xref: /openbmc/linux/drivers/scsi/scsi.c (revision 5d0e4d78)
1 /*
2  *  scsi.c Copyright (C) 1992 Drew Eckhardt
3  *         Copyright (C) 1993, 1994, 1995, 1999 Eric Youngdale
4  *         Copyright (C) 2002, 2003 Christoph Hellwig
5  *
6  *  generic mid-level SCSI driver
7  *      Initial versions: Drew Eckhardt
8  *      Subsequent revisions: Eric Youngdale
9  *
10  *  <drew@colorado.edu>
11  *
12  *  Bug correction thanks go to :
13  *      Rik Faith <faith@cs.unc.edu>
14  *      Tommy Thorn <tthorn>
15  *      Thomas Wuensche <tw@fgb1.fgb.mw.tu-muenchen.de>
16  *
17  *  Modified by Eric Youngdale eric@andante.org or ericy@gnu.ai.mit.edu to
18  *  add scatter-gather, multiple outstanding request, and other
19  *  enhancements.
20  *
21  *  Native multichannel, wide scsi, /proc/scsi and hot plugging
22  *  support added by Michael Neuffer <mike@i-connect.net>
23  *
24  *  Added request_module("scsi_hostadapter") for kerneld:
25  *  (Put an "alias scsi_hostadapter your_hostadapter" in /etc/modprobe.conf)
26  *  Bjorn Ekwall  <bj0rn@blox.se>
27  *  (changed to kmod)
28  *
29  *  Major improvements to the timeout, abort, and reset processing,
30  *  as well as performance modifications for large queue depths by
31  *  Leonard N. Zubkoff <lnz@dandelion.com>
32  *
33  *  Converted cli() code to spinlocks, Ingo Molnar
34  *
35  *  Jiffies wrap fixes (host->resetting), 3 Dec 1998 Andrea Arcangeli
36  *
37  *  out_of_space hacks, D. Gilbert (dpg) 990608
38  */
39 
40 #include <linux/module.h>
41 #include <linux/moduleparam.h>
42 #include <linux/kernel.h>
43 #include <linux/timer.h>
44 #include <linux/string.h>
45 #include <linux/slab.h>
46 #include <linux/blkdev.h>
47 #include <linux/delay.h>
48 #include <linux/init.h>
49 #include <linux/completion.h>
50 #include <linux/unistd.h>
51 #include <linux/spinlock.h>
52 #include <linux/kmod.h>
53 #include <linux/interrupt.h>
54 #include <linux/notifier.h>
55 #include <linux/cpu.h>
56 #include <linux/mutex.h>
57 #include <linux/async.h>
58 #include <asm/unaligned.h>
59 
60 #include <scsi/scsi.h>
61 #include <scsi/scsi_cmnd.h>
62 #include <scsi/scsi_dbg.h>
63 #include <scsi/scsi_device.h>
64 #include <scsi/scsi_driver.h>
65 #include <scsi/scsi_eh.h>
66 #include <scsi/scsi_host.h>
67 #include <scsi/scsi_tcq.h>
68 
69 #include "scsi_priv.h"
70 #include "scsi_logging.h"
71 
72 #define CREATE_TRACE_POINTS
73 #include <trace/events/scsi.h>
74 
75 /*
76  * Definitions and constants.
77  */
78 
79 /*
80  * Note - the initial logging level can be set here to log events at boot time.
81  * After the system is up, you may enable logging via the /proc interface.
82  */
83 unsigned int scsi_logging_level;
84 #if defined(CONFIG_SCSI_LOGGING)
85 EXPORT_SYMBOL(scsi_logging_level);
86 #endif
87 
88 /* sd, scsi core and power management need to coordinate flushing async actions */
89 ASYNC_DOMAIN(scsi_sd_probe_domain);
90 EXPORT_SYMBOL(scsi_sd_probe_domain);
91 
92 /*
93  * Separate domain (from scsi_sd_probe_domain) to maximize the benefit of
94  * asynchronous system resume operations.  It is marked 'exclusive' to avoid
95  * being included in the async_synchronize_full() that is invoked by
96  * dpm_resume()
97  */
98 ASYNC_DOMAIN_EXCLUSIVE(scsi_sd_pm_domain);
99 EXPORT_SYMBOL(scsi_sd_pm_domain);
100 
101 /**
102  * scsi_put_command - Free a scsi command block
103  * @cmd: command block to free
104  *
105  * Returns:	Nothing.
