    216   1.2    bouyer 	else
    217   1.2    bouyer 		st->flags &= ~ST_READONLY;
    218   1.2    bouyer 	SC_DEBUG(periph, SCSIPI_DB3,
    219   1.2    bouyer 	    ("density code %d, %d-byte blocks, write-%s, ",
    220   1.2    bouyer 	    st->media_density, st->media_blksize,
    221   1.2    bouyer 	    st->flags & ST_READONLY ? "protected" : "enabled"));
    222   1.2    bouyer 	SC_DEBUG(periph, SCSIPI_DB3,
    223   1.2    bouyer 	    ("%sbuffered\n",
    224   1.2    bouyer 	    scsipi_sense.header.dev_spec & SMH_DSP_BUFF_MODE ? "" : "un"));
    225   1.2    bouyer 	if (st->page_0_size)
    226   1.4   thorpej 		memcpy(st->sense_data, scsipi_sense.sense_data,
    227   1.2    bouyer 		    st->page_0_size);
    228   1.2    bouyer 	periph->periph_flags |= PERIPH_MEDIA_LOADED;
    229   1.2    bouyer 	return (0);
    230   1.2    bouyer }
    231   1.2    bouyer 
    232   1.2    bouyer /*
    233   1.2    bouyer  * Send a filled out parameter structure to the drive to
    234   1.2    bouyer  * set it into the desire modes etc.
    235   1.2    bouyer  */
    236  1.11   thorpej static int
    237  1.11   thorpej st_scsibus_mode_select(struct st_softc *st, int flags)
    238   1.2    bouyer {
    239  1.19   reinoud 	u_int scsi_select_len;
    240   1.2    bouyer 	struct scsi_select {
    241  1.20   thorpej 		struct scsi_mode_parameter_header_6 header;
    242  1.20   thorpej 		struct scsi_general_block_descriptor blk_desc;
    243  1.19   reinoud 		u_char sense_data[MAX_PAGE_0_SIZE];
    244   1.2    bouyer 	} scsi_select;
    245   1.2    bouyer 	struct scsipi_periph *periph = st->sc_periph;
    246   1.2    bouyer 
    247   1.2    bouyer 	scsi_select_len = 12 + st->page_0_size;
    248   1.2    bouyer 
    249   1.2    bouyer 	/*
    250   1.2    bouyer 	 * This quirk deals with drives that have only one valid mode
    251   1.2    bouyer 	 * and think this gives them license to reject all mode selects,
    252   1.2    bouyer 	 * even if the selected mode is the one that is supported.
    253   1.2    bouyer 	 */
    254   1.2    bouyer 	if (st->quirks & ST_Q_UNIMODAL) {
    255   1.2    bouyer 		SC_DEBUG(periph, SCSIPI_DB3,
    256   1.2    bouyer 		    ("not setting density 0x%x blksize 0x%x\n",
    257   1.2    bouyer 		    st->density, st->blksize));
    258   1.2    bouyer 		return (0);
    259   1.2    bouyer 	}
    260   1.2    bouyer 
    261   1.2    bouyer 	/*
    262   1.2    bouyer 	 * Set up for a mode select
    263   1.2    bouyer 	 */
    264   1.3   thorpej 	memset(&scsi_select, 0, scsi_select_len);
    265  1.20   thorpej 	scsi_select.header.blk_desc_len = sizeof(struct scsi_general_block_descriptor);
    266   1.2    bouyer 	scsi_select.header.dev_spec &= ~SMH_DSP_BUFF_MODE;
    267   1.2    bouyer 	scsi_select.blk_desc.density = st->density;
