xref: /linux/drivers/usb/core/devices.c (revision f3d9478b2ce468c3115b02ecae7e975990697f15)
1 /*
2  * devices.c
3  * (C) Copyright 1999 Randy Dunlap.
4  * (C) Copyright 1999,2000 Thomas Sailer <sailer@ife.ee.ethz.ch>. (proc file per device)
5  * (C) Copyright 1999 Deti Fliegl (new USB architecture)
6  *
7  * This program is free software; you can redistribute it and/or modify
8  * it under the terms of the GNU General Public License as published by
9  * the Free Software Foundation; either version 2 of the License, or
10  * (at your option) any later version.
11  *
12  * This program is distributed in the hope that it will be useful,
13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
15  * GNU General Public License for more details.
16  *
17  * You should have received a copy of the GNU General Public License
18  * along with this program; if not, write to the Free Software
19  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
20  *
21  *************************************************************
22  *
23  * <mountpoint>/devices contains USB topology, device, config, class,
24  * interface, & endpoint data.
25  *
26  * I considered using /proc/bus/usb/devices/device# for each device
27  * as it is attached or detached, but I didn't like this for some
28  * reason -- maybe it's just too deep of a directory structure.
29  * I also don't like looking in multiple places to gather and view
30  * the data.  Having only one file for ./devices also prevents race
31  * conditions that could arise if a program was reading device info
32  * for devices that are being removed (unplugged).  (That is, the
33  * program may find a directory for devnum_12 then try to open it,
34  * but it was just unplugged, so the directory is now deleted.
35  * But programs would just have to be prepared for situations like
36  * this in any plug-and-play environment.)
37  *
38  * 1999-12-16: Thomas Sailer <sailer@ife.ee.ethz.ch>
39  *   Converted the whole proc stuff to real
40  *   read methods. Now not the whole device list needs to fit
41  *   into one page, only the device list for one bus.
42  *   Added a poll method to /proc/bus/usb/devices, to wake
43  *   up an eventual usbd
44  * 2000-01-04: Thomas Sailer <sailer@ife.ee.ethz.ch>
45  *   Turned into its own filesystem
46  * 2000-07-05: Ashley Montanaro <ashley@compsoc.man.ac.uk>
47  *   Converted file reading routine to dump to buffer once
48  *   per device, not per bus
49  *
50  * $Id: devices.c,v 1.5 2000/01/11 13:58:21 tom Exp $
51  */
52 
53 #include <linux/fs.h>
54 #include <linux/mm.h>
55 #include <linux/slab.h>
56 #include <linux/poll.h>
57 #include <linux/usb.h>
58 #include <linux/smp_lock.h>
59 #include <linux/usbdevice_fs.h>
60 #include <linux/mutex.h>
61 #include <asm/uaccess.h>
62 
63 #include "usb.h"
64 #include "hcd.h"
65 
66 #define MAX_TOPO_LEVEL		6
67 
68 /* Define ALLOW_SERIAL_NUMBER if you want to see the serial number of devices */
69 #define ALLOW_SERIAL_NUMBER
70 
71 static const char *format_topo =
72 /* T:  Bus=dd Lev=dd Prnt=dd Port=dd Cnt=dd Dev#=ddd Spd=ddd MxCh=dd */
73 "\nT:  Bus=%2.2d Lev=%2.2d Prnt=%2.2d Port=%2.2d Cnt=%2.2d Dev#=%3d Spd=%3s MxCh=%2d\n";
74 
75 static const char *format_string_manufacturer =
76 /* S:  Manufacturer=xxxx */
77   "S:  Manufacturer=%.100s\n";
78 
79 static const char *format_string_product =
80 /* S:  Product=xxxx */
81   "S:  Product=%.100s\n";
82 
83 #ifdef ALLOW_SERIAL_NUMBER
84 static const char *format_string_serialnumber =
85 /* S:  SerialNumber=xxxx */
86   "S:  SerialNumber=%.100s\n";
87 #endif
88 
89 static const char *format_bandwidth =
90 /* B:  Alloc=ddd/ddd us (xx%), #Int=ddd, #Iso=ddd */