106  *
107  * Notes:	The command must not belong to any lists.
108  */
109 void scsi_put_command(struct scsi_cmnd *cmd)
110 {
111 	scsi_del_cmd_from_list(cmd);
112 	BUG_ON(delayed_work_pending(&cmd->abort_work));
113 }
114 
115 #ifdef CONFIG_SCSI_LOGGING
116 void scsi_log_send(struct scsi_cmnd *cmd)
117 {
118 	unsigned int level;
119 
120 	/*
121 	 * If ML QUEUE log level is greater than or equal to:
122 	 *
123 	 * 1: nothing (match completion)
124 	 *
125 	 * 2: log opcode + command of all commands + cmd address
126 	 *
127 	 * 3: same as 2
128 	 *
129 	 * 4: same as 3
130 	 */
131 	if (unlikely(scsi_logging_level)) {
132 		level = SCSI_LOG_LEVEL(SCSI_LOG_MLQUEUE_SHIFT,
133 				       SCSI_LOG_MLQUEUE_BITS);
134 		if (level > 1) {
135 			scmd_printk(KERN_INFO, cmd,
136 				    "Send: scmd 0x%p\n", cmd);
137 			scsi_print_command(cmd);
138 		}
139 	}
140 }
141 
142 void scsi_log_completion(struct scsi_cmnd *cmd, int disposition)
143 {
144 	unsigned int level;
145 
146 	/*
147 	 * If ML COMPLETE log level is greater than or equal to:
148 	 *
149 	 * 1: log disposition, result, opcode + command, and conditionally
150 	 * sense data for failures or non SUCCESS dispositions.
151 	 *
152 	 * 2: same as 1 but for all command completions.
153 	 *
154 	 * 3: same as 2
155 	 *
156 	 * 4: same as 3 plus dump extra junk
157 	 */
158 	if (unlikely(scsi_logging_level)) {
159 		level = SCSI_LOG_LEVEL(SCSI_LOG_MLCOMPLETE_SHIFT,
160 				       SCSI_LOG_MLCOMPLETE_BITS);
161 		if (((level > 0) && (cmd->result || disposition != SUCCESS)) ||
162 		    (level > 1)) {
163 			scsi_print_result(cmd, "Done", disposition);
164 			scsi_print_command(cmd);
165 			if (status_byte(cmd->result) & CHECK_CONDITION)
166 				scsi_print_sense(cmd);
167 			if (level > 3)
168 				scmd_printk(KERN_INFO, cmd,
169 					    "scsi host busy %d failed %d\n",
170 					    atomic_read(&cmd->device->host->host_busy),
171 					    cmd->device->host->host_failed);
172 		}
173 	}
174 }
175 #endif
176 
177 /**
178  * scsi_cmd_get_serial - Assign a serial number to a command
179  * @host: the scsi host
180  * @cmd: command to assign serial number to
181  *
182  * Description: a serial number identifies a request for error recovery
183  * and debugging purposes.  Protected by the Host_Lock of host.
184  */
185 void scsi_cmd_get_serial(struct Scsi_Host *host, struct scsi_cmnd *cmd)
186 {
187 	cmd->serial_number = host->cmd_serial_number++;
188 	if (cmd->serial_number == 0)
189 		cmd->serial_number = host->cmd_serial_number++;
190 }
191 EXPORT_SYMBOL(scsi_cmd_get_serial);
192 
193 /**
194  * scsi_finish_command - cleanup and pass command back to upper layer
195  * @cmd: the command
196  *
197  * Description: Pass command off to upper layer for finishing of I/O
198  *              request, waking processes that are waiting on results,
199  *              etc.
200  */
201 void scsi_finish_command(struct scsi_cmnd *cmd)
202 {
203 	struct scsi_device *sdev = cmd->device;
204 	struct scsi_target *starget = scsi_target(sdev);
205 	struct Scsi_Host *shost = sdev->host;
206 	struct scsi_driver *drv;
207 	unsigned int good_bytes;
208 
209 	scsi_device_unbusy(sdev);
210 
211 	/*
212 	 * Clear the flags that say that the device/target/host is no longer
213 	 * capable of accepting new commands.
