summaryrefslogtreecommitdiff
path: root/drivers/usb/gadget/storage_common.c
blob: dbce3a9074e6ebac353ec891ecc7c6726c5359b7 (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
/*
 * storage_common.c -- Common definitions for mass storage functionality
 *
 * Copyright (C) 2003-2008 Alan Stern
 * Copyeight (C) 2009 Samsung Electronics
 * Author: Michal Nazarewicz (mina86@mina86.com)
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 */

/*
 * This file requires the following identifiers used in USB strings to
 * be defined (each of type pointer to char):
 *  - fsg_string_interface    -- name of the interface
 */

/*
 * When USB_GADGET_DEBUG_FILES is defined the module param num_buffers
 * sets the number of pipeline buffers (length of the fsg_buffhd array).
 * The valid range of num_buffers is: num >= 2 && num <= 4.
 */


#include <linux/usb/storage.h>
#include <scsi/scsi.h>
#include <asm/unaligned.h>


/*
 * Thanks to NetChip Technologies for donating this product ID.
 *
 * DO NOT REUSE THESE IDs with any other driver!!  Ever!!
 * Instead:  allocate your own, using normal USB-IF procedures.
 */
#define FSG_VENDOR_ID	0x0525	/* NetChip */
#define FSG_PRODUCT_ID	0xa4a5	/* Linux-USB File-backed Storage Gadget */


/*-------------------------------------------------------------------------*/


#ifndef DEBUG
#undef VERBOSE_DEBUG
#undef DUMP_MSGS
#endif /* !DEBUG */

#ifdef VERBOSE_DEBUG
#define VLDBG	LDBG
#else
#define VLDBG(lun, fmt, args...) do { } while (0)
#endif /* VERBOSE_DEBUG */

#define LDBG(lun, fmt, args...)   dev_dbg (&(lun)->dev, fmt, ## args)
#define LERROR(lun, fmt, args...) dev_err (&(lun)->dev, fmt, ## args)
#define LWARN(lun, fmt, args...)  dev_warn(&(lun)->dev, fmt, ## args)
#define LINFO(lun, fmt, args...)  dev_info(&(lun)->dev, fmt, ## args)


#ifdef DUMP_MSGS

#  define dump_msg(fsg, /* const char * */ label,			\
		   /* const u8 * */ buf, /* unsigned */ length) do {	\
	if (length < 512) {						\
		DBG(fsg, "%s, length %u:\n", label, length);		\
		print_hex_dump(KERN_DEBUG, "", DUMP_PREFIX_OFFSET,	\
			       16, 1, buf, length, 0);			\
	}								\
} while (0)

#  define dump_cdb(fsg) do { } while (0)

#else

#  define dump_msg(fsg, /* const char * */ label, \
		   /* const u8 * */ buf, /* unsigned */ length) do { } while (0)

#  ifdef VERBOSE_DEBUG

#    define dump_cdb(fsg)						\
	print_hex_dump(KERN_DEBUG, "SCSI CDB: ", DUMP_PREFIX_NONE,	\
		       16, 1, (fsg)->cmnd, (fsg)->cmnd_size, 0)		\

#  else

#    define dump_cdb(fsg) do { } while (0)

#  endif /* VERBOSE_DEBUG */

#endif /* DUMP_MSGS */

/*-------------------------------------------------------------------------*/

/* Length of a SCSI Command Data Block */
#define MAX_COMMAND_SIZE	16

/* SCSI Sense Key/Additional Sense Code/ASC Qualifier values */
#define SS_NO_SENSE				0
#define SS_COMMUNICATION_FAILURE		0x040800
#define SS_INVALID_COMMAND			0x052000
#define SS_INVALID_FIELD_IN_CDB			0x052400
#define SS_LOGICAL_BLOCK_ADDRESS_OUT_OF_RANGE	0x052100
#define SS_LOGICAL_UNIT_NOT_SUPPORTED		0x052500
#define SS_MEDIUM_NOT_PRESENT			0x023a00
#define SS_MEDIUM_REMOVAL_PREVENTED		0x055302
#define SS_NOT_READY_TO_READY_TRANSITION	0x062800
#define SS_RESET_OCCURRED			0x062900
#define SS_SAVING_PARAMETERS_NOT_SUPPORTED	0x053900
#define SS_UNRECOVERED_READ_ERROR		0x031100
#define SS_WRITE_ERROR				0x030c02
#define SS_WRITE_PROTECTED			0x072700

