text: /*
   * scsi_scan.c
   *
   * Copyright (C) 2000 Eric Youngdale,
   * Copyright (C) 2002 Patrick Mansfield
   *
   * The general scanning/probing algorithm is as follows, exceptions are
   * made to it depending on device specific flags, compilation options, and
   * global variable (boot or module load time) settings.
   *
   * A specific LUN is scanned via an INQUIRY command; if the LUN has a
   * device attached, a scsi_device is allocated and setup for it.
   *
   * For every id of every channel on the given host:
   *
   * 	Scan LUN 0; if the target responds to LUN 0 (even if there is no
   * 	device or storage attached to LUN 0):
   *
   * 		If LUN 0 has a device attached, allocate and setup a
   * 		scsi_device for it.
   *
   * 		If target is SCSI-3 or up, issue a REPORT LUN, and scan
   * 		all of the LUNs returned by the REPORT LUN; else,
   * 		sequentially scan LUNs up until some maximum is reached,
   * 		or a LUN is seen that cannot have a device attached to it.
   */
  
  #include <linux/module.h>
  #include <linux/moduleparam.h>
  #include <linux/init.h>
  #include <linux/blkdev.h>
  #include <linux/delay.h>
  #include <linux/kthread.h>
  #include <linux/spinlock.h>
  #include <linux/async.h>
  #include <linux/slab.h>
  
  #include <scsi/scsi.h>
  #include <scsi/scsi_cmnd.h>
  #include <scsi/scsi_device.h>
  #include <scsi/scsi_driver.h>
  #include <scsi/scsi_devinfo.h>
  #include <scsi/scsi_host.h>
  #include <scsi/scsi_transport.h>
  #include <scsi/scsi_eh.h>
  
  #include "scsi_priv.h"
  #include "scsi_logging.h"
  
  #define ALLOC_FAILURE_MSG	KERN_ERR "%s: Allocation failure during" \
  	" SCSI scanning, some SCSI devices might not be configured\n"
  
  /*
   * Default timeout
   */
  #define SCSI_TIMEOUT (2*HZ)
  
  /*
   * Prefix values for the SCSI id's (stored in sysfs name field)
   */
  #define SCSI_UID_SER_NUM 'S'
  #define SCSI_UID_UNKNOWN 'Z'
  
  /*
   * Return values of some of the scanning functions.
   *
   * SCSI_SCAN_NO_RESPONSE: no valid response received from the target, this
   * includes allocation or general failures preventing IO from being sent.
   *
   * SCSI_SCAN_TARGET_PRESENT: target responded, but no device is available
   * on the given LUN.
   *
   * SCSI_SCAN_LUN_PRESENT: target responded, and a device is available on a
   * given LUN.
   */
  #define SCSI_SCAN_NO_RESPONSE		0
  #define SCSI_SCAN_TARGET_PRESENT	1
  #define SCSI_SCAN_LUN_PRESENT		2
  
  static const char *scsi_null_device_strs = "nullnullnullnull";
  
  #define MAX_SCSI_LUNS	512
  
  #ifdef CONFIG_SCSI_MULTI_LUN
  static unsigned int max_scsi_luns = MAX_SCSI_LUNS;
  #else
  static unsigned int max_scsi_luns = 1;
  #endif
  
  module_param_named(max_luns, max_scsi_luns, uint, S_IRUGO|S_IWUSR);
  MODULE_PARM_DESC(max_luns,
  		 "last scsi LUN (should be between 1 and 2^32-1)");
  
  #ifdef CONFIG_SCSI_SCAN_ASYNC
  #define SCSI_SCAN_TYPE_DEFAULT "async"
  #else
  #define SCSI_SCAN_TYPE_DEFAULT "sync"
  #endif
  
  static char scsi_scan_type[6] = SCSI_SCAN_TYPE_DEFAULT;
  
  module_param_string(scan, scsi_scan_type, sizeof(scsi_scan_type), S_IRUGO);
  MODULE_PARM_DESC(scan, "sync, async or none");
  
  /*
   * max_scsi_report_luns: the maximum number of LUNS that will be
   * returned from the REPORT LUNS command. 8 times this value must
   * be allocated. In theory this could be up to an 8 byte value, but
   * in practice, the maximum number of LUNs suppored by any device
   * is about 16k.
   */
  static unsigned int max_scsi_report_luns = 511;
  
  module_param_named(max_report_luns, max_scsi_report_luns, uint, S_IRUGO|S_IWUSR);
  MODULE_PARM_DESC(max_report_luns,
  		 "REPORT LUNS maximum number of LUNS received (should be"
  		 " between 1 and 16384)");
  
  static unsigned int scsi_inq_timeout = SCSI_TIMEOUT/HZ + 18;
  
  module_param_named(inq_timeout, scsi_inq_timeout, uint, S_IRUGO|S_IWUSR);
  MODULE_PARM_DESC(inq_timeout, 
  		 "Timeout (in seconds) waiting for devices to answer INQUIRY."
  		 " Default is 20. Some devices may need more; most need less.");
  
  /* This lock protects only this list */
  static DEFINE_SPINLOCK(async_scan_lock);
  static LIST_HEAD(scanning_hosts);
  
  struct async_scan_data {
  	struct list_head list;
  	struct Scsi_Host *shost;
  	struct completion prev_finished;
  };
  
  /**
   * scsi_complete_async_scans - Wait for asynchronous scans to complete
   *
   * When this function returns, any host which started scanning before
   * this function was called will have finished its scan.  Hosts which
   * started scanning after this function was called may or may not have
   * finished.
   */
  int scsi_complete_async_scans(void)
  {
  	struct async_scan_data *data;
  
  	do {
  		if (list_empty(&scanning_hosts))
  			return 0;
  		/* If we can't get memory immediately, that's OK.  Just
  		 * sleep a little.  Even if we never get memory, the async
  		 * scans will finish eventually.
  		 */
  		data = kmalloc(sizeof(*data), GFP_KERNEL);
  		if (!data)
  			msleep(1);
  	} while (!data);
  
  	data->shost = NULL;
  	init_completion(&data->prev_finished);
  
  	spin_lock(&async_scan_lock);
  	/* Check that there's still somebody else on the list */
  	if (list_empty(&scanning_hosts))
  		goto done;
  	list_add_tail(&data->list, &scanning_hosts);
  	spin_unlock(&async_scan_lock);
  
  	printk(KERN_INFO "scsi: waiting for bus probes to complete ...\n");
  	wait_for_completion(&data->prev_finished);
  
  	spin_lock(&async_scan_lock);
  	list_del(&data->list);
  	if (!list_empty(&scanning_hosts)) {
  		struct async_scan_data *next = list_entry(scanning_hosts.next,
  				struct async_scan_data, list);
  		complete(&next->prev_finished);
  	}
   done:
  	spin_unlock(&async_scan_lock);
  
  	kfree(data);
  	return 0;
  }
  
  /* Only exported for the benefit of scsi_wait_scan */
  EXPORT_SYMBOL_GPL(scsi_complete_async_scans);
  
  #ifndef MODULE
  /*
   * For async scanning we need to wait for all the scans to complete before
   * trying to mount the root fs.  Otherwise non-modular drivers may not be ready
   * yet.
   */
  late_initcall(scsi_complete_async_scans);
  #endif
  
  /**
   * scsi_unlock_floptical - unlock device via a special MODE SENSE command
   * @sdev:	scsi device to send command to
   * @result:	area to store the result of the MODE SENSE
   *
   * Description:
   *     Send a vendor specific MODE SENSE (not a MODE SELECT) command.
   *     Called for BLIST_KEY devices.
   **/
  static void scsi_unlock_floptical(struct scsi_device *sdev,
  				  unsigned char *result)
  {
  	unsigned char scsi_cmd[MAX_COMMAND_SIZE];
  
  	printk(KERN_NOTICE "scsi: unlocking floptical drive\n");
  	scsi_cmd[0] = MODE_SENSE;
  	scsi_cmd[1] = 0;
  	scsi_cmd[2] = 0x2e;
  	scsi_cmd[3] = 0;
  	scsi_cmd[4] = 0x2a;     /* size */
  	scsi_cmd[5] = 0;
  	scsi_execute_req(sdev, scsi_cmd, DMA_FROM_DEVICE, result, 0x2a, NULL,
  			 SCSI_TIMEOUT, 3, NULL);
  }
  