214 	 */
215 	if (atomic_read(&shost->host_blocked))
216 		atomic_set(&shost->host_blocked, 0);
217 	if (atomic_read(&starget->target_blocked))
218 		atomic_set(&starget->target_blocked, 0);
219 	if (atomic_read(&sdev->device_blocked))
220 		atomic_set(&sdev->device_blocked, 0);
221 
222 	/*
223 	 * If we have valid sense information, then some kind of recovery
224 	 * must have taken place.  Make a note of this.
225 	 */
226 	if (SCSI_SENSE_VALID(cmd))
227 		cmd->result |= (DRIVER_SENSE << 24);
228 
229 	SCSI_LOG_MLCOMPLETE(4, sdev_printk(KERN_INFO, sdev,
230 				"Notifying upper driver of completion "
231 				"(result %x)\n", cmd->result));
232 
233 	good_bytes = scsi_bufflen(cmd);
234         if (!blk_rq_is_passthrough(cmd->request)) {
235 		int old_good_bytes = good_bytes;
236 		drv = scsi_cmd_to_driver(cmd);
237 		if (drv->done)
238 			good_bytes = drv->done(cmd);
239 		/*
240 		 * USB may not give sense identifying bad sector and
241 		 * simply return a residue instead, so subtract off the
242 		 * residue if drv->done() error processing indicates no
243 		 * change to the completion length.
244 		 */
245 		if (good_bytes == old_good_bytes)
246 			good_bytes -= scsi_get_resid(cmd);
247 	}
248 	scsi_io_completion(cmd, good_bytes);
249 }
250 
251 /**
252  * scsi_change_queue_depth - change a device's queue depth
253  * @sdev: SCSI Device in question
254  * @depth: number of commands allowed to be queued to the driver
255  *
256  * Sets the device queue depth and returns the new value.
257  */
258 int scsi_change_queue_depth(struct scsi_device *sdev, int depth)
259 {
260 	if (depth > 0) {
261 		sdev->queue_depth = depth;
262 		wmb();
263 	}
264 
265 	if (sdev->request_queue)
266 		blk_set_queue_depth(sdev->request_queue, depth);
267 
268 	return sdev->queue_depth;
269 }
270 EXPORT_SYMBOL(scsi_change_queue_depth);
271 
272 /**
273  * scsi_track_queue_full - track QUEUE_FULL events to adjust queue depth
274  * @sdev: SCSI Device in question
275  * @depth: Current number of outstanding SCSI commands on this device,
276  *         not counting the one returned as QUEUE_FULL.
277  *
278  * Description:	This function will track successive QUEUE_FULL events on a
279  * 		specific SCSI device to determine if and when there is a
280  * 		need to adjust the queue depth on the device.
281  *
282  * Returns:	0 - No change needed, >0 - Adjust queue depth to this new depth,
283  * 		-1 - Drop back to untagged operation using host->cmd_per_lun
284  * 			as the untagged command depth
285  *
286  * Lock Status:	None held on entry
287  *
288  * Notes:	Low level drivers may call this at any time and we will do
289  * 		"The Right Thing."  We are interrupt context safe.
290  */
291 int scsi_track_queue_full(struct scsi_device *sdev, int depth)
292 {
293 
294 	/*
295 	 * Don't let QUEUE_FULLs on the same
296 	 * jiffies count, they could all be from
297 	 * same event.
298 	 */
299 	if ((jiffies >> 4) == (sdev->last_queue_full_time >> 4))
300 		return 0;
301 
302 	sdev->last_queue_full_time = jiffies;
303 	if (sdev->last_queue_full_depth != depth) {
304 		sdev->last_queue_full_count = 1;
305 		sdev->last_queue_full_depth = depth;
306 	} else {
307 		sdev->last_queue_full_count++;
308 	}
309 
310 	if (sdev->last_queue_full_count <= 10)
311 		return 0;
312 
313 	return scsi_change_queue_depth(sdev, depth);
314 }
315 EXPORT_SYMBOL(scsi_track_queue_full);
316 
317 /**
318  * scsi_vpd_inquiry - Request a device provide us with a VPD page
319  * @sdev: The device to ask
320  * @buffer: Where to put the result
321  * @page: Which Vital Product Data to return
322  * @len: The length of the buffer
323  *
324  * This is an internal helper function.  You probably want to use
325  * scsi_get_vpd_page instead.
