summaryrefslogtreecommitdiff
path: root/drivers/usb/storage/uas.c
blob: a33ead5dce2045d2abc18779c05c26b20a339bc0 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
/*
 * USB Attached SCSI
 * Note that this is not the same as the USB Mass Storage driver
 *
 * Copyright Matthew Wilcox for Intel Corp, 2010
 * Copyright Sarah Sharp for Intel Corp, 2010
 *
 * Distributed under the terms of the GNU GPL, version two.
 */

#include <linux/blkdev.h>
#include <linux/slab.h>
#include <linux/types.h>
#include <linux/module.h>
#include <linux/usb.h>
#include <linux/usb/storage.h>

#include <scsi/scsi.h>
#include <scsi/scsi_dbg.h>
#include <scsi/scsi_cmnd.h>
#include <scsi/scsi_device.h>
#include <scsi/scsi_host.h>
#include <scsi/scsi_tcq.h>

/* Common header for all IUs */
struct iu {
	__u8 iu_id;
	__u8 rsvd1;
	__be16 tag;
};

enum {
	IU_ID_COMMAND		= 0x01,
	IU_ID_STATUS		= 0x03,
	IU_ID_RESPONSE		= 0x04,
	IU_ID_TASK_MGMT		= 0x05,
	IU_ID_READ_READY	= 0x06,
	IU_ID_WRITE_READY	= 0x07,
};

struct command_iu {
	__u8 iu_id;
	__u8 rsvd1;
	__be16 tag;
	__u8 prio_attr;
	__u8 rsvd5;
	__u8 len;
	__u8 rsvd7;
	struct scsi_lun lun;
	__u8 cdb[16];	/* XXX: Overflow-checking tools may misunderstand */
};

/*
 * Also used for the Read Ready and Write Ready IUs since they have the
 * same first four bytes
 */
struct sense_iu {
	__u8 iu_id;
	__u8 rsvd1;
	__be16 tag;
	__be16 status_qual;
	__u8 status;
	__u8 rsvd7[7];
	__be16 len;
	__u8 sense[SCSI_SENSE_BUFFERSIZE];
};

/*
 * The r00-r01c specs define this version of the SENSE IU data structure.
 * It's still in use by several different firmware releases.
 */
struct sense_iu_old {
	__u8 iu_id;
	__u8 rsvd1;
	__be16 tag;
	__be16 len;
	__u8 status;
	__u8 service_response;
	__u8 sense[SCSI_SENSE_BUFFERSIZE];
};

enum {
	CMD_PIPE_ID		= 1,
	STATUS_PIPE_ID		= 2,
	DATA_IN_PIPE_ID		= 3,
	DATA_OUT_PIPE_ID	= 4,

	UAS_SIMPLE_TAG		= 0,
	UAS_HEAD_TAG		= 1,
	UAS_ORDERED_TAG		= 2,
	UAS_ACA			= 4,
};

struct uas_dev_info {
	struct usb_interface *intf;
	struct usb_device *udev;
	int qdepth;
	unsigned cmd_pipe, status_pipe, data_in_pipe, data_out_pipe;
	unsigned use_streams:1;
	unsigned uas_sense_old:1;
};

enum {
	ALLOC_STATUS_URB	= (1 << 0),
	SUBMIT_STATUS_URB	= (1 << 1),
	ALLOC_DATA_IN_URB	= (1 << 2),
	SUBMIT_DATA_IN_URB	= (1 << 3),
	ALLOC_DATA_OUT_URB	= (1 << 4),
	SUBMIT_DATA_OUT_URB	= (1 << 5),
	ALLOC_CMD_URB		= (1 << 6),
	SUBMIT_CMD_URB		= (1 << 7),
};

/* Overrides scsi_pointer */
struct uas_cmd_info {
	unsigned int state;
	unsigned int stream;
	struct urb *cmd_urb;
	struct urb *status_urb;
	struct urb *data_in_urb;
	struct urb *data_out_urb;
	struct list_head list;
};