#define SK(x)		((u8) ((x) >> 16))	/* Sense Key byte, etc. */
#define ASC(x)		((u8) ((x) >> 8))
#define ASCQ(x)		((u8) (x))


/*-------------------------------------------------------------------------*/


struct fsg_lun {
	struct file	*filp;
	loff_t		file_length;
	loff_t		num_sectors;

	unsigned int	initially_ro:1;
	unsigned int	ro:1;
	unsigned int	removable:1;
	unsigned int	cdrom:1;
	unsigned int	prevent_medium_removal:1;
	unsigned int	registered:1;
	unsigned int	info_valid:1;
	unsigned int	nofua:1;

	u32		sense_data;
	u32		sense_data_info;
	u32		unit_attention_data;

	unsigned int	blkbits;	/* Bits of logical block size of bound block device */
	unsigned int	blksize;	/* logical block size of bound block device */
	struct device	dev;
};

static inline bool fsg_lun_is_open(struct fsg_lun *curlun)
{
	return curlun->filp != NULL;
}

static inline struct fsg_lun *fsg_lun_from_dev(struct device *dev)
{
	return container_of(dev, struct fsg_lun, dev);
}


/* Big enough to hold our biggest descriptor */
#define EP0_BUFSIZE	256
#define DELAYED_STATUS	(EP0_BUFSIZE + 999)	/* An impossibly large value */

#ifdef CONFIG_USB_GADGET_DEBUG_FILES

static unsigned int fsg_num_buffers = CONFIG_USB_GADGET_STORAGE_NUM_BUFFERS;
module_param_named(num_buffers, fsg_num_buffers, uint, S_IRUGO);
MODULE_PARM_DESC(num_buffers, "Number of pipeline buffers");

#else

/*
 * Number of buffers we will use.
 * 2 is usually enough for good buffering pipeline
 */
#define fsg_num_buffers	CONFIG_USB_GADGET_STORAGE_NUM_BUFFERS

#endif /* CONFIG_USB_DEBUG */

/* check if fsg_num_buffers is within a valid range */
static inline int fsg_num_buffers_validate(void)
{
	if (fsg_num_buffers >= 2 && fsg_num_buffers <= 4)
		return 0;
	pr_err("fsg_num_buffers %u is out of range (%d to %d)\n",
	       fsg_num_buffers, 2 ,4);
	return -EINVAL;
}

/* Default size of buffer length. */
#define FSG_BUFLEN	((u32)16384)

/* Maximal number of LUNs supported in mass storage function */
#define FSG_MAX_LUNS	8

enum fsg_buffer_state {
	BUF_STATE_EMPTY = 0,
	BUF_STATE_FULL,
	BUF_STATE_BUSY
};

struct fsg_buffhd {
	void				*buf;
	enum fsg_buffer_state		state;
	struct fsg_buffhd		*next;

	/*
	 * The NetChip 2280 is faster, and handles some protocol faults
	 * better, if we don't submit any short bulk-out read requests.
	 * So we will record the intended request length here.
	 */
	unsigned int			bulk_out_intended_length;

	struct usb_request		*inreq;
	int				inreq_busy;
	struct usb_request		*outreq;
	int				outreq_busy;
};

enum fsg_state {
	/* This one isn't used anywhere */
	FSG_STATE_COMMAND_PHASE = -10,
	FSG_STATE_DATA_PHASE,
	FSG_STATE_STATUS_PHASE,

