xref: /freebsd/sys/dev/usb/usb_hid.c (revision 5861f9665471e98e544f6fa3ce73c4912229ff82)
1 /*	$NetBSD: hid.c,v 1.17 2001/11/13 06:24:53 lukem Exp $	*/
2 
3 
4 #include <sys/cdefs.h>
5 __FBSDID("$FreeBSD$");
6 /*-
7  * Copyright (c) 1998 The NetBSD Foundation, Inc.
8  * All rights reserved.
9  *
10  * This code is derived from software contributed to The NetBSD Foundation
11  * by Lennart Augustsson (lennart@augustsson.net) at
12  * Carlstedt Research & Technology.
13  *
14  * Redistribution and use in source and binary forms, with or without
15  * modification, are permitted provided that the following conditions
16  * are met:
17  * 1. Redistributions of source code must retain the above copyright
18  *    notice, this list of conditions and the following disclaimer.
19  * 2. Redistributions in binary form must reproduce the above copyright
20  *    notice, this list of conditions and the following disclaimer in the
21  *    documentation and/or other materials provided with the distribution.
22  * 3. All advertising materials mentioning features or use of this software
23  *    must display the following acknowledgement:
24  *        This product includes software developed by the NetBSD
25  *        Foundation, Inc. and its contributors.
26  * 4. Neither the name of The NetBSD Foundation nor the names of its
27  *    contributors may be used to endorse or promote products derived
28  *    from this software without specific prior written permission.
29  *
30  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
31  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
32  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
33  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
34  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
35  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
36  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
37  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
38  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
39  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
40  * POSSIBILITY OF SUCH DAMAGE.
41  */
42 
43 #include <sys/stdint.h>
44 #include <sys/stddef.h>
45 #include <sys/param.h>
46 #include <sys/queue.h>
47 #include <sys/types.h>
48 #include <sys/systm.h>
49 #include <sys/kernel.h>
50 #include <sys/bus.h>
51 #include <sys/linker_set.h>
52 #include <sys/module.h>
53 #include <sys/lock.h>
54 #include <sys/mutex.h>
55 #include <sys/condvar.h>
56 #include <sys/sysctl.h>
57 #include <sys/sx.h>
58 #include <sys/unistd.h>
59 #include <sys/callout.h>
60 #include <sys/malloc.h>
61 #include <sys/priv.h>
62 
63 #include <dev/usb/usb.h>
64 #include <dev/usb/usbdi.h>
65 #include <dev/usb/usbdi_util.h>
66 #include <dev/usb/usbhid.h>
67 
68 #define	USB_DEBUG_VAR usb_debug
69 
70 #include <dev/usb/usb_core.h>
71 #include <dev/usb/usb_debug.h>
72 #include <dev/usb/usb_process.h>
73 #include <dev/usb/usb_device.h>
74 #include <dev/usb/usb_request.h>
75 
76 static void hid_clear_local(struct hid_item *);
77 static uint8_t hid_get_byte(struct hid_data *s, const uint16_t wSize);
78 
79 #define	MAXUSAGE 64
80 #define	MAXPUSH 4
81 struct hid_data {
82 	const uint8_t *start;
83 	const uint8_t *end;
84 	const uint8_t *p;
85 	struct hid_item cur[MAXPUSH];
86 	int32_t	usages_min[MAXUSAGE];
87 	int32_t	usages_max[MAXUSAGE];
88 	int32_t usage_last;	/* last seen usage */
89 	uint32_t loc_size;	/* last seen size */
90 	uint32_t loc_count;	/* last seen count */
91 	uint8_t	kindset;	/* we have 5 kinds so 8 bits are enough */
92 	uint8_t	pushlevel;	/* current pushlevel */
93 	uint8_t	ncount;		/* end usage item count */