326  *
327  * Returns size of the vpd page on success or a negative error number.
328  */
329 static int scsi_vpd_inquiry(struct scsi_device *sdev, unsigned char *buffer,
330 							u8 page, unsigned len)
331 {
332 	int result;
333 	unsigned char cmd[16];
334 
335 	if (len < 4)
336 		return -EINVAL;
337 
338 	cmd[0] = INQUIRY;
339 	cmd[1] = 1;		/* EVPD */
340 	cmd[2] = page;
341 	cmd[3] = len >> 8;
342 	cmd[4] = len & 0xff;
343 	cmd[5] = 0;		/* Control byte */
344 
345 	/*
346 	 * I'm not convinced we need to try quite this hard to get VPD, but
347 	 * all the existing users tried this hard.
348 	 */
349 	result = scsi_execute_req(sdev, cmd, DMA_FROM_DEVICE, buffer,
350 				  len, NULL, 30 * HZ, 3, NULL);
351 	if (result)
352 		return -EIO;
353 
354 	/* Sanity check that we got the page back that we asked for */
355 	if (buffer[1] != page)
356 		return -EIO;
357 
358 	return get_unaligned_be16(&buffer[2]) + 4;
359 }
360 
361 /**
362  * scsi_get_vpd_page - Get Vital Product Data from a SCSI device
363  * @sdev: The device to ask
364  * @page: Which Vital Product Data to return
365  * @buf: where to store the VPD
366  * @buf_len: number of bytes in the VPD buffer area
367  *
368  * SCSI devices may optionally supply Vital Product Data.  Each 'page'
369  * of VPD is defined in the appropriate SCSI document (eg SPC, SBC).
370  * If the device supports this VPD page, this routine returns a pointer
371  * to a buffer containing the data from that page.  The caller is
372  * responsible for calling kfree() on this pointer when it is no longer
373  * needed.  If we cannot retrieve the VPD page this routine returns %NULL.
374  */
375 int scsi_get_vpd_page(struct scsi_device *sdev, u8 page, unsigned char *buf,
376 		      int buf_len)
377 {
378 	int i, result;
379 
380 	if (sdev->skip_vpd_pages)
381 		goto fail;
382 
383 	/* Ask for all the pages supported by this device */
384 	result = scsi_vpd_inquiry(sdev, buf, 0, buf_len);
385 	if (result < 4)
386 		goto fail;
387 
388 	/* If the user actually wanted this page, we can skip the rest */
389 	if (page == 0)
390 		return 0;
391 
392 	for (i = 4; i < min(result, buf_len); i++)
393 		if (buf[i] == page)
394 			goto found;
395 
396 	if (i < result && i >= buf_len)
397 		/* ran off the end of the buffer, give us benefit of doubt */
398 		goto found;
399 	/* The device claims it doesn't support the requested page */
400 	goto fail;
401 
402  found:
403 	result = scsi_vpd_inquiry(sdev, buf, page, buf_len);
404 	if (result < 0)
405 		goto fail;
406 
407 	return 0;
408 
409  fail:
410 	return -EINVAL;
411 }
412 EXPORT_SYMBOL_GPL(scsi_get_vpd_page);
413 
414 /**
415  * scsi_attach_vpd - Attach Vital Product Data to a SCSI device structure
416  * @sdev: The device to ask
417  *
418  * Attach the 'Device Identification' VPD page (0x83) and the
419  * 'Unit Serial Number' VPD page (0x80) to a SCSI device
420  * structure. This information can be used to identify the device
421  * uniquely.