  /**
   * scsi_alloc_sdev - allocate and setup a scsi_Device
   * @starget: which target to allocate a &scsi_device for
   * @lun: which lun
   * @hostdata: usually NULL and set by ->slave_alloc instead
   *
   * Description:
   *     Allocate, initialize for io, and return a pointer to a scsi_Device.
   *     Stores the @shost, @channel, @id, and @lun in the scsi_Device, and
   *     adds scsi_Device to the appropriate list.
   *
   * Return value:
   *     scsi_Device pointer, or NULL on failure.
   **/
  static struct scsi_device *scsi_alloc_sdev(struct scsi_target *starget,
  					   unsigned int lun, void *hostdata)
  {
  	struct scsi_device *sdev;
  	int display_failure_msg = 1, ret;
  	struct Scsi_Host *shost = dev_to_shost(starget->dev.parent);
  	extern void scsi_evt_thread(struct work_struct *work);
  	extern void scsi_requeue_run_queue(struct work_struct *work);
  
  	sdev = kzalloc(sizeof(*sdev) + shost->transportt->device_size,
  		       GFP_ATOMIC);
  	if (!sdev)
  		goto out;
  
  	sdev->vendor = scsi_null_device_strs;
  	sdev->model = scsi_null_device_strs;
  	sdev->rev = scsi_null_device_strs;
  	sdev->host = shost;
  	sdev->queue_ramp_up_period = SCSI_DEFAULT_RAMP_UP_PERIOD;
  	sdev->id = starget->id;
  	sdev->lun = lun;
  	sdev->channel = starget->channel;
  	sdev->sdev_state = SDEV_CREATED;
  	INIT_LIST_HEAD(&sdev->siblings);
  	INIT_LIST_HEAD(&sdev->same_target_siblings);
  	INIT_LIST_HEAD(&sdev->cmd_list);
  	INIT_LIST_HEAD(&sdev->starved_entry);
  	INIT_LIST_HEAD(&sdev->event_list);
  	spin_lock_init(&sdev->list_lock);
  	INIT_WORK(&sdev->event_work, scsi_evt_thread);
  	INIT_WORK(&sdev->requeue_work, scsi_requeue_run_queue);
  
  	sdev->sdev_gendev.parent = get_device(&starget->dev);
  	sdev->sdev_target = starget;
  
  	/* usually NULL and set by ->slave_alloc instead */
  	sdev->hostdata = hostdata;
  
  	/* if the device needs this changing, it may do so in the
  	 * slave_configure function */
  	sdev->max_device_blocked = SCSI_DEFAULT_DEVICE_BLOCKED;
  
  	/*
  	 * Some low level driver could use device->type
  	 */
  	sdev->type = -1;
  
  	/*
  	 * Assume that the device will have handshaking problems,
  	 * and then fix this field later if it turns out it
  	 * doesn't
  	 */
  	sdev->borken = 1;
  
  	sdev->request_queue = scsi_alloc_queue(sdev);
  	if (!sdev->request_queue) {
  		/* release fn is set up in scsi_sysfs_device_initialise, so
  		 * have to free and put manually here */
  		put_device(&starget->dev);
  		kfree(sdev);
  		goto out;
  	}
  	blk_get_queue(sdev->request_queue);
  	sdev->request_queue->queuedata = sdev;
  	scsi_adjust_queue_depth(sdev, 0, sdev->host->cmd_per_lun);
  
  	scsi_sysfs_device_initialize(sdev);
  
  	if (shost->hostt->slave_alloc) {
  		ret = shost->hostt->slave_alloc(sdev);
  		if (ret) {
  			/*
  			 * if LLDD reports slave not present, don't clutter
  			 * console with alloc failure messages
  			 */
  			if (ret == -ENXIO)
  				display_failure_msg = 0;
  			goto out_device_destroy;
  		}
  	}
  
  	return sdev;
  
  out_device_destroy:
  	scsi_device_set_state(sdev, SDEV_DEL);
  	transport_destroy_device(&sdev->sdev_gendev);
  	put_device(&sdev->sdev_dev);
  	put_device(&sdev->sdev_gendev);
  out:
  	if (display_failure_msg)
  		printk(ALLOC_FAILURE_MSG, __func__);
  	return NULL;
  }
  
  static void scsi_target_destroy(struct scsi_target *starget)
  {
  	struct device *dev = &starget->dev;
  	struct Scsi_Host *shost = dev_to_shost(dev->parent);
  	unsigned long flags;
  
  	transport_destroy_device(dev);
  	spin_lock_irqsave(shost->host_lock, flags);
  	if (shost->hostt->target_destroy)
  		shost->hostt->target_destroy(starget);
  	list_del_init(&starget->siblings);
  	spin_unlock_irqrestore(shost->host_lock, flags);
  	put_device(dev);
  }
  
  static void scsi_target_dev_release(struct device *dev)
  {
  	struct device *parent = dev->parent;
  	struct scsi_target *starget = to_scsi_target(dev);
  
  	kfree(starget);
  	put_device(parent);
  }
  
  static struct device_type scsi_target_type = {
  	.name =		"scsi_target",
  	.release =	scsi_target_dev_release,
  };
  
  int scsi_is_target_device(const struct device *dev)
  {
  	return dev->type == &scsi_target_type;
  }
  EXPORT_SYMBOL(scsi_is_target_device);
  
  static struct scsi_target *__scsi_find_target(struct device *parent,
  					      int channel, uint id)
  {
  	struct scsi_target *starget, *found_starget = NULL;
  	struct Scsi_Host *shost = dev_to_shost(parent);
  	/*
  	 * Search for an existing target for this sdev.
  	 */
  	list_for_each_entry(starget, &shost->__targets, siblings) {
  		if (starget->id == id &&
  		    starget->channel == channel) {
  			found_starget = starget;
  			break;
  		}
  	}
  	if (found_starget)
  		get_device(&found_starget->dev);
  
  	return found_starget;
  }
  
  /**
   * scsi_alloc_target - allocate a new or find an existing target
   * @parent:	parent of the target (need not be a scsi host)
   * @channel:	target channel number (zero if no channels)
   * @id:		target id number
   *
   * Return an existing target if one exists, provided it hasn't already
   * gone into STARGET_DEL state, otherwise allocate a new target.
   *
   * The target is returned with an incremented reference, so the caller
   * is responsible for both reaping and doing a last put
   */
  static struct scsi_target *scsi_alloc_target(struct device *parent,
  					     int channel, uint id)
  {
  	struct Scsi_Host *shost = dev_to_shost(parent);
  	struct device *dev = NULL;
  	unsigned long flags;
  	const int size = sizeof(struct scsi_target)
  		+ shost->transportt->target_size;
  	struct scsi_target *starget;
  	struct scsi_target *found_target;
  	int error;
  
  	starget = kzalloc(size, GFP_KERNEL);
  	if (!starget) {
  		printk(KERN_ERR "%s: allocation failure\n", __func__);
  		return NULL;
  	}
  	dev = &starget->dev;
  	device_initialize(dev);
  	starget->reap_ref = 1;
  	dev->parent = get_device(parent);
  	dev_set_name(dev, "target%d:%d:%d", shost->host_no, channel, id);
  	dev->bus = &scsi_bus_type;
  	dev->type = &scsi_target_type;
  	starget->id = id;
  	starget->channel = channel;
  	starget->can_queue = 0;
  	INIT_LIST_HEAD(&starget->siblings);
  	INIT_LIST_HEAD(&starget->devices);
  	starget->state = STARGET_CREATED;
  	starget->scsi_level = SCSI_2;
  	starget->max_target_blocked = SCSI_DEFAULT_TARGET_BLOCKED;
   retry:
  	spin_lock_irqsave(shost->host_lock, flags);
  
  	found_target = __scsi_find_target(parent, channel, id);
  	if (found_target)
  		goto found;
  
  	list_add_tail(&starget->siblings, &shost->__targets);
  	spin_unlock_irqrestore(shost->host_lock, flags);
  	/* allocate and add */
  	transport_setup_device(dev);
  	if (shost->hostt->target_alloc) {
  		error = shost->hostt->target_alloc(starget);
  
  		if(error) {
  			dev_printk(KERN_ERR, dev, "target allocation failed, error %d\n", error);
  			/* don't want scsi_target_reap to do the final
  			 * put because it will be under the host lock */
  			scsi_target_destroy(starget);
  			return NULL;
  		}
  	}
  	get_device(dev);
  
  	return starget;
  
   found:
  	found_target->reap_ref++;
  	spin_unlock_irqrestore(shost->host_lock, flags);
  	if (found_target->state != STARGET_DEL) {
  		put_device(dev);
  		return found_target;
  	}
  	/* Unfortunately, we found a dying target; need to
  	 * wait until it's dead before we can get a new one */
  	put_device(&found_target->dev);
  	flush_scheduled_work();
  	goto retry;
  }
  
  static void scsi_target_reap_usercontext(struct work_struct *work)
  {
  	struct scsi_target *starget =
  		container_of(work, struct scsi_target, ew.work);
  
  	transport_remove_device(&starget->dev);
  	device_del(&starget->dev);
  	scsi_target_destroy(starget);
  }
  
  /**
   * scsi_target_reap - check to see if target is in use and destroy if not
   * @starget: target to be checked
   *
   * This is used after removing a LUN or doing a last put of the target
   * it checks atomically that nothing is using the target and removes
   * it if so.
   */
  void scsi_target_reap(struct scsi_target *starget)
  {
  	struct Scsi_Host *shost = dev_to_shost(starget->dev.parent);
  	unsigned long flags;
  	enum scsi_target_state state;
  	int empty = 0;
  
  	spin_lock_irqsave(shost->host_lock, flags);
  	state = starget->state;
  	if (--starget->reap_ref == 0 && list_empty(&starget->devices)) {
  		empty = 1;
  		starget->state = STARGET_DEL;
  	}
  	spin_unlock_irqrestore(shost->host_lock, flags);
  
  	if (!empty)
  		return;
  