94 	uint8_t icount;		/* current usage item count */
95 	uint8_t	nusage;		/* end "usages_min/max" index */
96 	uint8_t	iusage;		/* current "usages_min/max" index */
97 	uint8_t ousage;		/* current "usages_min/max" offset */
98 	uint8_t	susage;		/* usage set flags */
99 };
100 
101 /*------------------------------------------------------------------------*
102  *	hid_clear_local
103  *------------------------------------------------------------------------*/
104 static void
105 hid_clear_local(struct hid_item *c)
106 {
107 
108 	c->loc.count = 0;
109 	c->loc.size = 0;
110 	c->usage = 0;
111 	c->usage_minimum = 0;
112 	c->usage_maximum = 0;
113 	c->designator_index = 0;
114 	c->designator_minimum = 0;
115 	c->designator_maximum = 0;
116 	c->string_index = 0;
117 	c->string_minimum = 0;
118 	c->string_maximum = 0;
119 	c->set_delimiter = 0;
120 }
121 
122 /*------------------------------------------------------------------------*
123  *	hid_start_parse
124  *------------------------------------------------------------------------*/
125 struct hid_data *
126 hid_start_parse(const void *d, usb_size_t len, int kindset)
127 {
128 	struct hid_data *s;
129 
130 	if ((kindset-1) & kindset) {
131 		DPRINTFN(0, "Only one bit can be "
132 		    "set in the kindset\n");
133 		return (NULL);
134 	}
135 
136 	s = malloc(sizeof *s, M_TEMP, M_WAITOK | M_ZERO);
137 	s->start = s->p = d;
138 	s->end = ((const uint8_t *)d) + len;
139 	s->kindset = kindset;
140 	return (s);
141 }
142 
143 /*------------------------------------------------------------------------*
144  *	hid_end_parse
145  *------------------------------------------------------------------------*/
146 void
147 hid_end_parse(struct hid_data *s)
148 {
149 	if (s == NULL)
150 		return;
151 
152 	free(s, M_TEMP);
153 }
154 
155 /*------------------------------------------------------------------------*
156  *	get byte from HID descriptor
157  *------------------------------------------------------------------------*/
158 static uint8_t
159 hid_get_byte(struct hid_data *s, const uint16_t wSize)
160 {
161 	const uint8_t *ptr;
162 	uint8_t retval;
163 
164 	ptr = s->p;
165 
166 	/* check if end is reached */
167 	if (ptr == s->end)
168 		return (0);
169 
170 	/* read out a byte */
171 	retval = *ptr;
172 
173 	/* check if data pointer can be advanced by "wSize" bytes */
174 	if ((s->end - ptr) < wSize)
175 		ptr = s->end;
176 	else
177 		ptr += wSize;
178 
179 	/* update pointer */
180 	s->p = ptr;
181 
182 	return (retval);
183 }
184 
185 /*------------------------------------------------------------------------*
186  *	hid_get_item
187  *------------------------------------------------------------------------*/
188 int
189 hid_get_item(struct hid_data *s, struct hid_item *h)
190 {
191 	struct hid_item *c;
192 	unsigned int bTag, bType, bSize;
193 	uint32_t oldpos;
194 	int32_t mask;
195 	int32_t dval;
196 
197 	if (s == NULL)
198 		return (0);
199 
200 	c = &s->cur[s->pushlevel];
201 
202  top:
203 	/* check if there is an array of items */
204 	if (s->icount < s->ncount) {
205 		/* get current usage */
206 		if (s->iusage < s->nusage) {
207 			dval = s->usages_min[s->iusage] + s->ousage;
208 			c->usage = dval;
209 			s->usage_last = dval;
210 			if (dval == s->usages_max[s->iusage]) {
211 				s->iusage ++;
212 				s->ousage = 0;
213 			} else {
214 				s->ousage ++;
215 			}
216 		} else {
217 			DPRINTFN(1, "Using last usage\n");
218 			dval = s->usage_last;
219 		}
220 		s->icount ++;
221 		/*
222 		 * Only copy HID item, increment position and return
223 		 * if correct kindset!