/* I hate forward declarations, but I actually have a loop */
static int uas_submit_urbs(struct scsi_cmnd *cmnd,
				struct uas_dev_info *devinfo, gfp_t gfp);

static DEFINE_SPINLOCK(uas_work_lock);
static LIST_HEAD(uas_work_list);

static void uas_do_work(struct work_struct *work)
{
	struct uas_cmd_info *cmdinfo;
	struct list_head list;

	spin_lock_irq(&uas_work_lock);
	list_replace_init(&uas_work_list, &list);
	spin_unlock_irq(&uas_work_lock);

	list_for_each_entry(cmdinfo, &list, list) {
		struct scsi_pointer *scp = (void *)cmdinfo;
		struct scsi_cmnd *cmnd = container_of(scp,
							struct scsi_cmnd, SCp);
		uas_submit_urbs(cmnd, cmnd->device->hostdata, GFP_NOIO);
	}
}

static DECLARE_WORK(uas_work, uas_do_work);

static void uas_sense(struct urb *urb, struct scsi_cmnd *cmnd)
{
	struct sense_iu *sense_iu = urb->transfer_buffer;
	struct scsi_device *sdev = cmnd->device;

	if (urb->actual_length > 16) {
		unsigned len = be16_to_cpup(&sense_iu->len);
		if (len + 16 != urb->actual_length) {
			int newlen = min(len + 16, urb->actual_length) - 16;
			if (newlen < 0)
				newlen = 0;
			sdev_printk(KERN_INFO, sdev, "%s: urb length %d "
				"disagrees with IU sense data length %d, "
				"using %d bytes of sense data\n", __func__,
					urb->actual_length, len, newlen);
			len = newlen;
		}
		memcpy(cmnd->sense_buffer, sense_iu->sense, len);
	}

	cmnd->result = sense_iu->status;
	if (sdev->current_cmnd)
		sdev->current_cmnd = NULL;
	cmnd->scsi_done(cmnd);
	usb_free_urb(urb);
}

static void uas_sense_old(struct urb *urb, struct scsi_cmnd *cmnd)
{
	struct sense_iu_old *sense_iu = urb->transfer_buffer;
	struct scsi_device *sdev = cmnd->device;

	if (urb->actual_length > 8) {
		unsigned len = be16_to_cpup(&sense_iu->len) - 2;
		if (len + 8 != urb->actual_length) {
			int newlen = min(len + 8, urb->actual_length) - 8;
			if (newlen < 0)
				newlen = 0;
			sdev_printk(KERN_INFO, sdev, "%s: urb length %d "
				"disagrees with IU sense data length %d, "
				"using %d bytes of sense data\n", __func__,
					urb->actual_length, len, newlen);
			len = newlen;
		}
		memcpy(cmnd->sense_buffer, sense_iu->sense, len);
	}

	cmnd->result = sense_iu->status;
	if (sdev->current_cmnd)
		sdev->current_cmnd = NULL;
	cmnd->scsi_done(cmnd);
	usb_free_urb(urb);
}

static void uas_xfer_data(struct urb *urb, struct scsi_cmnd *cmnd,
							unsigned direction)
{
	struct uas_cmd_info *cmdinfo = (void *)&cmnd->SCp;
	int err;

	cmdinfo->state = direction | SUBMIT_STATUS_URB;
	err = uas_submit_urbs(cmnd, cmnd->device->hostdata, GFP_ATOMIC);
	if (err) {
		spin_lock(&uas_work_lock);
		list_add_tail(&cmdinfo->list, &uas_work_list);
		spin_unlock(&uas_work_lock);
		schedule_work(&uas_work);
	}
}

static void uas_stat_cmplt(struct urb *urb)
{
	struct iu *iu = urb->transfer_buffer;
	struct scsi_device *sdev = urb->context;
	struct uas_dev_info *devinfo = sdev->hostdata;
	struct scsi_cmnd *cmnd;
	u16 tag;

	if (urb->status) {
		dev_err(&urb->dev->dev, "URB BAD STATUS %d\n", urb->status);
		usb_free_urb(urb);
		return;
	}

