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usbdi_util.c revision 1.56
      1 /*	$NetBSD: usbdi_util.c,v 1.56 2012/03/06 03:35:30 mrg Exp $	*/
      2 
      3 /*
      4  * Copyright (c) 1998 The NetBSD Foundation, Inc.
      5  * All rights reserved.
      6  *
      7  * This code is derived from software contributed to The NetBSD Foundation
      8  * by Lennart Augustsson (lennart (at) augustsson.net) at
      9  * Carlstedt Research & Technology.
     10  *
     11  * Redistribution and use in source and binary forms, with or without
     12  * modification, are permitted provided that the following conditions
     13  * are met:
     14  * 1. Redistributions of source code must retain the above copyright
     15  *    notice, this list of conditions and the following disclaimer.
     16  * 2. Redistributions in binary form must reproduce the above copyright
     17  *    notice, this list of conditions and the following disclaimer in the
     18  *    documentation and/or other materials provided with the distribution.
     19  *
     20  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
     21  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
     22  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     23  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
     24  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
     25  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
     26  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
     27  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
     28  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
     29  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
     30  * POSSIBILITY OF SUCH DAMAGE.
     31  */
     32 
     33 #include <sys/cdefs.h>
     34 __KERNEL_RCSID(0, "$NetBSD: usbdi_util.c,v 1.56 2012/03/06 03:35:30 mrg Exp $");
     35 
     36 #include <sys/param.h>
     37 #include <sys/systm.h>
     38 #include <sys/kernel.h>
     39 #include <sys/malloc.h>
     40 #include <sys/proc.h>
     41 #include <sys/device.h>
     42 
     43 #include <dev/usb/usb.h>
     44 #include <dev/usb/usbhid.h>
     45 
     46 #include <dev/usb/usbdi.h>
     47 #include <dev/usb/usbdi_util.h>
     48 
     49 #ifdef USB_DEBUG
     50 #define DPRINTF(x)	if (usbdebug) printf x
     51 #define DPRINTFN(n,x)	if (usbdebug>(n)) printf x
     52 extern int usbdebug;
     53 #else
     54 #define DPRINTF(x)
     55 #define DPRINTFN(n,x)
     56 #endif
     57 
     58 usbd_status
     59 usbd_get_desc(usbd_device_handle dev, int type, int index, int len, void *desc)
     60 {
     61 	usb_device_request_t req;
     62 
     63 	DPRINTFN(3,("usbd_get_desc: type=%d, index=%d, len=%d\n",
     64 		    type, index, len));
     65 
     66 	req.bmRequestType = UT_READ_DEVICE;
     67 	req.bRequest = UR_GET_DESCRIPTOR;
     68 	USETW2(req.wValue, type, index);
     69 	USETW(req.wIndex, 0);
     70 	USETW(req.wLength, len);
     71 	return (usbd_do_request(dev, &req, desc));
     72 }
     73 
     74 usbd_status
     75 usbd_get_config_desc(usbd_device_handle dev, int confidx,
     76 		     usb_config_descriptor_t *d)
     77 {
     78 	usbd_status err;
     79 
     80 	DPRINTFN(3,("usbd_get_config_desc: confidx=%d\n", confidx));
     81 	err = usbd_get_desc(dev, UDESC_CONFIG, confidx,
     82 			    USB_CONFIG_DESCRIPTOR_SIZE, d);
     83 	if (err)
     84 		return (err);
     85 	if (d->bDescriptorType != UDESC_CONFIG) {
     86 		DPRINTFN(-1,("usbd_get_config_desc: confidx=%d, bad desc "
     87 			     "len=%d type=%d\n",
     88 			     confidx, d->bLength, d->bDescriptorType));
     89 		return (USBD_INVAL);
     90 	}
     91 	return (USBD_NORMAL_COMPLETION);
     92 }
     93 
     94 usbd_status