224 		 */
225 		if (s->kindset & (1 << c->kind)) {
226 			*h = *c;
227 			DPRINTFN(1, "%u,%u,%u\n", h->loc.pos,
228 			    h->loc.size, h->loc.count);
229 			c->loc.pos += c->loc.size * c->loc.count;
230 			return (1);
231 		}
232 	}
233 
234 	/* reset state variables */
235 	s->icount = 0;
236 	s->ncount = 0;
237 	s->iusage = 0;
238 	s->nusage = 0;
239 	s->susage = 0;
240 	s->ousage = 0;
241 	hid_clear_local(c);
242 
243 	/* get next item */
244 	while (s->p != s->end) {
245 
246 		bSize = hid_get_byte(s, 1);
247 		if (bSize == 0xfe) {
248 			/* long item */
249 			bSize = hid_get_byte(s, 1);
250 			bSize |= hid_get_byte(s, 1) << 8;
251 			bTag = hid_get_byte(s, 1);
252 			bType = 0xff;	/* XXX what should it be */
253 		} else {
254 			/* short item */
255 			bTag = bSize >> 4;
256 			bType = (bSize >> 2) & 3;
257 			bSize &= 3;
258 			if (bSize == 3)
259 				bSize = 4;
260 		}
261 		switch (bSize) {
262 		case 0:
263 			dval = 0;
264 			mask = 0;
265 			break;
266 		case 1:
267 			dval = (int8_t)hid_get_byte(s, 1);
268 			mask = 0xFF;
269 			break;
270 		case 2:
271 			dval = hid_get_byte(s, 1);
272 			dval |= hid_get_byte(s, 1) << 8;
273 			dval = (int16_t)dval;
274 			mask = 0xFFFF;
275 			break;
276 		case 4:
277 			dval = hid_get_byte(s, 1);
278 			dval |= hid_get_byte(s, 1) << 8;
279 			dval |= hid_get_byte(s, 1) << 16;
280 			dval |= hid_get_byte(s, 1) << 24;
281 			mask = 0xFFFFFFFF;
282 			break;
283 		default:
284 			dval = hid_get_byte(s, bSize);
285 			DPRINTFN(0, "bad length %u (data=0x%02x)\n",
286 			    bSize, dval);
287 			continue;
288 		}
289 
290 		switch (bType) {
291 		case 0:		/* Main */
292 			switch (bTag) {
293 			case 8:	/* Input */
294 				c->kind = hid_input;
295 				c->flags = dval;
296 		ret:
297 				c->loc.count = s->loc_count;
298 				c->loc.size = s->loc_size;
299 
300 				if (c->flags & HIO_VARIABLE) {
301 					/* range check usage count */
302 					if (c->loc.count > 255) {
303 						DPRINTFN(0, "Number of "
304 						    "items truncated to 255\n");
305 						s->ncount = 255;
306 					} else
307 						s->ncount = c->loc.count;
308 
309 					/*
310 					 * The "top" loop will return
311 					 * one and one item:
312 					 */
313 					c->loc.count = 1;
314 				} else {
315 					s->ncount = 1;
316 				}
317 				goto top;
318 
319 			case 9:	/* Output */
320 				c->kind = hid_output;
321 				c->flags = dval;
322 				goto ret;
323 			case 10:	/* Collection */
324 				c->kind = hid_collection;
325 				c->collection = dval;
326 				c->collevel++;
327 				c->usage = s->usage_last;
328 				*h = *c;
329 				return (1);
330 			case 11:	/* Feature */
331 				c->kind = hid_feature;
332 				c->flags = dval;
333 				goto ret;
334 			case 12:	/* End collection */
335 				c->kind = hid_endcollection;
336 				if (c->collevel == 0) {
337 					DPRINTFN(0, "invalid end collection\n");
338 					return (0);
339 				}
340 				c->collevel--;
341 				*h = *c;
342 				return (1);
343 			default:
344 				DPRINTFN(0, "Main bTag=%d\n", bTag);
345 				break;
346 			}
347 			break;
348 		case 1:		/* Global */
349 			switch (bTag) {
350 			case 0:
351 				c->_usage_page = dval << 16;
352 				break;
353 			case 1:
354 				c->logical_minimum = dval;
355 				break;
356 			case 2:
357 				c->logical_maximum = dval;
358 				break;
359 			case 3:
360 				c->physical_minimum = dval;
361 				break;
362 			case 4:
363 				c->physical_maximum = dval;