	FSG_STATE_IDLE = 0,
	FSG_STATE_ABORT_BULK_OUT,
	FSG_STATE_RESET,
	FSG_STATE_INTERFACE_CHANGE,
	FSG_STATE_CONFIG_CHANGE,
	FSG_STATE_DISCONNECT,
	FSG_STATE_EXIT,
	FSG_STATE_TERMINATED
};

enum data_direction {
	DATA_DIR_UNKNOWN = 0,
	DATA_DIR_FROM_HOST,
	DATA_DIR_TO_HOST,
	DATA_DIR_NONE
};


/*-------------------------------------------------------------------------*/


static inline u32 get_unaligned_be24(u8 *buf)
{
	return 0xffffff & (u32) get_unaligned_be32(buf - 1);
}


/*-------------------------------------------------------------------------*/


enum {
	FSG_STRING_INTERFACE
};


/* There is only one interface. */

static struct usb_interface_descriptor
fsg_intf_desc = {
	.bLength =		sizeof fsg_intf_desc,
	.bDescriptorType =	USB_DT_INTERFACE,

	.bNumEndpoints =	2,		/* Adjusted during fsg_bind() */
	.bInterfaceClass =	USB_CLASS_MASS_STORAGE,
	.bInterfaceSubClass =	USB_SC_SCSI,	/* Adjusted during fsg_bind() */
	.bInterfaceProtocol =	USB_PR_BULK,	/* Adjusted during fsg_bind() */
	.iInterface =		FSG_STRING_INTERFACE,
};

/*
 * Three full-speed endpoint descriptors: bulk-in, bulk-out, and
 * interrupt-in.
 */

static struct usb_endpoint_descriptor
fsg_fs_bulk_in_desc = {
	.bLength =		USB_DT_ENDPOINT_SIZE,
	.bDescriptorType =	USB_DT_ENDPOINT,

	.bEndpointAddress =	USB_DIR_IN,
	.bmAttributes =		USB_ENDPOINT_XFER_BULK,
	/* wMaxPacketSize set by autoconfiguration */
};

static struct usb_endpoint_descriptor
fsg_fs_bulk_out_desc = {
	.bLength =		USB_DT_ENDPOINT_SIZE,
	.bDescriptorType =	USB_DT_ENDPOINT,

	.bEndpointAddress =	USB_DIR_OUT,
	.bmAttributes =		USB_ENDPOINT_XFER_BULK,
	/* wMaxPacketSize set by autoconfiguration */
};

static struct usb_descriptor_header *fsg_fs_function[] = {
	(struct usb_descriptor_header *) &fsg_intf_desc,
	(struct usb_descriptor_header *) &fsg_fs_bulk_in_desc,
	(struct usb_descriptor_header *) &fsg_fs_bulk_out_desc,
	NULL,
};


/*
 * USB 2.0 devices need to expose both high speed and full speed
 * descriptors, unless they only run at full speed.
 *
 * That means alternate endpoint descriptors (bigger packets)
 * and a "device qualifier" ... plus more construction options
 * for the configuration descriptor.
 */
static struct usb_endpoint_descriptor
fsg_hs_bulk_in_desc = {
	.bLength =		USB_DT_ENDPOINT_SIZE,
	.bDescriptorType =	USB_DT_ENDPOINT,

	/* bEndpointAddress copied from fs_bulk_in_desc during fsg_bind() */
	.bmAttributes =		USB_ENDPOINT_XFER_BULK,
	.wMaxPacketSize =	cpu_to_le16(512),
};

static struct usb_endpoint_descriptor
fsg_hs_bulk_out_desc = {
	.bLength =		USB_DT_ENDPOINT_SIZE,
	.bDescriptorType =	USB_DT_ENDPOINT,