422  */
423 void scsi_attach_vpd(struct scsi_device *sdev)
424 {
425 	int result, i;
426 	int vpd_len = SCSI_VPD_PG_LEN;
427 	int pg80_supported = 0;
428 	int pg83_supported = 0;
429 	unsigned char __rcu *vpd_buf, *orig_vpd_buf = NULL;
430 
431 	if (!scsi_device_supports_vpd(sdev))
432 		return;
433 
434 retry_pg0:
435 	vpd_buf = kmalloc(vpd_len, GFP_KERNEL);
436 	if (!vpd_buf)
437 		return;
438 
439 	/* Ask for all the pages supported by this device */
440 	result = scsi_vpd_inquiry(sdev, vpd_buf, 0, vpd_len);
441 	if (result < 0) {
442 		kfree(vpd_buf);
443 		return;
444 	}
445 	if (result > vpd_len) {
446 		vpd_len = result;
447 		kfree(vpd_buf);
448 		goto retry_pg0;
449 	}
450 
451 	for (i = 4; i < result; i++) {
452 		if (vpd_buf[i] == 0x80)
453 			pg80_supported = 1;
454 		if (vpd_buf[i] == 0x83)
455 			pg83_supported = 1;
456 	}
457 	kfree(vpd_buf);
458 	vpd_len = SCSI_VPD_PG_LEN;
459 
460 	if (pg80_supported) {
461 retry_pg80:
462 		vpd_buf = kmalloc(vpd_len, GFP_KERNEL);
463 		if (!vpd_buf)
464 			return;
465 
466 		result = scsi_vpd_inquiry(sdev, vpd_buf, 0x80, vpd_len);
467 		if (result < 0) {
468 			kfree(vpd_buf);
469 			return;
470 		}
471 		if (result > vpd_len) {
472 			vpd_len = result;
473 			kfree(vpd_buf);
474 			goto retry_pg80;
475 		}
476 		mutex_lock(&sdev->inquiry_mutex);
477 		orig_vpd_buf = sdev->vpd_pg80;
478 		sdev->vpd_pg80_len = result;
479 		rcu_assign_pointer(sdev->vpd_pg80, vpd_buf);
480 		mutex_unlock(&sdev->inquiry_mutex);
481 		synchronize_rcu();
482 		if (orig_vpd_buf) {
483 			kfree(orig_vpd_buf);
484 			orig_vpd_buf = NULL;
485 		}
486 		vpd_len = SCSI_VPD_PG_LEN;
487 	}
488 
489 	if (pg83_supported) {
490 retry_pg83:
491 		vpd_buf = kmalloc(vpd_len, GFP_KERNEL);
492 		if (!vpd_buf)
493 			return;
494 
495 		result = scsi_vpd_inquiry(sdev, vpd_buf, 0x83, vpd_len);
496 		if (result < 0) {
497 			kfree(vpd_buf);
498 			return;
499 		}
500 		if (result > vpd_len) {
501 			vpd_len = result;
502 			kfree(vpd_buf);
503 			goto retry_pg83;
504 		}
505 		mutex_lock(&sdev->inquiry_mutex);
506 		orig_vpd_buf = sdev->vpd_pg83;
507 		sdev->vpd_pg83_len = result;
508 		rcu_assign_pointer(sdev->vpd_pg83, vpd_buf);
509 		mutex_unlock(&sdev->inquiry_mutex);
510 		synchronize_rcu();
511 		if (orig_vpd_buf)
512 			kfree(orig_vpd_buf);
513 	}
514 }
515 
516 /**
517  * scsi_report_opcode - Find out if a given command opcode is supported
518  * @sdev:	scsi device to query
519  * @buffer:	scratch buffer (must be at least 20 bytes long)
520  * @len:	length of buffer
521  * @opcode:	opcode for command to look up
522  *
523  * Uses the REPORT SUPPORTED OPERATION CODES to look up the given
524  * opcode. Returns -EINVAL if RSOC fails, 0 if the command opcode is
525  * unsupported and 1 if the device claims to support the command.