364 				break;
365 			case 5:
366 				c->unit_exponent = dval;
367 				break;
368 			case 6:
369 				c->unit = dval;
370 				break;
371 			case 7:
372 				/* mask because value is unsigned */
373 				s->loc_size = dval & mask;
374 				break;
375 			case 8:
376 				c->report_ID = dval;
377 				/* new report - reset position */
378 				c->loc.pos = 0;
379 				break;
380 			case 9:
381 				/* mask because value is unsigned */
382 				s->loc_count = dval & mask;
383 				break;
384 			case 10:	/* Push */
385 				s->pushlevel ++;
386 				if (s->pushlevel < MAXPUSH) {
387 					s->cur[s->pushlevel] = *c;
388 					/* store size and count */
389 					c->loc.size = s->loc_size;
390 					c->loc.count = s->loc_count;
391 					/* update current item pointer */
392 					c = &s->cur[s->pushlevel];
393 				} else {
394 					DPRINTFN(0, "Cannot push "
395 					    "item @ %d!\n", s->pushlevel);
396 				}
397 				break;
398 			case 11:	/* Pop */
399 				s->pushlevel --;
400 				if (s->pushlevel < MAXPUSH) {
401 					/* preserve position */
402 					oldpos = c->loc.pos;
403 					c = &s->cur[s->pushlevel];
404 					/* restore size and count */
405 					s->loc_size = c->loc.size;
406 					s->loc_count = c->loc.count;
407 					/* set default item location */
408 					c->loc.pos = oldpos;
409 					c->loc.size = 0;
410 					c->loc.count = 0;
411 				} else {
412 					DPRINTFN(0, "Cannot pop "
413 					    "item @ %d!\n", s->pushlevel);
414 				}
415 				break;
416 			default:
417 				DPRINTFN(0, "Global bTag=%d\n", bTag);
418 				break;
419 			}
420 			break;
421 		case 2:		/* Local */
422 			switch (bTag) {
423 			case 0:
424 				if (bSize != 4)
425 					dval = (dval & mask) | c->_usage_page;
426 
427 				/* set last usage, in case of a collection */
428 				s->usage_last = dval;
429 
430 				if (s->nusage < MAXUSAGE) {
431 					s->usages_min[s->nusage] = dval;
432 					s->usages_max[s->nusage] = dval;
433 					s->nusage ++;
434 				} else {
435 					DPRINTFN(0, "max usage reached!\n");
436 				}
437 
438 				/* clear any pending usage sets */
439 				s->susage = 0;
440 				break;
441 			case 1:
442 				s->susage |= 1;
443 
444 				if (bSize != 4)
445 					dval = (dval & mask) | c->_usage_page;
446 				c->usage_minimum = dval;
447 
448 				goto check_set;
449 			case 2:
450 				s->susage |= 2;
451 
452 				if (bSize != 4)
453 					dval = (dval & mask) | c->_usage_page;
454 				c->usage_maximum = dval;
455 
456 			check_set:
457 				if (s->susage != 3)
458 					break;
459 
460 				/* sanity check */
461 				if ((s->nusage < MAXUSAGE) &&
462 				    (c->usage_minimum <= c->usage_maximum)) {
463 					/* add usage range */
464 					s->usages_min[s->nusage] =
465 					    c->usage_minimum;
466 					s->usages_max[s->nusage] =
467 					    c->usage_maximum;
468 					s->nusage ++;
469 				} else {
470 					DPRINTFN(0, "Usage set dropped!\n");
471 				}
472 				s->susage = 0;
473 				break;
474 			case 3:
475 				c->designator_index = dval;
476 				break;
477 			case 4:
478 				c->designator_minimum = dval;
479 				break;
480 			case 5:
481 				c->designator_maximum = dval;
482 				break;
483 			case 7:
484 				c->string_index = dval;
485 				break;
486 			case 8:
487 				c->string_minimum = dval;
488 				break;
489 			case 9:
490 				c->string_maximum = dval;
491 				break;
492 			case 10:
493 				c->set_delimiter = dval;
494 				break;
495 			default:
496 				DPRINTFN(0, "Local bTag=%d\n", bTag);
497 				break;
498 			}
499 			break;
500 		default:
501 			DPRINTFN(0, "default bType=%d\n", bType);
502 			break;
503 		}
504 	}
505 	return (0);
506 }
507 
508 /*------------------------------------------------------------------------*
509  *	hid_report_size
510  *------------------------------------------------------------------------*/
511 int
512 hid_report_size(const void *buf, usb_size_t len, enum hid_kind k, uint8_t *id)
513 {
514 	struct hid_data *d;
515 	struct hid_item h;
516 	uint32_t temp;
517 	uint32_t hpos;
518 	uint32_t lpos;
519 	uint8_t any_id;
520 
521 	any_id = 0;
522 	hpos = 0;
523 	lpos = 0xFFFFFFFF;
524 
525 	for (d = hid_start_parse(buf, len, 1 << k); hid_get_item(d, &h);) {
526 		if (h.kind == k) {
527 			/* check for ID-byte presense */
528 			if ((h.report_ID != 0) && !any_id) {
529 				if (id != NULL)
530 					*id = h.report_ID;
531 				any_id = 1;
532 			}
533 			/* compute minimum */
534 			if (lpos > h.loc.pos)
535 				lpos = h.loc.pos;
536 			/* compute end position */
537 			temp = h.loc.pos + (h.loc.size * h.loc.count);
538 			/* compute maximum */
539 			if (hpos < temp)
540 				hpos = temp;
541 		}
542 	}
543 	hid_end_parse(d);
544 
545 	/* safety check - can happen in case of currupt descriptors */
546 	if (lpos > hpos)
547 		temp = 0;
548 	else
549 		temp = hpos - lpos;
550 
551 	/* check for ID byte */
552 	if (any_id)
553 		temp += 8;
554 	else if (id != NULL)
555 		*id = 0;
556 
557 	/* return length in bytes rounded up */
558 	return ((temp + 7) / 8);
559 }
560 
561 /*------------------------------------------------------------------------*
562  *	hid_locate
563  *------------------------------------------------------------------------*/
564 int
565 hid_locate(const void *desc, usb_size_t size, uint32_t u, enum hid_kind k,
566     uint8_t index, struct hid_location *loc, uint32_t *flags, uint8_t *id)
567 {
568 	struct hid_data *d;
569 	struct hid_item h;
570 
571 	for (d = hid_start_parse(desc, size, 1 << k); hid_get_item(d, &h);) {
572 		if (h.kind == k && !(h.flags & HIO_CONST) && h.usage == u) {
573 			if (index--)
574 				continue;
575 			if (loc != NULL)
576 				*loc = h.loc;
577 			if (flags != NULL)
578 				*flags = h.flags;
579 			if (id != NULL)
580 				*id = h.report_ID;
581 			hid_end_parse(d);
582 			return (1);
583 		}
584 	}
585 	if (loc != NULL)
586 		loc->size = 0;
587 	if (flags != NULL)
588 		*flags = 0;
589 	if (id != NULL)
590 		*id = 0;
591 	hid_end_parse(d);
592 	return (0);
593 }
594 
595 /*------------------------------------------------------------------------*
596  *	hid_get_data
597  *------------------------------------------------------------------------*/
598 uint32_t
599 hid_get_data(const uint8_t *buf, usb_size_t len, struct hid_location *loc)
600 {
601 	uint32_t hpos = loc->pos;
602 	uint32_t hsize = loc->size;
603 	uint32_t data;
604 	uint32_t rpos;
605 	uint8_t n;
606 
607 	DPRINTFN(11, "hid_get_data: loc %d/%d\n", hpos, hsize);
608 
609 	/* Range check and limit */
610 	if (hsize == 0)
611 		return (0);
612 	if (hsize > 32)
613 		hsize = 32;
614 
615 	/* Get data in a safe way */
616 	data = 0;
617 	rpos = (hpos / 8);
618 	n = (hsize + 7) / 8;
619 	rpos += n;
620 	while (n--) {
621 		rpos--;
622 		if (rpos < len)
623 			data |= buf[rpos] << (8 * n);
624 	}
625 
626 	/* Correctly shift down data */
627 	data = (data >> (hpos % 8));