	tag = be16_to_cpup(&iu->tag) - 1;
	if (sdev->current_cmnd)
		cmnd = sdev->current_cmnd;
	else
		cmnd = scsi_find_tag(sdev, tag);
	if (!cmnd)
		return;

	switch (iu->iu_id) {
	case IU_ID_STATUS:
		if (urb->actual_length < 16)
			devinfo->uas_sense_old = 1;
		if (devinfo->uas_sense_old)
			uas_sense_old(urb, cmnd);
		else
			uas_sense(urb, cmnd);
		break;
	case IU_ID_READ_READY:
		uas_xfer_data(urb, cmnd, SUBMIT_DATA_IN_URB);
		break;
	case IU_ID_WRITE_READY:
		uas_xfer_data(urb, cmnd, SUBMIT_DATA_OUT_URB);
		break;
	default:
		scmd_printk(KERN_ERR, cmnd,
			"Bogus IU (%d) received on status pipe\n", iu->iu_id);
	}
}

static void uas_data_cmplt(struct urb *urb)
{
	struct scsi_data_buffer *sdb = urb->context;
	sdb->resid = sdb->length - urb->actual_length;
	usb_free_urb(urb);
}

static struct urb *uas_alloc_data_urb(struct uas_dev_info *devinfo, gfp_t gfp,
				unsigned int pipe, u16 stream_id,
				struct scsi_data_buffer *sdb,
				enum dma_data_direction dir)
{
	struct usb_device *udev = devinfo->udev;
	struct urb *urb = usb_alloc_urb(0, gfp);

	if (!urb)
		goto out;
	usb_fill_bulk_urb(urb, udev, pipe, NULL, sdb->length, uas_data_cmplt,
									sdb);
	if (devinfo->use_streams)
		urb->stream_id = stream_id;
	urb->num_sgs = udev->bus->sg_tablesize ? sdb->table.nents : 0;
	urb->sg = sdb->table.sgl;
 out:
	return urb;
}

static struct urb *uas_alloc_sense_urb(struct uas_dev_info *devinfo, gfp_t gfp,
					struct scsi_cmnd *cmnd, u16 stream_id)
{
	struct usb_device *udev = devinfo->udev;
	struct urb *urb = usb_alloc_urb(0, gfp);
	struct sense_iu *iu;

	if (!urb)
		goto out;

	iu = kzalloc(sizeof(*iu), gfp);
	if (!iu)
		goto free;

	usb_fill_bulk_urb(urb, udev, devinfo->status_pipe, iu, sizeof(*iu),
						uas_stat_cmplt, cmnd->device);
	urb->stream_id = stream_id;
	urb->transfer_flags |= URB_FREE_BUFFER;
 out:
	return urb;
 free:
	usb_free_urb(urb);
	return NULL;
}

static struct urb *uas_alloc_cmd_urb(struct uas_dev_info *devinfo, gfp_t gfp,
					struct scsi_cmnd *cmnd, u16 stream_id)
{
	struct usb_device *udev = devinfo->udev;
	struct scsi_device *sdev = cmnd->device;
	struct urb *urb = usb_alloc_urb(0, gfp);
	struct command_iu *iu;
	int len;

	if (!urb)
		goto out;

	len = cmnd->cmd_len - 16;
	if (len < 0)
		len = 0;
	len = ALIGN(len, 4);
	iu = kzalloc(sizeof(*iu) + len, gfp);
	if (!iu)
		goto free;

	iu->iu_id = IU_ID_COMMAND;
	iu->tag = cpu_to_be16(stream_id);
	iu->prio_attr = UAS_SIMPLE_TAG;
	iu->len = len;
	int_to_scsilun(sdev->lun, &iu->lun);
	memcpy(iu->cdb, cmnd->cmnd, cmnd->cmd_len);

	usb_fill_bulk_urb(urb, udev, devinfo->cmd_pipe, iu, sizeof(*iu) + len,
							usb_free_urb, NULL);
	urb->transfer_flags |= URB_FREE_BUFFER;
 out:
	return urb;
 free:
	usb_free_urb(urb);
	return NULL;
}