    268   1.2    bouyer 	if (st->flags & ST_DONTBUFFER)
    269   1.2    bouyer 		scsi_select.header.dev_spec |= SMH_DSP_BUFF_MODE_OFF;
    270   1.2    bouyer 	else
    271   1.2    bouyer 		scsi_select.header.dev_spec |= SMH_DSP_BUFF_MODE_ON;
    272   1.2    bouyer 	if (st->flags & ST_FIXEDBLOCKS)
    273   1.2    bouyer 		_lto3b(st->blksize, scsi_select.blk_desc.blklen);
    274   1.2    bouyer 	if (st->page_0_size)
    275   1.4   thorpej 		memcpy(scsi_select.sense_data, st->sense_data, st->page_0_size);
    276   1.2    bouyer 
    277   1.2    bouyer 	/*
    278   1.2    bouyer 	 * do the command
    279   1.2    bouyer 	 */
    280  1.21     perry 	return scsipi_mode_select(periph, 0, &scsi_select.header,
    281   1.2    bouyer 	    scsi_select_len, flags | XS_CTL_DATA_ONSTACK,
    282   1.2    bouyer 	    ST_RETRIES, ST_CTL_TIME);
    283   1.2    bouyer }
    284   1.2    bouyer 
    285  1.11   thorpej static int
    286  1.11   thorpej st_scsibus_cmprss(struct st_softc *st, int flags, int onoff)
    287   1.2    bouyer {
    288  1.19   reinoud 	u_int scsi_dlen;
    289   1.2    bouyer 	int byte2, page;
    290   1.2    bouyer 	struct scsi_select {
    291  1.20   thorpej 		struct scsi_mode_parameter_header_6 header;
    292  1.20   thorpej 		struct scsi_general_block_descriptor blk_desc;
    293  1.19   reinoud 		u_char pdata[MAX(sizeof(struct scsi_tape_dev_conf_page),
    294   1.2    bouyer 		    sizeof(struct scsi_tape_dev_compression_page))];
    295   1.2    bouyer 	} scsi_pdata;
    296   1.2    bouyer 	struct scsi_tape_dev_conf_page *ptr;
    297   1.2    bouyer 	struct scsi_tape_dev_compression_page *cptr;
    298   1.2    bouyer 	struct scsipi_periph *periph = st->sc_periph;
    299   1.2    bouyer 	int error, ison;
    300   1.2    bouyer 
    301   1.2    bouyer 	scsi_dlen = sizeof(scsi_pdata);
    302  1.21     perry 	/*
    303   1.2    bouyer 	 * Do DATA COMPRESSION page first.
    304   1.2    bouyer 	 */
    305  1.20   thorpej 	page = SMS_PCTRL_CURRENT | 0xf;
    306   1.2    bouyer 	byte2 = 0;
    307   1.2    bouyer 
    308   1.2    bouyer 	/*
    309   1.2    bouyer 	 * Do the MODE SENSE command...
    310   1.2    bouyer 	 */
    311   1.2    bouyer again:
    312   1.3   thorpej 	memset(&scsi_pdata, 0, scsi_dlen);
    313   1.2    bouyer 	error = scsipi_mode_sense(periph, byte2, page,
    314   1.2    bouyer 	    &scsi_pdata.header, scsi_dlen, flags | XS_CTL_DATA_ONSTACK,
    315   1.2    bouyer 	    ST_RETRIES, ST_CTL_TIME);
    316   1.2    bouyer 
    317   1.2    bouyer 	if (error) {
    318   1.2    bouyer 		if (byte2 != SMS_DBD) {
    319   1.2    bouyer 			byte2 = SMS_DBD;
    320   1.2    bouyer 			goto again;
    321   1.2    bouyer 		}
    322   1.2    bouyer 		/*
    323   1.2    bouyer 		 * Try a different page?