91   "B:  Alloc=%3d/%3d us (%2d%%), #Int=%3d, #Iso=%3d\n";
92 
93 static const char *format_device1 =
94 /* D:  Ver=xx.xx Cls=xx(sssss) Sub=xx Prot=xx MxPS=dd #Cfgs=dd */
95   "D:  Ver=%2x.%02x Cls=%02x(%-5s) Sub=%02x Prot=%02x MxPS=%2d #Cfgs=%3d\n";
96 
97 static const char *format_device2 =
98 /* P:  Vendor=xxxx ProdID=xxxx Rev=xx.xx */
99   "P:  Vendor=%04x ProdID=%04x Rev=%2x.%02x\n";
100 
101 static const char *format_config =
102 /* C:  #Ifs=dd Cfg#=dd Atr=xx MPwr=dddmA */
103   "C:%c #Ifs=%2d Cfg#=%2d Atr=%02x MxPwr=%3dmA\n";
104 
105 static const char *format_iface =
106 /* I:  If#=dd Alt=dd #EPs=dd Cls=xx(sssss) Sub=xx Prot=xx Driver=xxxx*/
107   "I:  If#=%2d Alt=%2d #EPs=%2d Cls=%02x(%-5s) Sub=%02x Prot=%02x Driver=%s\n";
108 
109 static const char *format_endpt =
110 /* E:  Ad=xx(s) Atr=xx(ssss) MxPS=dddd Ivl=D?s */
111   "E:  Ad=%02x(%c) Atr=%02x(%-4s) MxPS=%4d Ivl=%d%cs\n";
112 
113 
114 /*
115  * Need access to the driver and USB bus lists.
116  * extern struct list_head usb_bus_list;
117  * However, these will come from functions that return ptrs to each of them.
118  */
119 
120 static DECLARE_WAIT_QUEUE_HEAD(deviceconndiscwq);
121 static unsigned int conndiscevcnt = 0;
122 
123 /* this struct stores the poll state for <mountpoint>/devices pollers */
124 struct usb_device_status {
125 	unsigned int lastev;
126 };
127 
128 struct class_info {
129 	int class;
130 	char *class_name;
131 };
132 
133 static const struct class_info clas_info[] =
134 {					/* max. 5 chars. per name string */
135 	{USB_CLASS_PER_INTERFACE,	">ifc"},
136 	{USB_CLASS_AUDIO,		"audio"},
137 	{USB_CLASS_COMM,		"comm."},
138 	{USB_CLASS_HID,			"HID"},
139 	{USB_CLASS_HUB,			"hub"},
140 	{USB_CLASS_PHYSICAL,		"PID"},
141 	{USB_CLASS_PRINTER,		"print"},
142 	{USB_CLASS_MASS_STORAGE,	"stor."},
143 	{USB_CLASS_CDC_DATA,		"data"},
144 	{USB_CLASS_APP_SPEC,		"app."},
145 	{USB_CLASS_VENDOR_SPEC,		"vend."},
146 	{USB_CLASS_STILL_IMAGE,		"still"},
147 	{USB_CLASS_CSCID,		"scard"},
148 	{USB_CLASS_CONTENT_SEC,		"c-sec"},
149 	{-1,				"unk."}		/* leave as last */
150 };
151 
152 /*****************************************************************/
153 
154 void usbfs_conn_disc_event(void)
155 {
156 	conndiscevcnt++;
157 	wake_up(&deviceconndiscwq);
158 }
159 
160 static const char *class_decode(const int class)
161 {
162 	int ix;
163 
164 	for (ix = 0; clas_info[ix].class != -1; ix++)
165 		if (clas_info[ix].class == class)
166 			break;
167 	return (clas_info[ix].class_name);
168 }
169 
170 static char *usb_dump_endpoint_descriptor (
171 	int speed,
172 	char *start,
173 	char *end,
174 	const struct usb_endpoint_descriptor *desc
175 )
176 {
177 	char dir, unit, *type;
178 	unsigned interval, in, bandwidth = 1;
179 
180 	if (start > end)
181 		return start;
182 	in = (desc->bEndpointAddress & USB_DIR_IN);
183 	dir = in ? 'I' : 'O';
184 	if (speed == USB_SPEED_HIGH) {
185 		switch (le16_to_cpu(desc->wMaxPacketSize) & (0x03 << 11)) {
186 		case 1 << 11:	bandwidth = 2; break;
187 		case 2 << 11:	bandwidth = 3; break;
188 		}
189 	}
190 
191 	/* this isn't checking for illegal values */
192 	switch (desc->bmAttributes & USB_ENDPOINT_XFERTYPE_MASK) {
193 	case USB_ENDPOINT_XFER_CONTROL:
194 		type = "Ctrl";
195 		if (speed == USB_SPEED_HIGH) 	/* uframes per NAK */
196 			interval = desc->bInterval;
197 		else
198 			interval = 0;
199 		dir = 'B';			/* ctrl is bidirectional */
200 		break;
201 	case USB_ENDPOINT_XFER_ISOC:
202 		type = "Isoc";
203 		interval = 1 << (desc->bInterval - 1);
204 		break;
205 	case USB_ENDPOINT_XFER_BULK:
206 		type = "Bulk";
207 		if (speed == USB_SPEED_HIGH && !in)	/* uframes per NAK */
208 			interval = desc->bInterval;