526  */
527 int scsi_report_opcode(struct scsi_device *sdev, unsigned char *buffer,
528 		       unsigned int len, unsigned char opcode)
529 {
530 	unsigned char cmd[16];
531 	struct scsi_sense_hdr sshdr;
532 	int result;
533 
534 	if (sdev->no_report_opcodes || sdev->scsi_level < SCSI_SPC_3)
535 		return -EINVAL;
536 
537 	memset(cmd, 0, 16);
538 	cmd[0] = MAINTENANCE_IN;
539 	cmd[1] = MI_REPORT_SUPPORTED_OPERATION_CODES;
540 	cmd[2] = 1;		/* One command format */
541 	cmd[3] = opcode;
542 	put_unaligned_be32(len, &cmd[6]);
543 	memset(buffer, 0, len);
544 
545 	result = scsi_execute_req(sdev, cmd, DMA_FROM_DEVICE, buffer, len,
546 				  &sshdr, 30 * HZ, 3, NULL);
547 
548 	if (result && scsi_sense_valid(&sshdr) &&
549 	    sshdr.sense_key == ILLEGAL_REQUEST &&
550 	    (sshdr.asc == 0x20 || sshdr.asc == 0x24) && sshdr.ascq == 0x00)
551 		return -EINVAL;
552 
553 	if ((buffer[1] & 3) == 3) /* Command supported */
554 		return 1;
555 
556 	return 0;
557 }
558 EXPORT_SYMBOL(scsi_report_opcode);
559 
560 /**
561  * scsi_device_get  -  get an additional reference to a scsi_device
562  * @sdev:	device to get a reference to
563  *
564  * Description: Gets a reference to the scsi_device and increments the use count
565  * of the underlying LLDD module.  You must hold host_lock of the
566  * parent Scsi_Host or already have a reference when calling this.
567  *
568  * This will fail if a device is deleted or cancelled, or when the LLD module
569  * is in the process of being unloaded.
570  */
571 int scsi_device_get(struct scsi_device *sdev)
572 {
573 	if (sdev->sdev_state == SDEV_DEL || sdev->sdev_state == SDEV_CANCEL)
574 		goto fail;
575 	if (!get_device(&sdev->sdev_gendev))
576 		goto fail;
577 	if (!try_module_get(sdev->host->hostt->module))
578 		goto fail_put_device;
579 	return 0;
580 
581 fail_put_device:
582 	put_device(&sdev->sdev_gendev);
583 fail:
584 	return -ENXIO;
585 }
586 EXPORT_SYMBOL(scsi_device_get);
587 
588 /**
589  * scsi_device_put  -  release a reference to a scsi_device
590  * @sdev:	device to release a reference on.
591  *
592  * Description: Release a reference to the scsi_device and decrements the use
593  * count of the underlying LLDD module.  The device is freed once the last
594  * user vanishes.
595  */
596 void scsi_device_put(struct scsi_device *sdev)
597 {
598 	module_put(sdev->host->hostt->module);
599 	put_device(&sdev->sdev_gendev);
600 }
601 EXPORT_SYMBOL(scsi_device_put);
602 
603 /* helper for shost_for_each_device, see that for documentation */
604 struct scsi_device *__scsi_iterate_devices(struct Scsi_Host *shost,
605 					   struct scsi_device *prev)
606 {
607 	struct list_head *list = (prev ? &prev->siblings : &shost->__devices);
608 	struct scsi_device *next = NULL;
609 	unsigned long flags;
610 
611 	spin_lock_irqsave(shost->host_lock, flags);
612 	while (list->next != &shost->__devices) {
613 		next = list_entry(list->next, struct scsi_device, siblings);
614 		/* skip devices that we can't get a reference to */
615 		if (!scsi_device_get(next))
616 			break;
617 		next = NULL;
618 		list = list->next;
619 	}
620 	spin_unlock_irqrestore(shost->host_lock, flags);
621 
622 	if (prev)
623 		scsi_device_put(prev);
624 	return next;
625 }
626 EXPORT_SYMBOL(__scsi_iterate_devices);
627 
628 /**
629  * starget_for_each_device  -  helper to walk all devices of a target
630  * @starget:	target whose devices we want to iterate over.
631  * @data:	Opaque passed to each function call.
632  * @fn:		Function to call on each device
633  *
634  * This traverses over each device of @starget.  The devices have
635  * a reference that must be released by scsi_host_put when breaking
636  * out of the loop.