  	BUG_ON(state == STARGET_DEL);
  	if (state == STARGET_CREATED)
  		scsi_target_destroy(starget);
  	else
  		execute_in_process_context(scsi_target_reap_usercontext,
  					   &starget->ew);
  }
  
  /**
   * sanitize_inquiry_string - remove non-graphical chars from an INQUIRY result string
   * @s: INQUIRY result string to sanitize
   * @len: length of the string
   *
   * Description:
   *	The SCSI spec says that INQUIRY vendor, product, and revision
   *	strings must consist entirely of graphic ASCII characters,
   *	padded on the right with spaces.  Since not all devices obey
   *	this rule, we will replace non-graphic or non-ASCII characters
   *	with spaces.  Exception: a NUL character is interpreted as a
   *	string terminator, so all the following characters are set to
   *	spaces.
   **/
  static void sanitize_inquiry_string(unsigned char *s, int len)
  {
  	int terminated = 0;
  
  	for (; len > 0; (--len, ++s)) {
  		if (*s == 0)
  			terminated = 1;
  		if (terminated || *s < 0x20 || *s > 0x7e)
  			*s = ' ';
  	}
  }
  
  /**
   * scsi_probe_lun - probe a single LUN using a SCSI INQUIRY
   * @sdev:	scsi_device to probe
   * @inq_result:	area to store the INQUIRY result
   * @result_len: len of inq_result
   * @bflags:	store any bflags found here
   *
   * Description:
   *     Probe the lun associated with @req using a standard SCSI INQUIRY;
   *
   *     If the INQUIRY is successful, zero is returned and the
   *     INQUIRY data is in @inq_result; the scsi_level and INQUIRY length
   *     are copied to the scsi_device any flags value is stored in *@bflags.
   **/
  static int scsi_probe_lun(struct scsi_device *sdev, unsigned char *inq_result,
  			  int result_len, int *bflags)
  {
  	unsigned char scsi_cmd[MAX_COMMAND_SIZE];
  	int first_inquiry_len, try_inquiry_len, next_inquiry_len;
  	int response_len = 0;
  	int pass, count, result;
  	struct scsi_sense_hdr sshdr;
  
  	*bflags = 0;
  
  	/* Perform up to 3 passes.  The first pass uses a conservative
  	 * transfer length of 36 unless sdev->inquiry_len specifies a
  	 * different value. */
  	first_inquiry_len = sdev->inquiry_len ? sdev->inquiry_len : 36;
  	try_inquiry_len = first_inquiry_len;
  	pass = 1;
  
   next_pass:
  	SCSI_LOG_SCAN_BUS(3, sdev_printk(KERN_INFO, sdev,
  				"scsi scan: INQUIRY pass %d length %d\n",
  				pass, try_inquiry_len));
  
  	/* Each pass gets up to three chances to ignore Unit Attention */
  	for (count = 0; count < 3; ++count) {
  		int resid;
  
  		memset(scsi_cmd, 0, 6);
  		scsi_cmd[0] = INQUIRY;
  		scsi_cmd[4] = (unsigned char) try_inquiry_len;
  
  		memset(inq_result, 0, try_inquiry_len);
  
  		result = scsi_execute_req(sdev,  scsi_cmd, DMA_FROM_DEVICE,
  					  inq_result, try_inquiry_len, &sshdr,
  					  HZ / 2 + HZ * scsi_inq_timeout, 3,
  					  &resid);
  
  		SCSI_LOG_SCAN_BUS(3, printk(KERN_INFO "scsi scan: INQUIRY %s "
  				"with code 0x%x\n",
  				result ? "failed" : "successful", result));
  
  		if (result) {
  			/*
  			 * not-ready to ready transition [asc/ascq=0x28/0x0]
  			 * or power-on, reset [asc/ascq=0x29/0x0], continue.
  			 * INQUIRY should not yield UNIT_ATTENTION
  			 * but many buggy devices do so anyway. 
  			 */
  			if ((driver_byte(result) & DRIVER_SENSE) &&
  			    scsi_sense_valid(&sshdr)) {
  				if ((sshdr.sense_key == UNIT_ATTENTION) &&
  				    ((sshdr.asc == 0x28) ||
  				     (sshdr.asc == 0x29)) &&
  				    (sshdr.ascq == 0))
  					continue;
  			}
  		} else {
  			/*
  			 * if nothing was transferred, we try
  			 * again. It's a workaround for some USB
  			 * devices.
  			 */
  			if (resid == try_inquiry_len)
  				continue;
  		}
  		break;
  	}
  
  	if (result == 0) {
  		sanitize_inquiry_string(&inq_result[8], 8);
  		sanitize_inquiry_string(&inq_result[16], 16);
  		sanitize_inquiry_string(&inq_result[32], 4);
  
  		response_len = inq_result[4] + 5;
  		if (response_len > 255)
  			response_len = first_inquiry_len;	/* sanity */
  
  		/*
  		 * Get any flags for this device.
  		 *
  		 * XXX add a bflags to scsi_device, and replace the
  		 * corresponding bit fields in scsi_device, so bflags
  		 * need not be passed as an argument.
  		 */
  		*bflags = scsi_get_device_flags(sdev, &inq_result[8],
  				&inq_result[16]);
  
  		/* When the first pass succeeds we gain information about
  		 * what larger transfer lengths might work. */
  		if (pass == 1) {
  			if (BLIST_INQUIRY_36 & *bflags)
  				next_inquiry_len = 36;
  			else if (BLIST_INQUIRY_58 & *bflags)
  				next_inquiry_len = 58;
  			else if (sdev->inquiry_len)
  				next_inquiry_len = sdev->inquiry_len;
  			else
  				next_inquiry_len = response_len;
  
  			/* If more data is available perform the second pass */
  			if (next_inquiry_len > try_inquiry_len) {
  				try_inquiry_len = next_inquiry_len;
  				pass = 2;
  				goto next_pass;
  			}
  		}
  
  	} else if (pass == 2) {
  		printk(KERN_INFO "scsi scan: %d byte inquiry failed.  "
  				"Consider BLIST_INQUIRY_36 for this device\n",
  				try_inquiry_len);
  
  		/* If this pass failed, the third pass goes back and transfers
  		 * the same amount as we successfully got in the first pass. */
  		try_inquiry_len = first_inquiry_len;
  		pass = 3;
  		goto next_pass;
  	}
  
  	/* If the last transfer attempt got an error, assume the
  	 * peripheral doesn't exist or is dead. */
  	if (result)
  		return -EIO;
  
  	/* Don't report any more data than the device says is valid */
  	sdev->inquiry_len = min(try_inquiry_len, response_len);
  
  	/*
  	 * XXX Abort if the response length is less than 36? If less than
  	 * 32, the lookup of the device flags (above) could be invalid,
  	 * and it would be possible to take an incorrect action - we do
  	 * not want to hang because of a short INQUIRY. On the flip side,
  	 * if the device is spun down or becoming ready (and so it gives a
  	 * short INQUIRY), an abort here prevents any further use of the
  	 * device, including spin up.
  	 *
  	 * On the whole, the best approach seems to be to assume the first
  	 * 36 bytes are valid no matter what the device says.  That's
  	 * better than copying < 36 bytes to the inquiry-result buffer
  	 * and displaying garbage for the Vendor, Product, or Revision
  	 * strings.
  	 */
  	if (sdev->inquiry_len < 36) {
  		printk(KERN_INFO "scsi scan: INQUIRY result too short (%d),"
  				" using 36\n", sdev->inquiry_len);
  		sdev->inquiry_len = 36;
  	}
  
  	/*
  	 * Related to the above issue:
  	 *
  	 * XXX Devices (disk or all?) should be sent a TEST UNIT READY,
  	 * and if not ready, sent a START_STOP to start (maybe spin up) and
  	 * then send the INQUIRY again, since the INQUIRY can change after
  	 * a device is initialized.
  	 *
  	 * Ideally, start a device if explicitly asked to do so.  This
  	 * assumes that a device is spun up on power on, spun down on
  	 * request, and then spun up on request.
  	 */
  
  	/*
  	 * The scanning code needs to know the scsi_level, even if no
  	 * device is attached at LUN 0 (SCSI_SCAN_TARGET_PRESENT) so
  	 * non-zero LUNs can be scanned.
  	 */
  	sdev->scsi_level = inq_result[2] & 0x07;
  	if (sdev->scsi_level >= 2 ||
  	    (sdev->scsi_level == 1 && (inq_result[3] & 0x0f) == 1))
  		sdev->scsi_level++;
  	sdev->sdev_target->scsi_level = sdev->scsi_level;
  
  	return 0;
  }
  
  /**
   * scsi_add_lun - allocate and fully initialze a scsi_device
   * @sdev:	holds information to be stored in the new scsi_device
   * @inq_result:	holds the result of a previous INQUIRY to the LUN
   * @bflags:	black/white list flag
   * @async:	1 if this device is being scanned asynchronously
   *
   * Description:
   *     Initialize the scsi_device @sdev.  Optionally set fields based
   *     on values in *@bflags.
   *
   * Return:
   *     SCSI_SCAN_NO_RESPONSE: could not allocate or setup a scsi_device
   *     SCSI_SCAN_LUN_PRESENT: a new scsi_device was allocated and initialized
   **/
  static int scsi_add_lun(struct scsi_device *sdev, unsigned char *inq_result,
  		int *bflags, int async)
  {
  	int ret;
  