/*
 * Why should I request the Status IU before sending the Command IU?  Spec
 * says to, but also says the device may receive them in any order.  Seems
 * daft to me.
 */

static int uas_submit_urbs(struct scsi_cmnd *cmnd,
					struct uas_dev_info *devinfo, gfp_t gfp)
{
	struct uas_cmd_info *cmdinfo = (void *)&cmnd->SCp;

	if (cmdinfo->state & ALLOC_STATUS_URB) {
		cmdinfo->status_urb = uas_alloc_sense_urb(devinfo, gfp, cmnd,
							  cmdinfo->stream);
		if (!cmdinfo->status_urb)
			return SCSI_MLQUEUE_DEVICE_BUSY;
		cmdinfo->state &= ~ALLOC_STATUS_URB;
	}

	if (cmdinfo->state & SUBMIT_STATUS_URB) {
		if (usb_submit_urb(cmdinfo->status_urb, gfp)) {
			scmd_printk(KERN_INFO, cmnd,
					"sense urb submission failure\n");
			return SCSI_MLQUEUE_DEVICE_BUSY;
		}
		cmdinfo->state &= ~SUBMIT_STATUS_URB;
	}

	if (cmdinfo->state & ALLOC_DATA_IN_URB) {
		cmdinfo->data_in_urb = uas_alloc_data_urb(devinfo, gfp,
					devinfo->data_in_pipe, cmdinfo->stream,
					scsi_in(cmnd), DMA_FROM_DEVICE);
		if (!cmdinfo->data_in_urb)
			return SCSI_MLQUEUE_DEVICE_BUSY;
		cmdinfo->state &= ~ALLOC_DATA_IN_URB;
	}

	if (cmdinfo->state & SUBMIT_DATA_IN_URB) {
		if (usb_submit_urb(cmdinfo->data_in_urb, gfp)) {
			scmd_printk(KERN_INFO, cmnd,
					"data in urb submission failure\n");
			return SCSI_MLQUEUE_DEVICE_BUSY;
		}
		cmdinfo->state &= ~SUBMIT_DATA_IN_URB;
	}

	if (cmdinfo->state & ALLOC_DATA_OUT_URB) {
		cmdinfo->data_out_urb = uas_alloc_data_urb(devinfo, gfp,
					devinfo->data_out_pipe, cmdinfo->stream,
					scsi_out(cmnd), DMA_TO_DEVICE);
		if (!cmdinfo->data_out_urb)
			return SCSI_MLQUEUE_DEVICE_BUSY;
		cmdinfo->state &= ~ALLOC_DATA_OUT_URB;
	}

	if (cmdinfo->state & SUBMIT_DATA_OUT_URB) {
		if (usb_submit_urb(cmdinfo->data_out_urb, gfp)) {
			scmd_printk(KERN_INFO, cmnd,
					"data out urb submission failure\n");
			return SCSI_MLQUEUE_DEVICE_BUSY;
		}
		cmdinfo->state &= ~SUBMIT_DATA_OUT_URB;
	}

	if (cmdinfo->state & ALLOC_CMD_URB) {
		cmdinfo->cmd_urb = uas_alloc_cmd_urb(devinfo, gfp, cmnd,
							cmdinfo->stream);
		if (!cmdinfo->cmd_urb)
			return SCSI_MLQUEUE_DEVICE_BUSY;
		cmdinfo->state &= ~ALLOC_CMD_URB;
	}

	if (cmdinfo->state & SUBMIT_CMD_URB) {
		if (usb_submit_urb(cmdinfo->cmd_urb, gfp)) {
			scmd_printk(KERN_INFO, cmnd,
					"cmd urb submission failure\n");
			return SCSI_MLQUEUE_DEVICE_BUSY;
		}
		cmdinfo->state &= ~SUBMIT_CMD_URB;
	}

	return 0;
}

static int uas_queuecommand_lck(struct scsi_cmnd *cmnd,
					void (*done)(struct scsi_cmnd *))
{
	struct scsi_device *sdev = cmnd->device;
	struct uas_dev_info *devinfo = sdev->hostdata;
	struct uas_cmd_info *cmdinfo = (void *)&cmnd->SCp;
	int err;