637  */
638 void starget_for_each_device(struct scsi_target *starget, void *data,
639 		     void (*fn)(struct scsi_device *, void *))
640 {
641 	struct Scsi_Host *shost = dev_to_shost(starget->dev.parent);
642 	struct scsi_device *sdev;
643 
644 	shost_for_each_device(sdev, shost) {
645 		if ((sdev->channel == starget->channel) &&
646 		    (sdev->id == starget->id))
647 			fn(sdev, data);
648 	}
649 }
650 EXPORT_SYMBOL(starget_for_each_device);
651 
652 /**
653  * __starget_for_each_device - helper to walk all devices of a target (UNLOCKED)
654  * @starget:	target whose devices we want to iterate over.
655  * @data:	parameter for callback @fn()
656  * @fn:		callback function that is invoked for each device
657  *
658  * This traverses over each device of @starget.  It does _not_
659  * take a reference on the scsi_device, so the whole loop must be
660  * protected by shost->host_lock.
661  *
662  * Note:  The only reason why drivers would want to use this is because
663  * they need to access the device list in irq context.  Otherwise you
664  * really want to use starget_for_each_device instead.
665  **/
666 void __starget_for_each_device(struct scsi_target *starget, void *data,
667 			       void (*fn)(struct scsi_device *, void *))
668 {
669 	struct Scsi_Host *shost = dev_to_shost(starget->dev.parent);
670 	struct scsi_device *sdev;
671 
672 	__shost_for_each_device(sdev, shost) {
673 		if ((sdev->channel == starget->channel) &&
674 		    (sdev->id == starget->id))
675 			fn(sdev, data);
676 	}
677 }
678 EXPORT_SYMBOL(__starget_for_each_device);
679 
680 /**
681  * __scsi_device_lookup_by_target - find a device given the target (UNLOCKED)
682  * @starget:	SCSI target pointer
683  * @lun:	SCSI Logical Unit Number
684  *
685  * Description: Looks up the scsi_device with the specified @lun for a given
686  * @starget.  The returned scsi_device does not have an additional
687  * reference.  You must hold the host's host_lock over this call and
688  * any access to the returned scsi_device. A scsi_device in state
689  * SDEV_DEL is skipped.
690  *
691  * Note:  The only reason why drivers should use this is because
692  * they need to access the device list in irq context.  Otherwise you
693  * really want to use scsi_device_lookup_by_target instead.
694  **/
695 struct scsi_device *__scsi_device_lookup_by_target(struct scsi_target *starget,
696 						   u64 lun)
697 {
698 	struct scsi_device *sdev;
699 
700 	list_for_each_entry(sdev, &starget->devices, same_target_siblings) {
701 		if (sdev->sdev_state == SDEV_DEL)
702 			continue;
703 		if (sdev->lun ==lun)
704 			return sdev;
705 	}
706 
707 	return NULL;
708 }
709 EXPORT_SYMBOL(__scsi_device_lookup_by_target);
710 
711 /**
712  * scsi_device_lookup_by_target - find a device given the target
713  * @starget:	SCSI target pointer
714  * @lun:	SCSI Logical Unit Number
715  *
716  * Description: Looks up the scsi_device with the specified @lun for a given
717  * @starget.  The returned scsi_device has an additional reference that
718  * needs to be released with scsi_device_put once you're done with it.
719  **/
720 struct scsi_device *scsi_device_lookup_by_target(struct scsi_target *starget,
721 						 u64 lun)
722 {
723 	struct scsi_device *sdev;
724 	struct Scsi_Host *shost = dev_to_shost(starget->dev.parent);
725 	unsigned long flags;
726 
727 	spin_lock_irqsave(shost->host_lock, flags);
728 	sdev = __scsi_device_lookup_by_target(starget, lun);
729 	if (sdev && scsi_device_get(sdev))
730 		sdev = NULL;
731 	spin_unlock_irqrestore(shost->host_lock, flags);
732 
733 	return sdev;
734 }
735 EXPORT_SYMBOL(scsi_device_lookup_by_target);
736 
737 /**
738  * __scsi_device_lookup - find a device given the host (UNLOCKED)
739  * @shost:	SCSI host pointer
740  * @channel:	SCSI channel (zero if only one channel)
741  * @id:		SCSI target number (physical unit number)
742  * @lun:	SCSI Logical Unit Number
743  *
744  * Description: Looks up the scsi_device with the specified @channel, @id, @lun
745  * for a given host. The returned scsi_device does not have an additional
746  * reference.  You must hold the host's host_lock over this call and any access
747  * to the returned scsi_device.