    324   1.2    bouyer 		 */
    325  1.20   thorpej 		if (page == (SMS_PCTRL_CURRENT | 0xf)) {
    326  1.20   thorpej 			page = SMS_PCTRL_CURRENT | 0x10;
    327   1.2    bouyer 			byte2 = 0;
    328   1.2    bouyer 			goto again;
    329   1.2    bouyer 		}
    330   1.2    bouyer 		return (error);
    331   1.2    bouyer 	}
    332   1.2    bouyer 
    333   1.2    bouyer 	if (scsi_pdata.header.blk_desc_len)
    334   1.2    bouyer 		ptr = (struct scsi_tape_dev_conf_page *) scsi_pdata.pdata;
    335   1.2    bouyer 	else
    336   1.2    bouyer 		ptr = (struct scsi_tape_dev_conf_page *) &scsi_pdata.blk_desc;
    337   1.2    bouyer 
    338  1.20   thorpej 	if ((page & SMS_PAGE_MASK) == 0xf) {
    339   1.2    bouyer 		cptr = (struct scsi_tape_dev_compression_page *) ptr;
    340   1.2    bouyer 		ison = (cptr->dce_dcc & DCP_DCE) != 0;
    341   1.2    bouyer 		if (onoff)
    342   1.2    bouyer 			cptr->dce_dcc |= DCP_DCE;
    343   1.2    bouyer 		else
    344   1.2    bouyer 			cptr->dce_dcc &= ~DCP_DCE;
    345   1.2    bouyer 		cptr->pagecode &= ~0x80;
    346   1.2    bouyer 	} else {
    347   1.2    bouyer 		ison =  (ptr->sel_comp_alg != 0);
    348   1.2    bouyer 		if (onoff)
    349   1.2    bouyer 			ptr->sel_comp_alg = 1;
    350   1.2    bouyer 		else
    351   1.2    bouyer 			ptr->sel_comp_alg = 0;
    352   1.2    bouyer 		ptr->pagecode &= ~0x80;
    353   1.2    bouyer 		ptr->byte2 = 0;
    354   1.2    bouyer 		ptr->active_partition = 0;
    355   1.2    bouyer 		ptr->wb_full_ratio = 0;
    356   1.2    bouyer 		ptr->rb_empty_ratio = 0;
    357   1.2    bouyer 		ptr->byte8 &= ~0x30;
    358   1.2    bouyer 		ptr->gap_size = 0;
    359   1.2    bouyer 		ptr->byte10 &= ~0xe7;
    360   1.2    bouyer 		ptr->ew_bufsize[0] = 0;
    361   1.2    bouyer 		ptr->ew_bufsize[1] = 0;
    362   1.2    bouyer 		ptr->ew_bufsize[2] = 0;
    363   1.2    bouyer 		ptr->reserved = 0;
    364   1.2    bouyer 	}
    365   1.2    bouyer 	/*
    366   1.2    bouyer 	 * There might be a virtue in actually doing the MODE SELECTS,
    367   1.2    bouyer 	 * but let's not clog the bus over it.
    368   1.2    bouyer 	 */
    369   1.2    bouyer 	if (onoff == ison)
    370   1.2    bouyer 		return (0);
    371   1.2    bouyer 
    372   1.2    bouyer 	/*
    373   1.2    bouyer 	 * Set up for a mode select
    374   1.2    bouyer 	 */
    375   1.2    bouyer 
    376   1.2    bouyer 	scsi_pdata.header.data_length = 0;
    377   1.2    bouyer 	scsi_pdata.header.medium_type = 0;
    378   1.2    bouyer 	if ((st->flags & ST_DONTBUFFER) == 0)
    379   1.2    bouyer 		scsi_pdata.header.dev_spec = SMH_DSP_BUFF_MODE_ON;
    380   1.2    bouyer 	else
    381   1.2    bouyer 		scsi_pdata.header.dev_spec = 0;
    382   1.2    bouyer 
    383   1.2    bouyer 	if (scsi_pdata.header.blk_desc_len) {
    384   1.2    bouyer 		scsi_pdata.blk_desc.density = 0;
    385   1.2    bouyer 		scsi_pdata.blk_desc.nblocks[0] = 0;
    386   1.2    bouyer 		scsi_pdata.blk_desc.nblocks[1] = 0;
    387   1.2    bouyer 		scsi_pdata.blk_desc.nblocks[2] = 0;
    388   1.2    bouyer 	}
    389   1.2    bouyer 
    390   1.2    bouyer 	/*
    391   1.2    bouyer 	 * Do the command
    392   1.2    bouyer 	 */
    393   1.2    bouyer 	error = scsipi_mode_select(periph, SMS_PF, &scsi_pdata.header,
    394   1.2    bouyer 	    scsi_dlen, flags | XS_CTL_DATA_ONSTACK, ST_RETRIES, ST_CTL_TIME);
    395   1.2    bouyer 
    396  1.20   thorpej 	if (error && (page & SMS_PAGE_MASK) == 0xf) {
    397   1.2    bouyer 		/*
    398   1.2    bouyer 		 * Try DEVICE CONFIGURATION page.
    399   1.2    bouyer 		 */
    400  1.20   thorpej 		page = SMS_PCTRL_CURRENT | 0x10;
    401   1.2    bouyer 		goto again;
    402   1.2    bouyer 	}
    403   1.2    bouyer 	return (error);
    404   1.1    bouyer }
    405