	BUILD_BUG_ON(sizeof(struct uas_cmd_info) > sizeof(struct scsi_pointer));

	if (!cmdinfo->status_urb && sdev->current_cmnd)
		return SCSI_MLQUEUE_DEVICE_BUSY;

	if (blk_rq_tagged(cmnd->request)) {
		cmdinfo->stream = cmnd->request->tag + 1;
	} else {
		sdev->current_cmnd = cmnd;
		cmdinfo->stream = 1;
	}

	cmnd->scsi_done = done;

	cmdinfo->state = ALLOC_STATUS_URB | SUBMIT_STATUS_URB |
			ALLOC_CMD_URB | SUBMIT_CMD_URB;

	switch (cmnd->sc_data_direction) {
	case DMA_FROM_DEVICE:
		cmdinfo->state |= ALLOC_DATA_IN_URB | SUBMIT_DATA_IN_URB;
		break;
	case DMA_BIDIRECTIONAL:
		cmdinfo->state |= ALLOC_DATA_IN_URB | SUBMIT_DATA_IN_URB;
	case DMA_TO_DEVICE:
		cmdinfo->state |= ALLOC_DATA_OUT_URB | SUBMIT_DATA_OUT_URB;
	case DMA_NONE:
		break;
	}

	if (!devinfo->use_streams) {
		cmdinfo->state &= ~(SUBMIT_DATA_IN_URB | SUBMIT_DATA_OUT_URB);
		cmdinfo->stream = 0;
	}

	err = uas_submit_urbs(cmnd, devinfo, GFP_ATOMIC);
	if (err) {
		/* If we did nothing, give up now */
		if (cmdinfo->state & SUBMIT_STATUS_URB) {
			usb_free_urb(cmdinfo->status_urb);
			return SCSI_MLQUEUE_DEVICE_BUSY;
		}
		spin_lock(&uas_work_lock);
		list_add_tail(&cmdinfo->list, &uas_work_list);
		spin_unlock(&uas_work_lock);
		schedule_work(&uas_work);
	}

	return 0;
}

static DEF_SCSI_QCMD(uas_queuecommand)

static int uas_eh_abort_handler(struct scsi_cmnd *cmnd)
{
	struct scsi_device *sdev = cmnd->device;
	sdev_printk(KERN_INFO, sdev, "%s tag %d\n", __func__,
							cmnd->request->tag);

/* XXX: Send ABORT TASK Task Management command */
	return FAILED;
}

static int uas_eh_device_reset_handler(struct scsi_cmnd *cmnd)
{
	struct scsi_device *sdev = cmnd->device;
	sdev_printk(KERN_INFO, sdev, "%s tag %d\n", __func__,
							cmnd->request->tag);

/* XXX: Send LOGICAL UNIT RESET Task Management command */
	return FAILED;
}

static int uas_eh_target_reset_handler(struct scsi_cmnd *cmnd)
{
	struct scsi_device *sdev = cmnd->device;
	sdev_printk(KERN_INFO, sdev, "%s tag %d\n", __func__,
							cmnd->request->tag);

/* XXX: Can we reset just the one USB interface?
 * Would calling usb_set_interface() have the right effect?
 */
	return FAILED;
}

static int uas_eh_bus_reset_handler(struct scsi_cmnd *cmnd)
{
	struct scsi_device *sdev = cmnd->device;
	struct uas_dev_info *devinfo = sdev->hostdata;
	struct usb_device *udev = devinfo->udev;

	sdev_printk(KERN_INFO, sdev, "%s tag %d\n", __func__,
							cmnd->request->tag);

	if (usb_reset_device(udev))
		return SUCCESS;

	return FAILED;
}

static int uas_slave_alloc(struct scsi_device *sdev)
{
	sdev->hostdata = (void *)sdev->host->hostdata[0];
	return 0;
}