	/* bEndpointAddress copied from fs_bulk_out_desc during fsg_bind() */
	.bmAttributes =		USB_ENDPOINT_XFER_BULK,
	.wMaxPacketSize =	cpu_to_le16(512),
	.bInterval =		1,	/* NAK every 1 uframe */
};


static struct usb_descriptor_header *fsg_hs_function[] = {
	(struct usb_descriptor_header *) &fsg_intf_desc,
	(struct usb_descriptor_header *) &fsg_hs_bulk_in_desc,
	(struct usb_descriptor_header *) &fsg_hs_bulk_out_desc,
	NULL,
};

static struct usb_endpoint_descriptor
fsg_ss_bulk_in_desc = {
	.bLength =		USB_DT_ENDPOINT_SIZE,
	.bDescriptorType =	USB_DT_ENDPOINT,

	/* bEndpointAddress copied from fs_bulk_in_desc during fsg_bind() */
	.bmAttributes =		USB_ENDPOINT_XFER_BULK,
	.wMaxPacketSize =	cpu_to_le16(1024),
};

static struct usb_ss_ep_comp_descriptor fsg_ss_bulk_in_comp_desc = {
	.bLength =		sizeof(fsg_ss_bulk_in_comp_desc),
	.bDescriptorType =	USB_DT_SS_ENDPOINT_COMP,

	/*.bMaxBurst =		DYNAMIC, */
};

static struct usb_endpoint_descriptor
fsg_ss_bulk_out_desc = {
	.bLength =		USB_DT_ENDPOINT_SIZE,
	.bDescriptorType =	USB_DT_ENDPOINT,

	/* bEndpointAddress copied from fs_bulk_out_desc during fsg_bind() */
	.bmAttributes =		USB_ENDPOINT_XFER_BULK,
	.wMaxPacketSize =	cpu_to_le16(1024),
};

static struct usb_ss_ep_comp_descriptor fsg_ss_bulk_out_comp_desc = {
	.bLength =		sizeof(fsg_ss_bulk_in_comp_desc),
	.bDescriptorType =	USB_DT_SS_ENDPOINT_COMP,

	/*.bMaxBurst =		DYNAMIC, */
};

static struct usb_descriptor_header *fsg_ss_function[] = {
	(struct usb_descriptor_header *) &fsg_intf_desc,
	(struct usb_descriptor_header *) &fsg_ss_bulk_in_desc,
	(struct usb_descriptor_header *) &fsg_ss_bulk_in_comp_desc,
	(struct usb_descriptor_header *) &fsg_ss_bulk_out_desc,
	(struct usb_descriptor_header *) &fsg_ss_bulk_out_comp_desc,
	NULL,
};

/* Static strings, in UTF-8 (for simplicity we use only ASCII characters) */
static struct usb_string		fsg_strings[] = {
	{FSG_STRING_INTERFACE,		fsg_string_interface},
	{}
};

static struct usb_gadget_strings	fsg_stringtab = {
	.language	= 0x0409,		/* en-us */
	.strings	= fsg_strings,
};


 /*-------------------------------------------------------------------------*/

/*
 * If the next two routines are called while the gadget is registered,
 * the caller must own fsg->filesem for writing.
 */

static void fsg_lun_close(struct fsg_lun *curlun)
{
	if (curlun->filp) {
		LDBG(curlun, "close backing file\n");
		fput(curlun->filp);
		curlun->filp = NULL;
	}
}


static int fsg_lun_open(struct fsg_lun *curlun, const char *filename)
{
	int				ro;
	struct file			*filp = NULL;
	int				rc = -EINVAL;
	struct inode			*inode = NULL;
	loff_t				size;
	loff_t				num_sectors;
	loff_t				min_sectors;
	unsigned int			blkbits;
	unsigned int			blksize;