  	/*
  	 * XXX do not save the inquiry, since it can change underneath us,
  	 * save just vendor/model/rev.
  	 *
  	 * Rather than save it and have an ioctl that retrieves the saved
  	 * value, have an ioctl that executes the same INQUIRY code used
  	 * in scsi_probe_lun, let user level programs doing INQUIRY
  	 * scanning run at their own risk, or supply a user level program
  	 * that can correctly scan.
  	 */
  
  	/*
  	 * Copy at least 36 bytes of INQUIRY data, so that we don't
  	 * dereference unallocated memory when accessing the Vendor,
  	 * Product, and Revision strings.  Badly behaved devices may set
  	 * the INQUIRY Additional Length byte to a small value, indicating
  	 * these strings are invalid, but often they contain plausible data
  	 * nonetheless.  It doesn't matter if the device sent < 36 bytes
  	 * total, since scsi_probe_lun() initializes inq_result with 0s.
  	 */
  	sdev->inquiry = kmemdup(inq_result,
  				max_t(size_t, sdev->inquiry_len, 36),
  				GFP_ATOMIC);
  	if (sdev->inquiry == NULL)
  		return SCSI_SCAN_NO_RESPONSE;
  
  	sdev->vendor = (char *) (sdev->inquiry + 8);
  	sdev->model = (char *) (sdev->inquiry + 16);
  	sdev->rev = (char *) (sdev->inquiry + 32);
  
  	if (*bflags & BLIST_ISROM) {
  		sdev->type = TYPE_ROM;
  		sdev->removable = 1;
  	} else {
  		sdev->type = (inq_result[0] & 0x1f);
  		sdev->removable = (inq_result[1] & 0x80) >> 7;
  	}
  
  	switch (sdev->type) {
  	case TYPE_RBC:
  	case TYPE_TAPE:
  	case TYPE_DISK:
  	case TYPE_PRINTER:
  	case TYPE_MOD:
  	case TYPE_PROCESSOR:
  	case TYPE_SCANNER:
  	case TYPE_MEDIUM_CHANGER:
  	case TYPE_ENCLOSURE:
  	case TYPE_COMM:
  	case TYPE_RAID:
  	case TYPE_OSD:
  		sdev->writeable = 1;
  		break;
  	case TYPE_ROM:
  	case TYPE_WORM:
  		sdev->writeable = 0;
  		break;
  	default:
  		printk(KERN_INFO "scsi: unknown device type %d\n", sdev->type);
  	}
  
  	if (sdev->type == TYPE_RBC || sdev->type == TYPE_ROM) {
  		/* RBC and MMC devices can return SCSI-3 compliance and yet
  		 * still not support REPORT LUNS, so make them act as
  		 * BLIST_NOREPORTLUN unless BLIST_REPORTLUN2 is
  		 * specifically set */
  		if ((*bflags & BLIST_REPORTLUN2) == 0)
  			*bflags |= BLIST_NOREPORTLUN;
  	}
  
  	/*
  	 * For a peripheral qualifier (PQ) value of 1 (001b), the SCSI
  	 * spec says: The device server is capable of supporting the
  	 * specified peripheral device type on this logical unit. However,
  	 * the physical device is not currently connected to this logical
  	 * unit.
  	 *
  	 * The above is vague, as it implies that we could treat 001 and
  	 * 011 the same. Stay compatible with previous code, and create a
  	 * scsi_device for a PQ of 1
  	 *
  	 * Don't set the device offline here; rather let the upper
  	 * level drivers eval the PQ to decide whether they should
  	 * attach. So remove ((inq_result[0] >> 5) & 7) == 1 check.
  	 */ 
  
  	sdev->inq_periph_qual = (inq_result[0] >> 5) & 7;
  	sdev->lockable = sdev->removable;
  	sdev->soft_reset = (inq_result[7] & 1) && ((inq_result[3] & 7) == 2);
  
  	if (sdev->scsi_level >= SCSI_3 ||
  			(sdev->inquiry_len > 56 && inq_result[56] & 0x04))
  		sdev->ppr = 1;
  	if (inq_result[7] & 0x60)
  		sdev->wdtr = 1;
  	if (inq_result[7] & 0x10)
  		sdev->sdtr = 1;
  
  	sdev_printk(KERN_NOTICE, sdev, "%s %.8s %.16s %.4s PQ: %d "
  			"ANSI: %d%s\n", scsi_device_type(sdev->type),
  			sdev->vendor, sdev->model, sdev->rev,
  			sdev->inq_periph_qual, inq_result[2] & 0x07,
  			(inq_result[3] & 0x0f) == 1 ? " CCS" : "");
  
  	if ((sdev->scsi_level >= SCSI_2) && (inq_result[7] & 2) &&
  	    !(*bflags & BLIST_NOTQ))
  		sdev->tagged_supported = 1;
  
  	/*
  	 * Some devices (Texel CD ROM drives) have handshaking problems
  	 * when used with the Seagate controllers. borken is initialized
  	 * to 1, and then set it to 0 here.
  	 */
  	if ((*bflags & BLIST_BORKEN) == 0)
  		sdev->borken = 0;
  
  	if (*bflags & BLIST_NO_ULD_ATTACH)
  		sdev->no_uld_attach = 1;
  
  	/*
  	 * Apparently some really broken devices (contrary to the SCSI
  	 * standards) need to be selected without asserting ATN
  	 */
  	if (*bflags & BLIST_SELECT_NO_ATN)
  		sdev->select_no_atn = 1;
  
  	/*
  	 * Maximum 512 sector transfer length
  	 * broken RA4x00 Compaq Disk Array
  	 */
  	if (*bflags & BLIST_MAX_512)
  		blk_queue_max_hw_sectors(sdev->request_queue, 512);
  
  	/*
  	 * Some devices may not want to have a start command automatically
  	 * issued when a device is added.
  	 */
  	if (*bflags & BLIST_NOSTARTONADD)
  		sdev->no_start_on_add = 1;
  
  	if (*bflags & BLIST_SINGLELUN)
  		scsi_target(sdev)->single_lun = 1;
  
  	sdev->use_10_for_rw = 1;
  
  	if (*bflags & BLIST_MS_SKIP_PAGE_08)
  		sdev->skip_ms_page_8 = 1;
  
  	if (*bflags & BLIST_MS_SKIP_PAGE_3F)
  		sdev->skip_ms_page_3f = 1;
  
  	if (*bflags & BLIST_USE_10_BYTE_MS)
  		sdev->use_10_for_ms = 1;
  
  	/* set the device running here so that slave configure
  	 * may do I/O */
  	ret = scsi_device_set_state(sdev, SDEV_RUNNING);
  	if (ret) {
  		ret = scsi_device_set_state(sdev, SDEV_BLOCK);
  
  		if (ret) {
  			sdev_printk(KERN_ERR, sdev,
  				    "in wrong state %s to complete scan\n",
  				    scsi_device_state_name(sdev->sdev_state));
  			return SCSI_SCAN_NO_RESPONSE;
  		}
  	}
  
  	if (*bflags & BLIST_MS_192_BYTES_FOR_3F)
  		sdev->use_192_bytes_for_3f = 1;
  
  	if (*bflags & BLIST_NOT_LOCKABLE)
  		sdev->lockable = 0;
  
  	if (*bflags & BLIST_RETRY_HWERROR)
  		sdev->retry_hwerror = 1;
  
  	transport_configure_device(&sdev->sdev_gendev);
  
  	if (sdev->host->hostt->slave_configure) {
  		ret = sdev->host->hostt->slave_configure(sdev);
  		if (ret) {
  			/*
  			 * if LLDD reports slave not present, don't clutter
  			 * console with alloc failure messages
  			 */
  			if (ret != -ENXIO) {
  				sdev_printk(KERN_ERR, sdev,
  					"failed to configure device\n");
  			}
  			return SCSI_SCAN_NO_RESPONSE;
  		}
  	}
  
  	sdev->max_queue_depth = sdev->queue_depth;
  
  	/*
  	 * Ok, the device is now all set up, we can
  	 * register it and tell the rest of the kernel
  	 * about it.
  	 */
  	if (!async && scsi_sysfs_add_sdev(sdev) != 0)
  		return SCSI_SCAN_NO_RESPONSE;
  
  	return SCSI_SCAN_LUN_PRESENT;
  }
  
  #ifdef CONFIG_SCSI_LOGGING
  /** 
   * scsi_inq_str - print INQUIRY data from min to max index, strip trailing whitespace
   * @buf:   Output buffer with at least end-first+1 bytes of space
   * @inq:   Inquiry buffer (input)
   * @first: Offset of string into inq
   * @end:   Index after last character in inq
   */
  static unsigned char *scsi_inq_str(unsigned char *buf, unsigned char *inq,
  				   unsigned first, unsigned end)
  {
  	unsigned term = 0, idx;
  
  	for (idx = 0; idx + first < end && idx + first < inq[4] + 5; idx++) {
  		if (inq[idx+first] > ' ') {
  			buf[idx] = inq[idx+first];
  			term = idx+1;
  		} else {
  			buf[idx] = ' ';
  		}
  	}
  	buf[term] = 0;
  	return buf;
  }
  #endif
  