209 		else
210 			interval = 0;
211 		break;
212 	case USB_ENDPOINT_XFER_INT:
213 		type = "Int.";
214 		if (speed == USB_SPEED_HIGH) {
215 			interval = 1 << (desc->bInterval - 1);
216 		} else
217 			interval = desc->bInterval;
218 		break;
219 	default:	/* "can't happen" */
220 		return start;
221 	}
222 	interval *= (speed == USB_SPEED_HIGH) ? 125 : 1000;
223 	if (interval % 1000)
224 		unit = 'u';
225 	else {
226 		unit = 'm';
227 		interval /= 1000;
228 	}
229 
230 	start += sprintf(start, format_endpt, desc->bEndpointAddress, dir,
231 			 desc->bmAttributes, type,
232 			 (le16_to_cpu(desc->wMaxPacketSize) & 0x07ff) * bandwidth,
233 			 interval, unit);
234 	return start;
235 }
236 
237 static char *usb_dump_interface_descriptor(char *start, char *end,
238 	const struct usb_interface_cache *intfc,
239 	const struct usb_interface *iface,
240 	int setno)
241 {
242 	const struct usb_interface_descriptor *desc = &intfc->altsetting[setno].desc;
243 	const char *driver_name = "";
244 
245 	if (start > end)
246 		return start;
247 	down_read(&usb_bus_type.subsys.rwsem);
248 	if (iface)
249 		driver_name = (iface->dev.driver
250 				? iface->dev.driver->name
251 				: "(none)");
252 	start += sprintf(start, format_iface,
253 			 desc->bInterfaceNumber,
254 			 desc->bAlternateSetting,
255 			 desc->bNumEndpoints,
256 			 desc->bInterfaceClass,
257 			 class_decode(desc->bInterfaceClass),
258 			 desc->bInterfaceSubClass,
259 			 desc->bInterfaceProtocol,
260 			 driver_name);
261 	up_read(&usb_bus_type.subsys.rwsem);
262 	return start;
263 }
264 
265 static char *usb_dump_interface(
266 	int speed,
267 	char *start,
268 	char *end,
269 	const struct usb_interface_cache *intfc,
270 	const struct usb_interface *iface,
271 	int setno
272 ) {
273 	const struct usb_host_interface *desc = &intfc->altsetting[setno];
274 	int i;
275 
276 	start = usb_dump_interface_descriptor(start, end, intfc, iface, setno);
277 	for (i = 0; i < desc->desc.bNumEndpoints; i++) {
278 		if (start > end)
279 			return start;
280 		start = usb_dump_endpoint_descriptor(speed,
281 				start, end, &desc->endpoint[i].desc);
282 	}
283 	return start;
284 }
285 
286 /* TBD:
287  * 0. TBDs
288  * 1. marking active interface altsettings (code lists all, but should mark
289  *    which ones are active, if any)
290  */
291 
292 static char *usb_dump_config_descriptor(char *start, char *end, const struct usb_config_descriptor *desc, int active)
293 {
294 	if (start > end)
295 		return start;
296 	start += sprintf(start, format_config,
297 			 active ? '*' : ' ',	/* mark active/actual/current cfg. */
298 			 desc->bNumInterfaces,
299 			 desc->bConfigurationValue,
300 			 desc->bmAttributes,
301 			 desc->bMaxPower * 2);
302 	return start;
303 }
304 
305 static char *usb_dump_config (
306 	int speed,
307 	char *start,
308 	char *end,
309 	const struct usb_host_config *config,
310 	int active
311 )
312 {
313 	int i, j;
314 	struct usb_interface_cache *intfc;
315 	struct usb_interface *interface;
316 
317 	if (start > end)
318 		return start;
319 	if (!config)		/* getting these some in 2.3.7; none in 2.3.6 */
320 		return start + sprintf(start, "(null Cfg. desc.)\n");
321 	start = usb_dump_config_descriptor(start, end, &config->desc, active);
322 	for (i = 0; i < config->desc.bNumInterfaces; i++) {
323 		intfc = config->intf_cache[i];
324 		interface = config->interface[i];
325 		for (j = 0; j < intfc->num_altsetting; j++) {
326 			if (start > end)
327 				return start;
328 			start = usb_dump_interface(speed,
329 				start, end, intfc, interface, j);
330 		}
331 	}
332 	return start;
333 }
334 
335 /*
336  * Dump the different USB descriptors.