	/* R/W if we can, R/O if we must */
	ro = curlun->initially_ro;
	if (!ro) {
		filp = filp_open(filename, O_RDWR | O_LARGEFILE, 0);
		if (PTR_ERR(filp) == -EROFS || PTR_ERR(filp) == -EACCES)
			ro = 1;
	}
	if (ro)
		filp = filp_open(filename, O_RDONLY | O_LARGEFILE, 0);
	if (IS_ERR(filp)) {
		LINFO(curlun, "unable to open backing file: %s\n", filename);
		return PTR_ERR(filp);
	}

	if (!(filp->f_mode & FMODE_WRITE))
		ro = 1;

	inode = file_inode(filp);
	if ((!S_ISREG(inode->i_mode) && !S_ISBLK(inode->i_mode))) {
		LINFO(curlun, "invalid file type: %s\n", filename);
		goto out;
	}

	/*
	 * If we can't read the file, it's no good.
	 * If we can't write the file, use it read-only.
	 */
	if (!(filp->f_op->read || filp->f_op->aio_read)) {
		LINFO(curlun, "file not readable: %s\n", filename);
		goto out;
	}
	if (!(filp->f_op->write || filp->f_op->aio_write))
		ro = 1;

	size = i_size_read(inode->i_mapping->host);
	if (size < 0) {
		LINFO(curlun, "unable to find file size: %s\n", filename);
		rc = (int) size;
		goto out;
	}

	if (curlun->cdrom) {
		blksize = 2048;
		blkbits = 11;
	} else if (inode->i_bdev) {
		blksize = bdev_logical_block_size(inode->i_bdev);
		blkbits = blksize_bits(blksize);
	} else {
		blksize = 512;
		blkbits = 9;
	}

	num_sectors = size >> blkbits; /* File size in logic-block-size blocks */
	min_sectors = 1;
	if (curlun->cdrom) {
		min_sectors = 300;	/* Smallest track is 300 frames */
		if (num_sectors >= 256*60*75) {
			num_sectors = 256*60*75 - 1;
			LINFO(curlun, "file too big: %s\n", filename);
			LINFO(curlun, "using only first %d blocks\n",
					(int) num_sectors);
		}
	}
	if (num_sectors < min_sectors) {
		LINFO(curlun, "file too small: %s\n", filename);
		rc = -ETOOSMALL;
		goto out;
	}

	if (fsg_lun_is_open(curlun))
		fsg_lun_close(curlun);

	curlun->blksize = blksize;
	curlun->blkbits = blkbits;
	curlun->ro = ro;
	curlun->filp = filp;
	curlun->file_length = size;
	curlun->num_sectors = num_sectors;
	LDBG(curlun, "open backing file: %s\n", filename);
	return 0;

out:
	fput(filp);
	return rc;
}


/*-------------------------------------------------------------------------*/

/*
 * Sync the file data, don't bother with the metadata.
 * This code was copied from fs/buffer.c:sys_fdatasync().
 */
static int fsg_lun_fsync_sub(struct fsg_lun *curlun)
{
	struct file	*filp = curlun->filp;

	if (curlun->ro || !filp)
		return 0;
	return vfs_fsync(filp, 1);
}

static void store_cdrom_address(u8 *dest, int msf, u32 addr)
{
	if (msf) {
		/* Convert to Minutes-Seconds-Frames */
		addr >>= 2;		/* Convert to 2048-byte frames */
		addr += 2*75;		/* Lead-in occupies 2 seconds */
		dest[3] = addr % 75;	/* Frames */
		addr /= 75;
		dest[2] = addr % 60;	/* Seconds */
		addr /= 60;
		dest[1] = addr;		/* Minutes */
		dest[0] = 0;		/* Reserved */
	} else {
		/* Absolute sector */
		put_unaligned_be32(addr, dest);
	}
}