  /**
   * scsi_probe_and_add_lun - probe a LUN, if a LUN is found add it
   * @starget:	pointer to target device structure
   * @lun:	LUN of target device
   * @bflagsp:	store bflags here if not NULL
   * @sdevp:	probe the LUN corresponding to this scsi_device
   * @rescan:     if nonzero skip some code only needed on first scan
   * @hostdata:	passed to scsi_alloc_sdev()
   *
   * Description:
   *     Call scsi_probe_lun, if a LUN with an attached device is found,
   *     allocate and set it up by calling scsi_add_lun.
   *
   * Return:
   *     SCSI_SCAN_NO_RESPONSE: could not allocate or setup a scsi_device
   *     SCSI_SCAN_TARGET_PRESENT: target responded, but no device is
   *         attached at the LUN
   *     SCSI_SCAN_LUN_PRESENT: a new scsi_device was allocated and initialized
   **/
  static int scsi_probe_and_add_lun(struct scsi_target *starget,
  				  uint lun, int *bflagsp,
  				  struct scsi_device **sdevp, int rescan,
  				  void *hostdata)
  {
  	struct scsi_device *sdev;
  	unsigned char *result;
  	int bflags, res = SCSI_SCAN_NO_RESPONSE, result_len = 256;
  	struct Scsi_Host *shost = dev_to_shost(starget->dev.parent);
  
  	/*
  	 * The rescan flag is used as an optimization, the first scan of a
  	 * host adapter calls into here with rescan == 0.
  	 */
  	sdev = scsi_device_lookup_by_target(starget, lun);
  	if (sdev) {
  		if (rescan || !scsi_device_created(sdev)) {
  			SCSI_LOG_SCAN_BUS(3, printk(KERN_INFO
  				"scsi scan: device exists on %s\n",
  				dev_name(&sdev->sdev_gendev)));
  			if (sdevp)
  				*sdevp = sdev;
  			else
  				scsi_device_put(sdev);
  
  			if (bflagsp)
  				*bflagsp = scsi_get_device_flags(sdev,
  								 sdev->vendor,
  								 sdev->model);
  			return SCSI_SCAN_LUN_PRESENT;
  		}
  		scsi_device_put(sdev);
  	} else
  		sdev = scsi_alloc_sdev(starget, lun, hostdata);
  	if (!sdev)
  		goto out;
  
  	result = kmalloc(result_len, GFP_ATOMIC |
  			((shost->unchecked_isa_dma) ? __GFP_DMA : 0));
  	if (!result)
  		goto out_free_sdev;
  
  	if (scsi_probe_lun(sdev, result, result_len, &bflags))
  		goto out_free_result;
  
  	if (bflagsp)
  		*bflagsp = bflags;
  	/*
  	 * result contains valid SCSI INQUIRY data.
  	 */
  	if (((result[0] >> 5) == 3) && !(bflags & BLIST_ATTACH_PQ3)) {
  		/*
  		 * For a Peripheral qualifier 3 (011b), the SCSI
  		 * spec says: The device server is not capable of
  		 * supporting a physical device on this logical
  		 * unit.
  		 *
  		 * For disks, this implies that there is no
  		 * logical disk configured at sdev->lun, but there
  		 * is a target id responding.
  		 */
  		SCSI_LOG_SCAN_BUS(2, sdev_printk(KERN_INFO, sdev, "scsi scan:"
  				   " peripheral qualifier of 3, device not"
  				   " added\n"))
  		if (lun == 0) {
  			SCSI_LOG_SCAN_BUS(1, {
  				unsigned char vend[9];
  				unsigned char mod[17];
  
  				sdev_printk(KERN_INFO, sdev,
  					"scsi scan: consider passing scsi_mod."
  					"dev_flags=%s:%s:0x240 or 0x1000240\n",
  					scsi_inq_str(vend, result, 8, 16),
  					scsi_inq_str(mod, result, 16, 32));
  			});
  
  		}
  
  		res = SCSI_SCAN_TARGET_PRESENT;
  		goto out_free_result;
  	}
  
  	/*
  	 * Some targets may set slight variations of PQ and PDT to signal
  	 * that no LUN is present, so don't add sdev in these cases.
  	 * Two specific examples are:
  	 * 1) NetApp targets: return PQ=1, PDT=0x1f
  	 * 2) USB UFI: returns PDT=0x1f, with the PQ bits being "reserved"
  	 *    in the UFI 1.0 spec (we cannot rely on reserved bits).
  	 *
  	 * References:
  	 * 1) SCSI SPC-3, pp. 145-146
  	 * PQ=1: "A peripheral device having the specified peripheral
  	 * device type is not connected to this logical unit. However, the
  	 * device server is capable of supporting the specified peripheral
  	 * device type on this logical unit."
  	 * PDT=0x1f: "Unknown or no device type"
  	 * 2) USB UFI 1.0, p. 20
  	 * PDT=00h Direct-access device (floppy)
  	 * PDT=1Fh none (no FDD connected to the requested logical unit)
  	 */
  	if (((result[0] >> 5) == 1 || starget->pdt_1f_for_no_lun) &&
  	    (result[0] & 0x1f) == 0x1f &&
  	    !scsi_is_wlun(lun)) {
  		SCSI_LOG_SCAN_BUS(3, printk(KERN_INFO
  					"scsi scan: peripheral device type"
  					" of 31, no device added\n"));
  		res = SCSI_SCAN_TARGET_PRESENT;
  		goto out_free_result;
  	}
  
  	res = scsi_add_lun(sdev, result, &bflags, shost->async_scan);
  	if (res == SCSI_SCAN_LUN_PRESENT) {
  		if (bflags & BLIST_KEY) {
  			sdev->lockable = 0;
  			scsi_unlock_floptical(sdev, result);
  		}
  	}
  
   out_free_result:
  	kfree(result);
   out_free_sdev:
  	if (res == SCSI_SCAN_LUN_PRESENT) {
  		if (sdevp) {
  			if (scsi_device_get(sdev) == 0) {
  				*sdevp = sdev;
  			} else {
  				__scsi_remove_device(sdev);
  				res = SCSI_SCAN_NO_RESPONSE;
  			}
  		}
  	} else
  		__scsi_remove_device(sdev);
   out:
  	return res;
  }
  
  /**
   * scsi_sequential_lun_scan - sequentially scan a SCSI target
   * @starget:	pointer to target structure to scan
   * @bflags:	black/white list flag for LUN 0
   * @scsi_level: Which version of the standard does this device adhere to
   * @rescan:     passed to scsi_probe_add_lun()
   *
   * Description:
   *     Generally, scan from LUN 1 (LUN 0 is assumed to already have been
   *     scanned) to some maximum lun until a LUN is found with no device
   *     attached. Use the bflags to figure out any oddities.
   *
   *     Modifies sdevscan->lun.
   **/
  static void scsi_sequential_lun_scan(struct scsi_target *starget,
  				     int bflags, int scsi_level, int rescan)
  {
  	unsigned int sparse_lun, lun, max_dev_lun;
  	struct Scsi_Host *shost = dev_to_shost(starget->dev.parent);
  
  	SCSI_LOG_SCAN_BUS(3, printk(KERN_INFO "scsi scan: Sequential scan of"
  				    "%s\n", dev_name(&starget->dev)));
  
  	max_dev_lun = min(max_scsi_luns, shost->max_lun);
  	/*
  	 * If this device is known to support sparse multiple units,
  	 * override the other settings, and scan all of them. Normally,
  	 * SCSI-3 devices should be scanned via the REPORT LUNS.
  	 */
  	if (bflags & BLIST_SPARSELUN) {
  		max_dev_lun = shost->max_lun;
  		sparse_lun = 1;
  	} else
  		sparse_lun = 0;
  
  	/*
  	 * If less than SCSI_1_CSS, and no special lun scaning, stop
  	 * scanning; this matches 2.4 behaviour, but could just be a bug
  	 * (to continue scanning a SCSI_1_CSS device).
  	 *
  	 * This test is broken.  We might not have any device on lun0 for
  	 * a sparselun device, and if that's the case then how would we
  	 * know the real scsi_level, eh?  It might make sense to just not
  	 * scan any SCSI_1 device for non-0 luns, but that check would best
  	 * go into scsi_alloc_sdev() and just have it return null when asked
  	 * to alloc an sdev for lun > 0 on an already found SCSI_1 device.
  	 *
  	if ((sdevscan->scsi_level < SCSI_1_CCS) &&
  	    ((bflags & (BLIST_FORCELUN | BLIST_SPARSELUN | BLIST_MAX5LUN))
  	     == 0))
  		return;
  	 */
  	/*
  	 * If this device is known to support multiple units, override
  	 * the other settings, and scan all of them.
  	 */
  	if (bflags & BLIST_FORCELUN)
  		max_dev_lun = shost->max_lun;
  	/*
  	 * REGAL CDC-4X: avoid hang after LUN 4
  	 */
  	if (bflags & BLIST_MAX5LUN)
  		max_dev_lun = min(5U, max_dev_lun);
  	/*
  	 * Do not scan SCSI-2 or lower device past LUN 7, unless
  	 * BLIST_LARGELUN.
  	 */
  	if (scsi_level < SCSI_3 && !(bflags & BLIST_LARGELUN))
  		max_dev_lun = min(8U, max_dev_lun);
  