337  */
338 static char *usb_dump_device_descriptor(char *start, char *end, const struct usb_device_descriptor *desc)
339 {
340 	u16 bcdUSB = le16_to_cpu(desc->bcdUSB);
341 	u16 bcdDevice = le16_to_cpu(desc->bcdDevice);
342 
343 	if (start > end)
344 		return start;
345 	start += sprintf (start, format_device1,
346 			  bcdUSB >> 8, bcdUSB & 0xff,
347 			  desc->bDeviceClass,
348 			  class_decode (desc->bDeviceClass),
349 			  desc->bDeviceSubClass,
350 			  desc->bDeviceProtocol,
351 			  desc->bMaxPacketSize0,
352 			  desc->bNumConfigurations);
353 	if (start > end)
354 		return start;
355 	start += sprintf(start, format_device2,
356 			 le16_to_cpu(desc->idVendor),
357 			 le16_to_cpu(desc->idProduct),
358 			 bcdDevice >> 8, bcdDevice & 0xff);
359 	return start;
360 }
361 
362 /*
363  * Dump the different strings that this device holds.
364  */
365 static char *usb_dump_device_strings (char *start, char *end, struct usb_device *dev)
366 {
367 	if (start > end)
368 		return start;
369 	if (dev->manufacturer)
370 		start += sprintf(start, format_string_manufacturer, dev->manufacturer);
371 	if (start > end)
372 		goto out;
373 	if (dev->product)
374 		start += sprintf(start, format_string_product, dev->product);
375 	if (start > end)
376 		goto out;
377 #ifdef ALLOW_SERIAL_NUMBER
378 	if (dev->serial)
379 		start += sprintf(start, format_string_serialnumber, dev->serial);
380 #endif
381  out:
382 	return start;
383 }
384 
385 static char *usb_dump_desc(char *start, char *end, struct usb_device *dev)
386 {
387 	int i;
388 
389 	if (start > end)
390 		return start;
391 
392 	start = usb_dump_device_descriptor(start, end, &dev->descriptor);
393 
394 	if (start > end)
395 		return start;
396 
397 	start = usb_dump_device_strings (start, end, dev);
398 
399 	for (i = 0; i < dev->descriptor.bNumConfigurations; i++) {
400 		if (start > end)
401 			return start;
402 		start = usb_dump_config(dev->speed,
403 				start, end, dev->config + i,
404 				/* active ? */
405 				(dev->config + i) == dev->actconfig);
406 	}
407 	return start;
408 }
409 
410 
411 #ifdef PROC_EXTRA /* TBD: may want to add this code later */
412 
413 static char *usb_dump_hub_descriptor(char *start, char *end, const struct usb_hub_descriptor * desc)
414 {
415 	int leng = USB_DT_HUB_NONVAR_SIZE;
416 	unsigned char *ptr = (unsigned char *)desc;
417 
418 	if (start > end)
419 		return start;
420 	start += sprintf(start, "Interface:");
421 	while (leng && start <= end) {
422 		start += sprintf(start, " %02x", *ptr);
423 		ptr++; leng--;
424 	}
425 	*start++ = '\n';
426 	return start;
427 }
428 
429 static char *usb_dump_string(char *start, char *end, const struct usb_device *dev, char *id, int index)
430 {
431 	if (start > end)
432 		return start;
433 	start += sprintf(start, "Interface:");
434 	if (index <= dev->maxstring && dev->stringindex && dev->stringindex[index])
435 		start += sprintf(start, "%s: %.100s ", id, dev->stringindex[index]);
436 	return start;
437 }
438 
439 #endif /* PROC_EXTRA */
440 
441 /*****************************************************************/
442 
443 /* This is a recursive function. Parameters:
444  * buffer - the user-space buffer to write data into
445  * nbytes - the maximum number of bytes to write
446  * skip_bytes - the number of bytes to skip before writing anything
447  * file_offset - the offset into the devices file on completion
448  * The caller must own the device lock.