static int uas_slave_configure(struct scsi_device *sdev)
{
	struct uas_dev_info *devinfo = sdev->hostdata;
	scsi_set_tag_type(sdev, MSG_ORDERED_TAG);
	scsi_activate_tcq(sdev, devinfo->qdepth - 1);
	return 0;
}

static struct scsi_host_template uas_host_template = {
	.module = THIS_MODULE,
	.name = "uas",
	.queuecommand = uas_queuecommand,
	.slave_alloc = uas_slave_alloc,
	.slave_configure = uas_slave_configure,
	.eh_abort_handler = uas_eh_abort_handler,
	.eh_device_reset_handler = uas_eh_device_reset_handler,
	.eh_target_reset_handler = uas_eh_target_reset_handler,
	.eh_bus_reset_handler = uas_eh_bus_reset_handler,
	.can_queue = 65536,	/* Is there a limit on the _host_ ? */
	.this_id = -1,
	.sg_tablesize = SG_NONE,
	.cmd_per_lun = 1,	/* until we override it */
	.skip_settle_delay = 1,
	.ordered_tag = 1,
};

static struct usb_device_id uas_usb_ids[] = {
	{ USB_INTERFACE_INFO(USB_CLASS_MASS_STORAGE, USB_SC_SCSI, USB_PR_BULK) },
	{ USB_INTERFACE_INFO(USB_CLASS_MASS_STORAGE, USB_SC_SCSI, USB_PR_UAS) },
	/* 0xaa is a prototype device I happen to have access to */
	{ USB_INTERFACE_INFO(USB_CLASS_MASS_STORAGE, USB_SC_SCSI, 0xaa) },
	{ }
};
MODULE_DEVICE_TABLE(usb, uas_usb_ids);

static int uas_is_interface(struct usb_host_interface *intf)
{
	return (intf->desc.bInterfaceClass == USB_CLASS_MASS_STORAGE &&
		intf->desc.bInterfaceSubClass == USB_SC_SCSI &&
		intf->desc.bInterfaceProtocol == USB_PR_UAS);
}

static int uas_switch_interface(struct usb_device *udev,
						struct usb_interface *intf)
{
	int i;

	if (uas_is_interface(intf->cur_altsetting))
		return 0;

	for (i = 0; i < intf->num_altsetting; i++) {
		struct usb_host_interface *alt = &intf->altsetting[i];
		if (alt == intf->cur_altsetting)
			continue;
		if (uas_is_interface(alt))
			return usb_set_interface(udev,
						alt->desc.bInterfaceNumber,
						alt->desc.bAlternateSetting);
	}

	return -ENODEV;
}

static void uas_configure_endpoints(struct uas_dev_info *devinfo)
{
	struct usb_host_endpoint *eps[4] = { };
	struct usb_interface *intf = devinfo->intf;
	struct usb_device *udev = devinfo->udev;
	struct usb_host_endpoint *endpoint = intf->cur_altsetting->endpoint;
	unsigned i, n_endpoints = intf->cur_altsetting->desc.bNumEndpoints;

	devinfo->uas_sense_old = 0;

	for (i = 0; i < n_endpoints; i++) {
		unsigned char *extra = endpoint[i].extra;
		int len = endpoint[i].extralen;
		while (len > 1) {
			if (extra[1] == USB_DT_PIPE_USAGE) {
				unsigned pipe_id = extra[2];
				if (pipe_id > 0 && pipe_id < 5)
					eps[pipe_id - 1] = &endpoint[i];
				break;
			}
			len -= extra[0];
			extra += extra[0];
		}
	}