/*-------------------------------------------------------------------------*/


static ssize_t fsg_show_ro(struct device *dev, struct device_attribute *attr,
			   char *buf)
{
	struct fsg_lun	*curlun = fsg_lun_from_dev(dev);

	return sprintf(buf, "%d\n", fsg_lun_is_open(curlun)
				  ? curlun->ro
				  : curlun->initially_ro);
}

static ssize_t fsg_show_nofua(struct device *dev, struct device_attribute *attr,
			      char *buf)
{
	struct fsg_lun	*curlun = fsg_lun_from_dev(dev);

	return sprintf(buf, "%u\n", curlun->nofua);
}

static ssize_t fsg_show_file(struct device *dev, struct device_attribute *attr,
			     char *buf)
{
	struct fsg_lun	*curlun = fsg_lun_from_dev(dev);
	struct rw_semaphore	*filesem = dev_get_drvdata(dev);
	char		*p;
	ssize_t		rc;

	down_read(filesem);
	if (fsg_lun_is_open(curlun)) {	/* Get the complete pathname */
		p = d_path(&curlun->filp->f_path, buf, PAGE_SIZE - 1);
		if (IS_ERR(p))
			rc = PTR_ERR(p);
		else {
			rc = strlen(p);
			memmove(buf, p, rc);
			buf[rc] = '\n';		/* Add a newline */
			buf[++rc] = 0;
		}
	} else {				/* No file, return 0 bytes */
		*buf = 0;
		rc = 0;
	}
	up_read(filesem);
	return rc;
}


static ssize_t fsg_store_ro(struct device *dev, struct device_attribute *attr,
			    const char *buf, size_t count)
{
	ssize_t		rc;
	struct fsg_lun	*curlun = fsg_lun_from_dev(dev);
	struct rw_semaphore	*filesem = dev_get_drvdata(dev);
	unsigned	ro;

	rc = kstrtouint(buf, 2, &ro);
	if (rc)
		return rc;

	/*
	 * Allow the write-enable status to change only while the
	 * backing file is closed.
	 */
	down_read(filesem);
	if (fsg_lun_is_open(curlun)) {
		LDBG(curlun, "read-only status change prevented\n");
		rc = -EBUSY;
	} else {
		curlun->ro = ro;
		curlun->initially_ro = ro;
		LDBG(curlun, "read-only status set to %d\n", curlun->ro);
		rc = count;
	}
	up_read(filesem);
	return rc;
}

static ssize_t fsg_store_nofua(struct device *dev,
			       struct device_attribute *attr,
			       const char *buf, size_t count)
{
	struct fsg_lun	*curlun = fsg_lun_from_dev(dev);
	unsigned	nofua;
	int		ret;

	ret = kstrtouint(buf, 2, &nofua);
	if (ret)
		return ret;

	/* Sync data when switching from async mode to sync */
	if (!nofua && curlun->nofua)
		fsg_lun_fsync_sub(curlun);

	curlun->nofua = nofua;

	return count;
}

static ssize_t fsg_store_file(struct device *dev, struct device_attribute *attr,
			      const char *buf, size_t count)
{
	struct fsg_lun	*curlun = fsg_lun_from_dev(dev);
	struct rw_semaphore	*filesem = dev_get_drvdata(dev);
	int		rc = 0;

	if (curlun->prevent_medium_removal && fsg_lun_is_open(curlun)) {
		LDBG(curlun, "eject attempt prevented\n");
		return -EBUSY;				/* "Door is locked" */
	}

	/* Remove a trailing newline */
	if (count > 0 && buf[count-1] == '\n')
		((char *) buf)[count-1] = 0;		/* Ugh! */

	/* Load new medium */
	down_write(filesem);
	if (count > 0 && buf[0]) {
		/* fsg_lun_open() will close existing file if any. */
		rc = fsg_lun_open(curlun, buf);
		if (rc == 0)
			curlun->unit_attention_data =
					SS_NOT_READY_TO_READY_TRANSITION;
	} else if (fsg_lun_is_open(curlun)) {
		fsg_lun_close(curlun);
		curlun->unit_attention_data = SS_MEDIUM_NOT_PRESENT;
	}
	up_write(filesem);
	return (rc < 0 ? rc : count);
}