449  */
450 static ssize_t usb_device_dump(char __user **buffer, size_t *nbytes, loff_t *skip_bytes, loff_t *file_offset,
451 				struct usb_device *usbdev, struct usb_bus *bus, int level, int index, int count)
452 {
453 	int chix;
454 	int ret, cnt = 0;
455 	int parent_devnum = 0;
456 	char *pages_start, *data_end, *speed;
457 	unsigned int length;
458 	ssize_t total_written = 0;
459 
460 	/* don't bother with anything else if we're not writing any data */
461 	if (*nbytes <= 0)
462 		return 0;
463 
464 	if (level > MAX_TOPO_LEVEL)
465 		return 0;
466 	/* allocate 2^1 pages = 8K (on i386); should be more than enough for one device */
467         if (!(pages_start = (char*) __get_free_pages(GFP_KERNEL,1)))
468                 return -ENOMEM;
469 
470 	if (usbdev->parent && usbdev->parent->devnum != -1)
471 		parent_devnum = usbdev->parent->devnum;
472 	/*
473 	 * So the root hub's parent is 0 and any device that is
474 	 * plugged into the root hub has a parent of 0.
475 	 */
476 	switch (usbdev->speed) {
477 	case USB_SPEED_LOW:
478 		speed = "1.5"; break;
479 	case USB_SPEED_UNKNOWN:		/* usb 1.1 root hub code */
480 	case USB_SPEED_FULL:
481 		speed = "12 "; break;
482 	case USB_SPEED_HIGH:
483 		speed = "480"; break;
484 	default:
485 		speed = "?? ";
486 	}
487 	data_end = pages_start + sprintf(pages_start, format_topo,
488 			bus->busnum, level, parent_devnum,
489 			index, count, usbdev->devnum,
490 			speed, usbdev->maxchild);
491 	/*
492 	 * level = topology-tier level;
493 	 * parent_devnum = parent device number;
494 	 * index = parent's connector number;
495 	 * count = device count at this level
496 	 */
497 	/* If this is the root hub, display the bandwidth information */
498 	if (level == 0) {
499 		int	max;
500 
501 		/* high speed reserves 80%, full/low reserves 90% */
502 		if (usbdev->speed == USB_SPEED_HIGH)
503 			max = 800;
504 		else
505 			max = FRAME_TIME_MAX_USECS_ALLOC;
506 
507 		/* report "average" periodic allocation over a microsecond.
508 		 * the schedules are actually bursty, HCDs need to deal with
509 		 * that and just compute/report this average.
510 		 */
511 		data_end += sprintf(data_end, format_bandwidth,
512 				bus->bandwidth_allocated, max,
513 				(100 * bus->bandwidth_allocated + max / 2)
514 					/ max,
515 			         bus->bandwidth_int_reqs,
516 				 bus->bandwidth_isoc_reqs);
517 
518 	}
519 	data_end = usb_dump_desc(data_end, pages_start + (2 * PAGE_SIZE) - 256, usbdev);
520 
521 	if (data_end > (pages_start + (2 * PAGE_SIZE) - 256))
522 		data_end += sprintf(data_end, "(truncated)\n");
523 
524 	length = data_end - pages_start;
525 	/* if we can start copying some data to the user */
526 	if (length > *skip_bytes) {
527 		length -= *skip_bytes;
528 		if (length > *nbytes)
529 			length = *nbytes;
530 		if (copy_to_user(*buffer, pages_start + *skip_bytes, length)) {
531 			free_pages((unsigned long)pages_start, 1);
532 			return -EFAULT;
533 		}
534 		*nbytes -= length;
535 		*file_offset += length;
536 		total_written += length;
537 		*buffer += length;
538 		*skip_bytes = 0;
539 	} else
540 		*skip_bytes -= length;
541 
542 	free_pages((unsigned long)pages_start, 1);
543 
544 	/* Now look at all of this device's children. */
545 	for (chix = 0; chix < usbdev->maxchild; chix++) {
546 		struct usb_device *childdev = usbdev->children[chix];
547 
548 		if (childdev) {
549 			usb_lock_device(childdev);