     95 usbd_get_config_desc_full(usbd_device_handle dev, int conf, void *d, int size)
     96 {
     97 	DPRINTFN(3,("usbd_get_config_desc_full: conf=%d\n", conf));
     98 	return (usbd_get_desc(dev, UDESC_CONFIG, conf, size, d));
     99 }
    100 
    101 usbd_status
    102 usbd_get_device_desc(usbd_device_handle dev, usb_device_descriptor_t *d)
    103 {
    104 	DPRINTFN(3,("usbd_get_device_desc:\n"));
    105 	return (usbd_get_desc(dev, UDESC_DEVICE,
    106 			     0, USB_DEVICE_DESCRIPTOR_SIZE, d));
    107 }
    108 
    109 usbd_status
    110 usbd_get_device_status(usbd_device_handle dev, usb_status_t *st)
    111 {
    112 	usb_device_request_t req;
    113 
    114 	req.bmRequestType = UT_READ_DEVICE;
    115 	req.bRequest = UR_GET_STATUS;
    116 	USETW(req.wValue, 0);
    117 	USETW(req.wIndex, 0);
    118 	USETW(req.wLength, sizeof(usb_status_t));
    119 	return (usbd_do_request(dev, &req, st));
    120 }
    121 
    122 usbd_status
    123 usbd_get_hub_status(usbd_device_handle dev, usb_hub_status_t *st)
    124 {
    125 	usb_device_request_t req;
    126 
    127 	req.bmRequestType = UT_READ_CLASS_DEVICE;
    128 	req.bRequest = UR_GET_STATUS;
    129 	USETW(req.wValue, 0);
    130 	USETW(req.wIndex, 0);
    131 	USETW(req.wLength, sizeof(usb_hub_status_t));
    132 	return (usbd_do_request(dev, &req, st));
    133 }
    134 
    135 usbd_status
    136 usbd_set_address(usbd_device_handle dev, int addr)
    137 {
    138 	usb_device_request_t req;
    139 
    140 	req.bmRequestType = UT_WRITE_DEVICE;
    141 	req.bRequest = UR_SET_ADDRESS;
    142 	USETW(req.wValue, addr);
    143 	USETW(req.wIndex, 0);
    144 	USETW(req.wLength, 0);
    145 	return usbd_do_request(dev, &req, 0);
    146 }
    147 
    148 usbd_status
    149 usbd_get_port_status(usbd_device_handle dev, int port, usb_port_status_t *ps)
    150 {
    151 	usb_device_request_t req;
    152 
    153 	req.bmRequestType = UT_READ_CLASS_OTHER;
    154 	req.bRequest = UR_GET_STATUS;
    155 	USETW(req.wValue, 0);
    156 	USETW(req.wIndex, port);
    157 	USETW(req.wLength, sizeof *ps);
    158 	return (usbd_do_request(dev, &req, ps));
    159 }
    160 
    161 usbd_status
    162 usbd_clear_hub_feature(usbd_device_handle dev, int sel)
    163 {
    164 	usb_device_request_t req;
    165 
    166 	req.bmRequestType = UT_WRITE_CLASS_DEVICE;
    167 	req.bRequest = UR_CLEAR_FEATURE;
    168 	USETW(req.wValue, sel);
    169 	USETW(req.wIndex, 0);
    170 	USETW(req.wLength, 0);
    171 	return (usbd_do_request(dev, &req, 0));
    172 }
    173 
    174 usbd_status
    175 usbd_set_hub_feature(usbd_device_handle dev, int sel)
    176 {
    177 	usb_device_request_t req;
    178 
    179 	req.bmRequestType = UT_WRITE_CLASS_DEVICE;
    180 	req.bRequest = UR_SET_FEATURE;
    181 	USETW(req.wValue, sel);
    182 	USETW(req.wIndex, 0);
    183 	USETW(req.wLength, 0);
    184 	return (usbd_do_request(dev, &req, 0));
    185 }
    186 
    187 usbd_status
    188 usbd_clear_port_feature(usbd_device_handle dev, int port, int sel)
    189 {
    190 	usb_device_request_t req;
    191 
    192 	req.bmRequestType = UT_WRITE_CLASS_OTHER;
    193 	req.bRequest = UR_CLEAR_FEATURE;
    194 	USETW(req.wValue, sel);
    195 	USETW(req.wIndex, port);
    196 	USETW(req.wLength, 0);
    197 	return (usbd_do_request(dev, &req, 0));
    198 }
    199 
    200 usbd_status
    201 usbd_set_port_feature(usbd_device_handle dev, int port, int sel)
    202 {
    203 	usb_device_request_t req;
    204 
    205 	req.bmRequestType = UT_WRITE_CLASS_OTHER;
    206 	req.bRequest = UR_SET_FEATURE;
    207 	USETW(req.wValue, sel);
    208 	USETW(req.wIndex, port);
    209 	USETW(req.wLength, 0);
    210 	return (usbd_do_request(dev, &req, 0));
    211 }
    212 
    213 usbd_status