  	/*
  	 * We have already scanned LUN 0, so start at LUN 1. Keep scanning
  	 * until we reach the max, or no LUN is found and we are not
  	 * sparse_lun.
  	 */
  	for (lun = 1; lun < max_dev_lun; ++lun)
  		if ((scsi_probe_and_add_lun(starget, lun, NULL, NULL, rescan,
  					    NULL) != SCSI_SCAN_LUN_PRESENT) &&
  		    !sparse_lun)
  			return;
  }
  
  /**
   * scsilun_to_int - convert a scsi_lun to an int
   * @scsilun:	struct scsi_lun to be converted.
   *
   * Description:
   *     Convert @scsilun from a struct scsi_lun to a four byte host byte-ordered
   *     integer, and return the result. The caller must check for
   *     truncation before using this function.
   *
   * Notes:
   *     The struct scsi_lun is assumed to be four levels, with each level
   *     effectively containing a SCSI byte-ordered (big endian) short; the
   *     addressing bits of each level are ignored (the highest two bits).
   *     For a description of the LUN format, post SCSI-3 see the SCSI
   *     Architecture Model, for SCSI-3 see the SCSI Controller Commands.
   *
   *     Given a struct scsi_lun of: 0a 04 0b 03 00 00 00 00, this function returns
   *     the integer: 0x0b030a04
   **/
  int scsilun_to_int(struct scsi_lun *scsilun)
  {
  	int i;
  	unsigned int lun;
  
  	lun = 0;
  	for (i = 0; i < sizeof(lun); i += 2)
  		lun = lun | (((scsilun->scsi_lun[i] << 8) |
  			      scsilun->scsi_lun[i + 1]) << (i * 8));
  	return lun;
  }
  EXPORT_SYMBOL(scsilun_to_int);
  
  /**
   * int_to_scsilun - reverts an int into a scsi_lun
   * @lun:        integer to be reverted
   * @scsilun:	struct scsi_lun to be set.
   *
   * Description:
   *     Reverts the functionality of the scsilun_to_int, which packed
   *     an 8-byte lun value into an int. This routine unpacks the int
   *     back into the lun value.
   *     Note: the scsilun_to_int() routine does not truly handle all
   *     8bytes of the lun value. This functions restores only as much
   *     as was set by the routine.
   *
   * Notes:
   *     Given an integer : 0x0b030a04,  this function returns a
   *     scsi_lun of : struct scsi_lun of: 0a 04 0b 03 00 00 00 00
   *
   **/
  void int_to_scsilun(unsigned int lun, struct scsi_lun *scsilun)
  {
  	int i;
  
  	memset(scsilun->scsi_lun, 0, sizeof(scsilun->scsi_lun));
  
  	for (i = 0; i < sizeof(lun); i += 2) {
  		scsilun->scsi_lun[i] = (lun >> 8) & 0xFF;
  		scsilun->scsi_lun[i+1] = lun & 0xFF;
  		lun = lun >> 16;
  	}
  }
  EXPORT_SYMBOL(int_to_scsilun);
  
  /**
   * scsi_report_lun_scan - Scan using SCSI REPORT LUN results
   * @starget: which target
   * @bflags: Zero or a mix of BLIST_NOLUN, BLIST_REPORTLUN2, or BLIST_NOREPORTLUN
   * @rescan: nonzero if we can skip code only needed on first scan
   *
   * Description:
   *   Fast scanning for modern (SCSI-3) devices by sending a REPORT LUN command.
   *   Scan the resulting list of LUNs by calling scsi_probe_and_add_lun.
   *
   *   If BLINK_REPORTLUN2 is set, scan a target that supports more than 8
   *   LUNs even if it's older than SCSI-3.
   *   If BLIST_NOREPORTLUN is set, return 1 always.
   *   If BLIST_NOLUN is set, return 0 always.
   *
   * Return:
   *     0: scan completed (or no memory, so further scanning is futile)
   *     1: could not scan with REPORT LUN
   **/
  static int scsi_report_lun_scan(struct scsi_target *starget, int bflags,
  				int rescan)
  {
  	char devname[64];
  	unsigned char scsi_cmd[MAX_COMMAND_SIZE];
  	unsigned int length;
  	unsigned int lun;
  	unsigned int num_luns;
  	unsigned int retries;
  	int result;
  	struct scsi_lun *lunp, *lun_data;
  	u8 *data;
  	struct scsi_sense_hdr sshdr;
  	struct scsi_device *sdev;
  	struct Scsi_Host *shost = dev_to_shost(&starget->dev);
  	int ret = 0;
  
  	/*
  	 * Only support SCSI-3 and up devices if BLIST_NOREPORTLUN is not set.
  	 * Also allow SCSI-2 if BLIST_REPORTLUN2 is set and host adapter does
  	 * support more than 8 LUNs.
  	 */
  	if (bflags & BLIST_NOREPORTLUN)
  		return 1;
  	if (starget->scsi_level < SCSI_2 &&
  	    starget->scsi_level != SCSI_UNKNOWN)
  		return 1;
  	if (starget->scsi_level < SCSI_3 &&
  	    (!(bflags & BLIST_REPORTLUN2) || shost->max_lun <= 8))
  		return 1;
  	if (bflags & BLIST_NOLUN)
  		return 0;
  
  	if (!(sdev = scsi_device_lookup_by_target(starget, 0))) {
  		sdev = scsi_alloc_sdev(starget, 0, NULL);
  		if (!sdev)
  			return 0;
  		if (scsi_device_get(sdev)) {
  			__scsi_remove_device(sdev);
  			return 0;
  		}
  	}
  
  	sprintf(devname, "host %d channel %d id %d",
  		shost->host_no, sdev->channel, sdev->id);
  
  	/*
  	 * Allocate enough to hold the header (the same size as one scsi_lun)
  	 * plus the max number of luns we are requesting.
  	 *
  	 * Reallocating and trying again (with the exact amount we need)
  	 * would be nice, but then we need to somehow limit the size
  	 * allocated based on the available memory and the limits of
  	 * kmalloc - we don't want a kmalloc() failure of a huge value to
  	 * prevent us from finding any LUNs on this target.
  	 */
  	length = (max_scsi_report_luns + 1) * sizeof(struct scsi_lun);
  	lun_data = kmalloc(length, GFP_ATOMIC |
  			   (sdev->host->unchecked_isa_dma ? __GFP_DMA : 0));
  	if (!lun_data) {
  		printk(ALLOC_FAILURE_MSG, __func__);
  		goto out;
  	}
  
  	scsi_cmd[0] = REPORT_LUNS;
  
  	/*
  	 * bytes 1 - 5: reserved, set to zero.
  	 */
  	memset(&scsi_cmd[1], 0, 5);
  
  	/*
  	 * bytes 6 - 9: length of the command.
  	 */
  	scsi_cmd[6] = (unsigned char) (length >> 24) & 0xff;
  	scsi_cmd[7] = (unsigned char) (length >> 16) & 0xff;
  	scsi_cmd[8] = (unsigned char) (length >> 8) & 0xff;
  	scsi_cmd[9] = (unsigned char) length & 0xff;
  
  	scsi_cmd[10] = 0;	/* reserved */
  	scsi_cmd[11] = 0;	/* control */
  
  	/*
  	 * We can get a UNIT ATTENTION, for example a power on/reset, so
  	 * retry a few times (like sd.c does for TEST UNIT READY).
  	 * Experience shows some combinations of adapter/devices get at
  	 * least two power on/resets.
  	 *
  	 * Illegal requests (for devices that do not support REPORT LUNS)
  	 * should come through as a check condition, and will not generate
  	 * a retry.
  	 */
  	for (retries = 0; retries < 3; retries++) {
  		SCSI_LOG_SCAN_BUS(3, printk (KERN_INFO "scsi scan: Sending"
  				" REPORT LUNS to %s (try %d)\n", devname,
  				retries));
  
  		result = scsi_execute_req(sdev, scsi_cmd, DMA_FROM_DEVICE,
  					  lun_data, length, &sshdr,
  					  SCSI_TIMEOUT + 4 * HZ, 3, NULL);
  
  		SCSI_LOG_SCAN_BUS(3, printk (KERN_INFO "scsi scan: REPORT LUNS"
  				" %s (try %d) result 0x%x\n", result
  				?  "failed" : "successful", retries, result));
  		if (result == 0)
  			break;
  		else if (scsi_sense_valid(&sshdr)) {
  			if (sshdr.sense_key != UNIT_ATTENTION)
  				break;
  		}
  	}
  
  	if (result) {
  		/*
  		 * The device probably does not support a REPORT LUN command
  		 */
  		ret = 1;
  		goto out_err;
  	}
  