550 			ret = usb_device_dump(buffer, nbytes, skip_bytes, file_offset, childdev,
551 					bus, level + 1, chix, ++cnt);
552 			usb_unlock_device(childdev);
553 			if (ret == -EFAULT)
554 				return total_written;
555 			total_written += ret;
556 		}
557 	}
558 	return total_written;
559 }
560 
561 static ssize_t usb_device_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
562 {
563 	struct usb_bus *bus;
564 	ssize_t ret, total_written = 0;
565 	loff_t skip_bytes = *ppos;
566 
567 	if (*ppos < 0)
568 		return -EINVAL;
569 	if (nbytes <= 0)
570 		return 0;
571 	if (!access_ok(VERIFY_WRITE, buf, nbytes))
572 		return -EFAULT;
573 
574 	mutex_lock(&usb_bus_list_lock);
575 	/* print devices for all busses */
576 	list_for_each_entry(bus, &usb_bus_list, bus_list) {
577 		/* recurse through all children of the root hub */
578 		if (!bus->root_hub)
579 			continue;
580 		usb_lock_device(bus->root_hub);
581 		ret = usb_device_dump(&buf, &nbytes, &skip_bytes, ppos, bus->root_hub, bus, 0, 0, 0);
582 		usb_unlock_device(bus->root_hub);
583 		if (ret < 0) {
584 			mutex_unlock(&usb_bus_list_lock);
585 			return ret;
586 		}
587 		total_written += ret;
588 	}
589 	mutex_unlock(&usb_bus_list_lock);
590 	return total_written;
591 }
592 
593 /* Kernel lock for "lastev" protection */
594 static unsigned int usb_device_poll(struct file *file, struct poll_table_struct *wait)
595 {
596 	struct usb_device_status *st = (struct usb_device_status *)file->private_data;
597 	unsigned int mask = 0;
598 
599 	lock_kernel();
600 	if (!st) {
601 		st = kmalloc(sizeof(struct usb_device_status), GFP_KERNEL);
602 		if (!st) {
603 			unlock_kernel();
604 			return POLLIN;
605 		}
606 
607 		/* we may have dropped BKL - need to check for having lost the race */
608 		if (file->private_data) {
609 			kfree(st);
610 			st = file->private_data;
611 			goto lost_race;
612 		}
613 
614 		/*
615 		 * need to prevent the module from being unloaded, since
616 		 * proc_unregister does not call the release method and
617 		 * we would have a memory leak
618 		 */
619 		st->lastev = conndiscevcnt;
620 		file->private_data = st;
621 		mask = POLLIN;
622 	}
623 lost_race:
624 	if (file->f_mode & FMODE_READ)
625                 poll_wait(file, &deviceconndiscwq, wait);
626 	if (st->lastev != conndiscevcnt)
627 		mask |= POLLIN;
628 	st->lastev = conndiscevcnt;
629 	unlock_kernel();
630 	return mask;
631 }
632 
633 static int usb_device_open(struct inode *inode, struct file *file)
634 {
635         file->private_data = NULL;
636         return 0;
637 }
638 
639 static int usb_device_release(struct inode *inode, struct file *file)
640 {
641 	kfree(file->private_data);
642 	file->private_data = NULL;
643         return 0;
644 }
645 
646 static loff_t usb_device_lseek(struct file * file, loff_t offset, int orig)
647 {
648 	loff_t ret;
649 
650 	lock_kernel();
651 
652 	switch (orig) {
653 	case 0:
654 		file->f_pos = offset;
655 		ret = file->f_pos;
656 		break;
657 	case 1:
658 		file->f_pos += offset;
659 		ret = file->f_pos;
660 		break;
661 	case 2:
662 	default:
663 		ret = -EINVAL;
664 	}
665 
666 	unlock_kernel();
667 	return ret;
668 }
669 
670 struct file_operations usbfs_devices_fops = {
671 	.llseek =	usb_device_lseek,
672 	.read =		usb_device_read,
673 	.poll =		usb_device_poll,
674 	.open =		usb_device_open,
675 	.release =	usb_device_release,
676 };
677