748  *
749  * Note:  The only reason why drivers would want to use this is because
750  * they need to access the device list in irq context.  Otherwise you
751  * really want to use scsi_device_lookup instead.
752  **/
753 struct scsi_device *__scsi_device_lookup(struct Scsi_Host *shost,
754 		uint channel, uint id, u64 lun)
755 {
756 	struct scsi_device *sdev;
757 
758 	list_for_each_entry(sdev, &shost->__devices, siblings) {
759 		if (sdev->sdev_state == SDEV_DEL)
760 			continue;
761 		if (sdev->channel == channel && sdev->id == id &&
762 				sdev->lun ==lun)
763 			return sdev;
764 	}
765 
766 	return NULL;
767 }
768 EXPORT_SYMBOL(__scsi_device_lookup);
769 
770 /**
771  * scsi_device_lookup - find a device given the host
772  * @shost:	SCSI host pointer
773  * @channel:	SCSI channel (zero if only one channel)
774  * @id:		SCSI target number (physical unit number)
775  * @lun:	SCSI Logical Unit Number
776  *
777  * Description: Looks up the scsi_device with the specified @channel, @id, @lun
778  * for a given host.  The returned scsi_device has an additional reference that
779  * needs to be released with scsi_device_put once you're done with it.
780  **/
781 struct scsi_device *scsi_device_lookup(struct Scsi_Host *shost,
782 		uint channel, uint id, u64 lun)
783 {
784 	struct scsi_device *sdev;
785 	unsigned long flags;
786 
787 	spin_lock_irqsave(shost->host_lock, flags);
788 	sdev = __scsi_device_lookup(shost, channel, id, lun);
789 	if (sdev && scsi_device_get(sdev))
790 		sdev = NULL;
791 	spin_unlock_irqrestore(shost->host_lock, flags);
792 
793 	return sdev;
794 }
795 EXPORT_SYMBOL(scsi_device_lookup);
796 
797 MODULE_DESCRIPTION("SCSI core");
798 MODULE_LICENSE("GPL");
799 
800 module_param(scsi_logging_level, int, S_IRUGO|S_IWUSR);
801 MODULE_PARM_DESC(scsi_logging_level, "a bit mask of logging levels");
802 
803 bool scsi_use_blk_mq = true;
804 module_param_named(use_blk_mq, scsi_use_blk_mq, bool, S_IWUSR | S_IRUGO);
805 
806 static int __init init_scsi(void)
807 {
808 	int error;
809 
810 	error = scsi_init_queue();
811 	if (error)
812 		return error;
813 	error = scsi_init_procfs();
814 	if (error)
815 		goto cleanup_queue;
816 	error = scsi_init_devinfo();
817 	if (error)
818 		goto cleanup_procfs;
819 	error = scsi_init_hosts();
820 	if (error)
821 		goto cleanup_devlist;
822 	error = scsi_init_sysctl();
823 	if (error)
824 		goto cleanup_hosts;
825 	error = scsi_sysfs_register();
826 	if (error)
827 		goto cleanup_sysctl;
828 
829 	scsi_netlink_init();
830 
831 	printk(KERN_NOTICE "SCSI subsystem initialized\n");
832 	return 0;
833 
834 cleanup_sysctl:
835 	scsi_exit_sysctl();
836 cleanup_hosts:
837 	scsi_exit_hosts();
838 cleanup_devlist:
839 	scsi_exit_devinfo();
840 cleanup_procfs:
841 	scsi_exit_procfs();
842 cleanup_queue:
843 	scsi_exit_queue();
844 	printk(KERN_ERR "SCSI subsystem failed to initialize, error = %d\n",
845 	       -error);
846 	return error;
847 }
848 
849 static void __exit exit_scsi(void)
850 {
851 	scsi_netlink_exit();
852 	scsi_sysfs_unregister();
853 	scsi_exit_sysctl();
854 	scsi_exit_hosts();
855 	scsi_exit_devinfo();
856 	scsi_exit_procfs();
857 	scsi_exit_queue();
858 	async_unregister_domain(&scsi_sd_probe_domain);
859 }
860 
861 subsys_initcall(init_scsi);
862 module_exit(exit_scsi);
863