  	/*
  	 * Get the length from the first four bytes of lun_data.
  	 */
  	data = (u8 *) lun_data->scsi_lun;
  	length = ((data[0] << 24) | (data[1] << 16) |
  		  (data[2] << 8) | (data[3] << 0));
  
  	num_luns = (length / sizeof(struct scsi_lun));
  	if (num_luns > max_scsi_report_luns) {
  		printk(KERN_WARNING "scsi: On %s only %d (max_scsi_report_luns)"
  		       " of %d luns reported, try increasing"
  		       " max_scsi_report_luns.\n", devname,
  		       max_scsi_report_luns, num_luns);
  		num_luns = max_scsi_report_luns;
  	}
  
  	SCSI_LOG_SCAN_BUS(3, sdev_printk (KERN_INFO, sdev,
  		"scsi scan: REPORT LUN scan\n"));
  
  	/*
  	 * Scan the luns in lun_data. The entry at offset 0 is really
  	 * the header, so start at 1 and go up to and including num_luns.
  	 */
  	for (lunp = &lun_data[1]; lunp <= &lun_data[num_luns]; lunp++) {
  		lun = scsilun_to_int(lunp);
  
  		/*
  		 * Check if the unused part of lunp is non-zero, and so
  		 * does not fit in lun.
  		 */
  		if (memcmp(&lunp->scsi_lun[sizeof(lun)], "\0\0\0\0", 4)) {
  			int i;
  
  			/*
  			 * Output an error displaying the LUN in byte order,
  			 * this differs from what linux would print for the
  			 * integer LUN value.
  			 */
  			printk(KERN_WARNING "scsi: %s lun 0x", devname);
  			data = (char *)lunp->scsi_lun;
  			for (i = 0; i < sizeof(struct scsi_lun); i++)
  				printk("%02x", data[i]);
  			printk(" has a LUN larger than currently supported.\n");
  		} else if (lun > sdev->host->max_lun) {
  			printk(KERN_WARNING "scsi: %s lun%d has a LUN larger"
  			       " than allowed by the host adapter\n",
  			       devname, lun);
  		} else {
  			int res;
  
  			res = scsi_probe_and_add_lun(starget,
  				lun, NULL, NULL, rescan, NULL);
  			if (res == SCSI_SCAN_NO_RESPONSE) {
  				/*
  				 * Got some results, but now none, abort.
  				 */
  				sdev_printk(KERN_ERR, sdev,
  					"Unexpected response"
  				        " from lun %d while scanning, scan"
  				        " aborted\n", lun);
  				break;
  			}
  		}
  	}
  
   out_err:
  	kfree(lun_data);
   out:
  	scsi_device_put(sdev);
  	if (scsi_device_created(sdev))
  		/*
  		 * the sdev we used didn't appear in the report luns scan
  		 */
  		__scsi_remove_device(sdev);
  	return ret;
  }
  
  struct scsi_device *__scsi_add_device(struct Scsi_Host *shost, uint channel,
  				      uint id, uint lun, void *hostdata)
  {
  	struct scsi_device *sdev = ERR_PTR(-ENODEV);
  	struct device *parent = &shost->shost_gendev;
  	struct scsi_target *starget;
  
  	if (strncmp(scsi_scan_type, "none", 4) == 0)
  		return ERR_PTR(-ENODEV);
  
  	starget = scsi_alloc_target(parent, channel, id);
  	if (!starget)
  		return ERR_PTR(-ENOMEM);
  	scsi_autopm_get_target(starget);
  
  	mutex_lock(&shost->scan_mutex);
  	if (!shost->async_scan)
  		scsi_complete_async_scans();
  
  	if (scsi_host_scan_allowed(shost) && scsi_autopm_get_host(shost) == 0) {
  		scsi_probe_and_add_lun(starget, lun, NULL, &sdev, 1, hostdata);
  		scsi_autopm_put_host(shost);
  	}
  	mutex_unlock(&shost->scan_mutex);
  	scsi_autopm_put_target(starget);
  	scsi_target_reap(starget);
  	put_device(&starget->dev);
  
  	return sdev;
  }
  EXPORT_SYMBOL(__scsi_add_device);
  
  int scsi_add_device(struct Scsi_Host *host, uint channel,
  		    uint target, uint lun)
  {
  	struct scsi_device *sdev = 
  		__scsi_add_device(host, channel, target, lun, NULL);
  	if (IS_ERR(sdev))
  		return PTR_ERR(sdev);
  
  	scsi_device_put(sdev);
  	return 0;
  }
  EXPORT_SYMBOL(scsi_add_device);
  
  void scsi_rescan_device(struct device *dev)
  {
  	struct scsi_driver *drv;
  	
  	if (!dev->driver)
  		return;
  
  	drv = to_scsi_driver(dev->driver);
  	if (try_module_get(drv->owner)) {
  		if (drv->rescan)
  			drv->rescan(dev);
  		module_put(drv->owner);
  	}
  }
  EXPORT_SYMBOL(scsi_rescan_device);
  
  static void __scsi_scan_target(struct device *parent, unsigned int channel,
  		unsigned int id, unsigned int lun, int rescan)
  {
  	struct Scsi_Host *shost = dev_to_shost(parent);
  	int bflags = 0;
  	int res;
  	struct scsi_target *starget;
  
  	if (shost->this_id == id)
  		/*
  		 * Don't scan the host adapter
  		 */
  		return;
  
  	starget = scsi_alloc_target(parent, channel, id);
  	if (!starget)
  		return;
  	scsi_autopm_get_target(starget);
  
  	if (lun != SCAN_WILD_CARD) {
  		/*
  		 * Scan for a specific host/chan/id/lun.
  		 */
  		scsi_probe_and_add_lun(starget, lun, NULL, NULL, rescan, NULL);
  		goto out_reap;
  	}
  
  	/*
  	 * Scan LUN 0, if there is some response, scan further. Ideally, we
  	 * would not configure LUN 0 until all LUNs are scanned.
  	 */
  	res = scsi_probe_and_add_lun(starget, 0, &bflags, NULL, rescan, NULL);
  	if (res == SCSI_SCAN_LUN_PRESENT || res == SCSI_SCAN_TARGET_PRESENT) {
  		if (scsi_report_lun_scan(starget, bflags, rescan) != 0)
  			/*
  			 * The REPORT LUN did not scan the target,
  			 * do a sequential scan.
  			 */
  			scsi_sequential_lun_scan(starget, bflags,
  						 starget->scsi_level, rescan);
  	}
  
   out_reap:
  	scsi_autopm_put_target(starget);
  	/* now determine if the target has any children at all
  	 * and if not, nuke it */
  	scsi_target_reap(starget);
  
  	put_device(&starget->dev);
  }
  
  /**
   * scsi_scan_target - scan a target id, possibly including all LUNs on the target.
   * @parent:	host to scan
   * @channel:	channel to scan
   * @id:		target id to scan
   * @lun:	Specific LUN to scan or SCAN_WILD_CARD
   * @rescan:	passed to LUN scanning routines
   *
   * Description:
   *     Scan the target id on @parent, @channel, and @id. Scan at least LUN 0,
   *     and possibly all LUNs on the target id.
   *
   *     First try a REPORT LUN scan, if that does not scan the target, do a
   *     sequential scan of LUNs on the target id.
   **/
  void scsi_scan_target(struct device *parent, unsigned int channel,
  		      unsigned int id, unsigned int lun, int rescan)
  {
  	struct Scsi_Host *shost = dev_to_shost(parent);
  
  	if (strncmp(scsi_scan_type, "none", 4) == 0)
  		return;
  
  	mutex_lock(&shost->scan_mutex);
  	if (!shost->async_scan)
  		scsi_complete_async_scans();
  
  	if (scsi_host_scan_allowed(shost) && scsi_autopm_get_host(shost) == 0) {
  		__scsi_scan_target(parent, channel, id, lun, rescan);
  		scsi_autopm_put_host(shost);
  	}
  	mutex_unlock(&shost->scan_mutex);
  }
  EXPORT_SYMBOL(scsi_scan_target);
  
  static void scsi_scan_channel(struct Scsi_Host *shost, unsigned int channel,
  			      unsigned int id, unsigned int lun, int rescan)
  {
  	uint order_id;
  
  	if (id == SCAN_WILD_CARD)
  		for (id = 0; id < shost->max_id; ++id) {
  			/*
  			 * XXX adapter drivers when possible (FCP, iSCSI)
  			 * could modify max_id to match the current max,
  			 * not the absolute max.
  			 *
  			 * XXX add a shost id iterator, so for example,
  			 * the FC ID can be the same as a target id
  			 * without a huge overhead of sparse id's.
  			 */
  			if (shost->reverse_ordering)
  				/*
  				 * Scan from high to low id.
  				 */
  				order_id = shost->max_id - id - 1;
  			else
  				order_id = id;
  			__scsi_scan_target(&shost->shost_gendev, channel,
  					order_id, lun, rescan);
  		}
  	else
  		__scsi_scan_target(&shost->shost_gendev, channel,
  				id, lun, rescan);
  }
  