	/*
	 * Assume that if we didn't find a control pipe descriptor, we're
	 * using a device with old firmware that happens to be set up like
	 * this.
	 */
	if (!eps[0]) {
		devinfo->cmd_pipe = usb_sndbulkpipe(udev, 1);
		devinfo->status_pipe = usb_rcvbulkpipe(udev, 1);
		devinfo->data_in_pipe = usb_rcvbulkpipe(udev, 2);
		devinfo->data_out_pipe = usb_sndbulkpipe(udev, 2);

		eps[1] = usb_pipe_endpoint(udev, devinfo->status_pipe);
		eps[2] = usb_pipe_endpoint(udev, devinfo->data_in_pipe);
		eps[3] = usb_pipe_endpoint(udev, devinfo->data_out_pipe);
	} else {
		devinfo->cmd_pipe = usb_sndbulkpipe(udev,
						eps[0]->desc.bEndpointAddress);
		devinfo->status_pipe = usb_rcvbulkpipe(udev,
						eps[1]->desc.bEndpointAddress);
		devinfo->data_in_pipe = usb_rcvbulkpipe(udev,
						eps[2]->desc.bEndpointAddress);
		devinfo->data_out_pipe = usb_sndbulkpipe(udev,
						eps[3]->desc.bEndpointAddress);
	}

	devinfo->qdepth = usb_alloc_streams(devinfo->intf, eps + 1, 3, 256,
								GFP_KERNEL);
	if (devinfo->qdepth < 0) {
		devinfo->qdepth = 256;
		devinfo->use_streams = 0;
	} else {
		devinfo->use_streams = 1;
	}
}

/*
 * XXX: What I'd like to do here is register a SCSI host for each USB host in
 * the system.  Follow usb-storage's design of registering a SCSI host for
 * each USB device for the moment.  Can implement this by walking up the
 * USB hierarchy until we find a USB host.
 */
static int uas_probe(struct usb_interface *intf, const struct usb_device_id *id)
{
	int result;
	struct Scsi_Host *shost;
	struct uas_dev_info *devinfo;
	struct usb_device *udev = interface_to_usbdev(intf);

	if (uas_switch_interface(udev, intf))
		return -ENODEV;

	devinfo = kmalloc(sizeof(struct uas_dev_info), GFP_KERNEL);
	if (!devinfo)
		return -ENOMEM;

	result = -ENOMEM;
	shost = scsi_host_alloc(&uas_host_template, sizeof(void *));
	if (!shost)
		goto free;

	shost->max_cmd_len = 16 + 252;
	shost->max_id = 1;
	shost->sg_tablesize = udev->bus->sg_tablesize;

	result = scsi_add_host(shost, &intf->dev);
	if (result)
		goto free;
	shost->hostdata[0] = (unsigned long)devinfo;

	devinfo->intf = intf;
	devinfo->udev = udev;
	uas_configure_endpoints(devinfo);

	scsi_scan_host(shost);
	usb_set_intfdata(intf, shost);
	return result;
 free:
	kfree(devinfo);
	if (shost)
		scsi_host_put(shost);
	return result;
}

static int uas_pre_reset(struct usb_interface *intf)
{
/* XXX: Need to return 1 if it's not our device in error handling */
	return 0;
}

static int uas_post_reset(struct usb_interface *intf)
{
/* XXX: Need to return 1 if it's not our device in error handling */
	return 0;
}

static void uas_disconnect(struct usb_interface *intf)
{
	struct usb_device *udev = interface_to_usbdev(intf);
	struct usb_host_endpoint *eps[3];
	struct Scsi_Host *shost = usb_get_intfdata(intf);
	struct uas_dev_info *devinfo = (void *)shost->hostdata[0];

	scsi_remove_host(shost);

	eps[0] = usb_pipe_endpoint(udev, devinfo->status_pipe);
	eps[1] = usb_pipe_endpoint(udev, devinfo->data_in_pipe);
	eps[2] = usb_pipe_endpoint(udev, devinfo->data_out_pipe);
	usb_free_streams(intf, eps, 3, GFP_KERNEL);

	kfree(devinfo);
}

/*
 * XXX: Should this plug into libusual so we can auto-upgrade devices from
 * Bulk-Only to UAS?
 */
static struct usb_driver uas_driver = {
	.name = "uas",
	.probe = uas_probe,
	.disconnect = uas_disconnect,
	.pre_reset = uas_pre_reset,
	.post_reset = uas_post_reset,
	.id_table = uas_usb_ids,
};

module_usb_driver(uas_driver);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Matthew Wilcox and Sarah Sharp");