628 
629 	/* Mask and sign extend in one */
630 	n = 32 - hsize;
631 	data = ((int32_t)data << n) >> n;
632 
633 	DPRINTFN(11, "hid_get_data: loc %d/%d = %lu\n",
634 	    loc->pos, loc->size, (long)data);
635 	return (data);
636 }
637 
638 /*------------------------------------------------------------------------*
639  *	hid_is_collection
640  *------------------------------------------------------------------------*/
641 int
642 hid_is_collection(const void *desc, usb_size_t size, uint32_t usage)
643 {
644 	struct hid_data *hd;
645 	struct hid_item hi;
646 	int err;
647 
648 	hd = hid_start_parse(desc, size, hid_input);
649 	if (hd == NULL)
650 		return (0);
651 
652 	while ((err = hid_get_item(hd, &hi))) {
653 		 if (hi.kind == hid_collection &&
654 		     hi.usage == usage)
655 			break;
656 	}
657 	hid_end_parse(hd);
658 	return (err);
659 }
660 
661 /*------------------------------------------------------------------------*
662  *	hid_get_descriptor_from_usb
663  *
664  * This function will search for a HID descriptor between two USB
665  * interface descriptors.
666  *
667  * Return values:
668  * NULL: No more HID descriptors.
669  * Else: Pointer to HID descriptor.
670  *------------------------------------------------------------------------*/
671 struct usb_hid_descriptor *
672 hid_get_descriptor_from_usb(struct usb_config_descriptor *cd,
673     struct usb_interface_descriptor *id)
674 {
675 	struct usb_descriptor *desc = (void *)id;
676 
677 	if (desc == NULL) {
678 		return (NULL);
679 	}
680 	while ((desc = usb_desc_foreach(cd, desc))) {
681 		if ((desc->bDescriptorType == UDESC_HID) &&
682 		    (desc->bLength >= USB_HID_DESCRIPTOR_SIZE(0))) {
683 			return (void *)desc;
684 		}
685 		if (desc->bDescriptorType == UDESC_INTERFACE) {
686 			break;
687 		}
688 	}
689 	return (NULL);
690 }
691 
692 /*------------------------------------------------------------------------*
693  *	usbd_req_get_hid_desc
694  *
695  * This function will read out an USB report descriptor from the USB
696  * device.
697  *
698  * Return values:
699  * NULL: Failure.
700  * Else: Success. The pointer should eventually be passed to free().
701  *------------------------------------------------------------------------*/
702 usb_error_t
703 usbd_req_get_hid_desc(struct usb_device *udev, struct mtx *mtx,
704     void **descp, uint16_t *sizep,
705     struct malloc_type *mem, uint8_t iface_index)
706 {
707 	struct usb_interface *iface = usbd_get_iface(udev, iface_index);
708 	struct usb_hid_descriptor *hid;
709 	usb_error_t err;
710 
711 	if ((iface == NULL) || (iface->idesc == NULL)) {
712 		return (USB_ERR_INVAL);
713 	}
714 	hid = hid_get_descriptor_from_usb
715 	    (usbd_get_config_descriptor(udev), iface->idesc);
716 
717 	if (hid == NULL) {
718 		return (USB_ERR_IOERROR);
719 	}
720 	*sizep = UGETW(hid->descrs[0].wDescriptorLength);
721 	if (*sizep == 0) {
722 		return (USB_ERR_IOERROR);
723 	}
724 	if (mtx)
725 		mtx_unlock(mtx);
726 
727 	*descp = malloc(*sizep, mem, M_ZERO | M_WAITOK);
728 
729 	if (mtx)
730 		mtx_lock(mtx);
731 
732 	if (*descp == NULL) {
733 		return (USB_ERR_NOMEM);
734 	}
735 	err = usbd_req_get_report_descriptor
736 	    (udev, mtx, *descp, *sizep, iface_index);
737 
738 	if (err) {
739 		free(*descp, mem);
740 		*descp = NULL;
741 		return (err);
742 	}
743 	return (USB_ERR_NORMAL_COMPLETION);
744 }
745