  int scsi_scan_host_selected(struct Scsi_Host *shost, unsigned int channel,
  			    unsigned int id, unsigned int lun, int rescan)
  {
  	SCSI_LOG_SCAN_BUS(3, shost_printk (KERN_INFO, shost,
  		"%s: <%u:%u:%u>\n",
  		__func__, channel, id, lun));
  
  	if (((channel != SCAN_WILD_CARD) && (channel > shost->max_channel)) ||
  	    ((id != SCAN_WILD_CARD) && (id >= shost->max_id)) ||
  	    ((lun != SCAN_WILD_CARD) && (lun > shost->max_lun)))
  		return -EINVAL;
  
  	mutex_lock(&shost->scan_mutex);
  	if (!shost->async_scan)
  		scsi_complete_async_scans();
  
  	if (scsi_host_scan_allowed(shost) && scsi_autopm_get_host(shost) == 0) {
  		if (channel == SCAN_WILD_CARD)
  			for (channel = 0; channel <= shost->max_channel;
  			     channel++)
  				scsi_scan_channel(shost, channel, id, lun,
  						  rescan);
  		else
  			scsi_scan_channel(shost, channel, id, lun, rescan);
  		scsi_autopm_put_host(shost);
  	}
  	mutex_unlock(&shost->scan_mutex);
  
  	return 0;
  }
  
  static void scsi_sysfs_add_devices(struct Scsi_Host *shost)
  {
  	struct scsi_device *sdev;
  	shost_for_each_device(sdev, shost) {
  		if (!scsi_host_scan_allowed(shost) ||
  		    scsi_sysfs_add_sdev(sdev) != 0)
  			__scsi_remove_device(sdev);
  	}
  }
  
  /**
   * scsi_prep_async_scan - prepare for an async scan
   * @shost: the host which will be scanned
   * Returns: a cookie to be passed to scsi_finish_async_scan()
   *
   * Tells the midlayer this host is going to do an asynchronous scan.
   * It reserves the host's position in the scanning list and ensures
   * that other asynchronous scans started after this one won't affect the
   * ordering of the discovered devices.
   */
  static struct async_scan_data *scsi_prep_async_scan(struct Scsi_Host *shost)
  {
  	struct async_scan_data *data;
  	unsigned long flags;
  
  	if (strncmp(scsi_scan_type, "sync", 4) == 0)
  		return NULL;
  
  	if (shost->async_scan) {
  		printk("%s called twice for host %d", __func__,
  				shost->host_no);
  		dump_stack();
  		return NULL;
  	}
  
  	data = kmalloc(sizeof(*data), GFP_KERNEL);
  	if (!data)
  		goto err;
  	data->shost = scsi_host_get(shost);
  	if (!data->shost)
  		goto err;
  	init_completion(&data->prev_finished);
  
  	mutex_lock(&shost->scan_mutex);
  	spin_lock_irqsave(shost->host_lock, flags);
  	shost->async_scan = 1;
  	spin_unlock_irqrestore(shost->host_lock, flags);
  	mutex_unlock(&shost->scan_mutex);
  
  	spin_lock(&async_scan_lock);
  	if (list_empty(&scanning_hosts))
  		complete(&data->prev_finished);
  	list_add_tail(&data->list, &scanning_hosts);
  	spin_unlock(&async_scan_lock);
  
  	return data;
  
   err:
  	kfree(data);
  	return NULL;
  }
  
  /**
   * scsi_finish_async_scan - asynchronous scan has finished
   * @data: cookie returned from earlier call to scsi_prep_async_scan()
   *
   * All the devices currently attached to this host have been found.
   * This function announces all the devices it has found to the rest
   * of the system.
   */
  static void scsi_finish_async_scan(struct async_scan_data *data)
  {
  	struct Scsi_Host *shost;
  	unsigned long flags;
  
  	if (!data)
  		return;
  
  	shost = data->shost;
  
  	mutex_lock(&shost->scan_mutex);
  
  	if (!shost->async_scan) {
  		printk("%s called twice for host %d", __func__,
  				shost->host_no);
  		dump_stack();
  		mutex_unlock(&shost->scan_mutex);
  		return;
  	}
  
  	wait_for_completion(&data->prev_finished);
  
  	scsi_sysfs_add_devices(shost);
  
  	spin_lock_irqsave(shost->host_lock, flags);
  	shost->async_scan = 0;
  	spin_unlock_irqrestore(shost->host_lock, flags);
  
  	mutex_unlock(&shost->scan_mutex);
  
  	spin_lock(&async_scan_lock);
  	list_del(&data->list);
  	if (!list_empty(&scanning_hosts)) {
  		struct async_scan_data *next = list_entry(scanning_hosts.next,
  				struct async_scan_data, list);
  		complete(&next->prev_finished);
  	}
  	spin_unlock(&async_scan_lock);
  
  	scsi_host_put(shost);
  	kfree(data);
  }
  
  static void do_scsi_scan_host(struct Scsi_Host *shost)
  {
  	if (shost->hostt->scan_finished) {
  		unsigned long start = jiffies;
  		if (shost->hostt->scan_start)
  			shost->hostt->scan_start(shost);
  
  		while (!shost->hostt->scan_finished(shost, jiffies - start))
  			msleep(10);
  	} else {
  		scsi_scan_host_selected(shost, SCAN_WILD_CARD, SCAN_WILD_CARD,
  				SCAN_WILD_CARD, 0);
  	}
  }
  
  static int do_scan_async(void *_data)
  {
  	struct async_scan_data *data = _data;
  	struct Scsi_Host *shost = data->shost;
  
  	do_scsi_scan_host(shost);
  	scsi_finish_async_scan(data);
  	scsi_autopm_put_host(shost);
  	return 0;
  }
  
  /**
   * scsi_scan_host - scan the given adapter
   * @shost:	adapter to scan
   **/
  void scsi_scan_host(struct Scsi_Host *shost)
  {
  	struct task_struct *p;
  	struct async_scan_data *data;
  
  	if (strncmp(scsi_scan_type, "none", 4) == 0)
  		return;
  	if (scsi_autopm_get_host(shost) < 0)
  		return;
  
  	data = scsi_prep_async_scan(shost);
  	if (!data) {
  		do_scsi_scan_host(shost);
  		scsi_autopm_put_host(shost);
  		return;
  	}
  
  	p = kthread_run(do_scan_async, data, "scsi_scan_%d", shost->host_no);
  	if (IS_ERR(p))
  		do_scan_async(data);
  	/* scsi_autopm_put_host(shost) is called in do_scan_async() */
  }
  EXPORT_SYMBOL(scsi_scan_host);
  
  void scsi_forget_host(struct Scsi_Host *shost)
  {
  	struct scsi_device *sdev;
  	unsigned long flags;
  
   restart:
  	spin_lock_irqsave(shost->host_lock, flags);
  	list_for_each_entry(sdev, &shost->__devices, siblings) {
  		if (sdev->sdev_state == SDEV_DEL)
  			continue;
  		spin_unlock_irqrestore(shost->host_lock, flags);
  		__scsi_remove_device(sdev);
  		goto restart;
  	}
  	spin_unlock_irqrestore(shost->host_lock, flags);
  }
  
  /**
   * scsi_get_host_dev - Create a scsi_device that points to the host adapter itself
   * @shost: Host that needs a scsi_device
   *
   * Lock status: None assumed.
   *
   * Returns:     The scsi_device or NULL
   *
   * Notes:
   *	Attach a single scsi_device to the Scsi_Host - this should
   *	be made to look like a "pseudo-device" that points to the
   *	HA itself.
   *
   *	Note - this device is not accessible from any high-level
   *	drivers (including generics), which is probably not
   *	optimal.  We can add hooks later to attach.
   */
  struct scsi_device *scsi_get_host_dev(struct Scsi_Host *shost)
  {
  	struct scsi_device *sdev = NULL;
  	struct scsi_target *starget;
  
  	mutex_lock(&shost->scan_mutex);
  	if (!scsi_host_scan_allowed(shost))
  		goto out;
  	starget = scsi_alloc_target(&shost->shost_gendev, 0, shost->this_id);
  	if (!starget)
  		goto out;
  
  	sdev = scsi_alloc_sdev(starget, 0, NULL);
  	if (sdev)
  		sdev->borken = 0;
  	else
  		scsi_target_reap(starget);
  	put_device(&starget->dev);
   out:
  	mutex_unlock(&shost->scan_mutex);
  	return sdev;
  }
  EXPORT_SYMBOL(scsi_get_host_dev);
  
  /**
   * scsi_free_host_dev - Free a scsi_device that points to the host adapter itself
   * @sdev: Host device to be freed
   *
   * Lock status: None assumed.
   *
   * Returns:     Nothing
   */
  void scsi_free_host_dev(struct scsi_device *sdev)
  {
  	BUG_ON(sdev->id != sdev->host->this_id);
  
  	__scsi_remove_device(sdev);
  }
  EXPORT_SYMBOL(scsi_free_host_dev);
  
  