    214 usbd_get_protocol(usbd_interface_handle iface, u_int8_t *report)
    215 {
    216 	usb_interface_descriptor_t *id = usbd_get_interface_descriptor(iface);
    217 	usbd_device_handle dev;
    218 	usb_device_request_t req;
    219 
    220 	DPRINTFN(4, ("usbd_get_protocol: iface=%p, endpt=%d\n",
    221 		     iface, id->bInterfaceNumber));
    222 	if (id == NULL)
    223 		return (USBD_IOERROR);
    224 	usbd_interface2device_handle(iface, &dev);
    225 	req.bmRequestType = UT_READ_CLASS_INTERFACE;
    226 	req.bRequest = UR_GET_PROTOCOL;
    227 	USETW(req.wValue, 0);
    228 	USETW(req.wIndex, id->bInterfaceNumber);
    229 	USETW(req.wLength, 1);
    230 	return (usbd_do_request(dev, &req, report));
    231 }
    232 
    233 usbd_status
    234 usbd_set_protocol(usbd_interface_handle iface, int report)
    235 {
    236 	usb_interface_descriptor_t *id = usbd_get_interface_descriptor(iface);
    237 	usbd_device_handle dev;
    238 	usb_device_request_t req;
    239 
    240 	DPRINTFN(4, ("usbd_set_protocol: iface=%p, report=%d, endpt=%d\n",
    241 		     iface, report, id->bInterfaceNumber));
    242 	if (id == NULL)
    243 		return (USBD_IOERROR);
    244 	usbd_interface2device_handle(iface, &dev);
    245 	req.bmRequestType = UT_WRITE_CLASS_INTERFACE;
    246 	req.bRequest = UR_SET_PROTOCOL;
    247 	USETW(req.wValue, report);
    248 	USETW(req.wIndex, id->bInterfaceNumber);
    249 	USETW(req.wLength, 0);
    250 	return (usbd_do_request(dev, &req, 0));
    251 }
    252 
    253 usbd_status
    254 usbd_set_report(usbd_interface_handle iface, int type, int id, void *data,
    255 		int len)
    256 {
    257 	usb_interface_descriptor_t *ifd = usbd_get_interface_descriptor(iface);
    258 	usbd_device_handle dev;
    259 	usb_device_request_t req;
    260 
    261 	DPRINTFN(4, ("usbd_set_report: len=%d\n", len));
    262 	if (ifd == NULL)
    263 		return (USBD_IOERROR);
    264 	usbd_interface2device_handle(iface, &dev);
    265 	req.bmRequestType = UT_WRITE_CLASS_INTERFACE;
    266 	req.bRequest = UR_SET_REPORT;
    267 	USETW2(req.wValue, type, id);
    268 	USETW(req.wIndex, ifd->bInterfaceNumber);
    269 	USETW(req.wLength, len);
    270 	return (usbd_do_request(dev, &req, data));
    271 }
    272 
    273 usbd_status
    274 usbd_set_report_async(usbd_interface_handle iface, int type, int id, void *data,
    275 		      int len)
    276 {
    277 	usb_interface_descriptor_t *ifd = usbd_get_interface_descriptor(iface);
    278 	usbd_device_handle dev;
    279 	usb_device_request_t req;
    280 
    281 	DPRINTFN(4, ("usbd_set_report_async: len=%d\n", len));
    282 	if (ifd == NULL)
    283 		return (USBD_IOERROR);
    284 	usbd_interface2device_handle(iface, &dev);
    285 	req.bmRequestType = UT_WRITE_CLASS_INTERFACE;
    286 	req.bRequest = UR_SET_REPORT;
    287 	USETW2(req.wValue, type, id);
    288 	USETW(req.wIndex, ifd->bInterfaceNumber);
    289 	USETW(req.wLength, len);
    290 	return (usbd_do_request_async(dev, &req, data));
    291 }
    292 
    293 usbd_status
    294 usbd_get_report(usbd_interface_handle iface, int type, int id, void *data,
    295 		int len)
    296 {
    297 	usb_interface_descriptor_t *ifd = usbd_get_interface_descriptor(iface);
    298 	usbd_device_handle dev;
    299 	usb_device_request_t req;
    300 
    301 	DPRINTFN(4, ("usbd_get_report: len=%d\n", len));
    302 	if (ifd == NULL)
    303 		return (USBD_IOERROR);
    304 	usbd_interface2device_handle(iface, &dev);
    305 	req.bmRequestType = UT_READ_CLASS_INTERFACE;
    306 	req.bRequest = UR_GET_REPORT;
    307 	USETW2(req.wValue, type, id);
    308 	USETW(req.wIndex, ifd->bInterfaceNumber);
    309 	USETW(req.wLength, len);
    310 	return (usbd_do_request(dev, &req, data));
    311 }
    312 
    313 usbd_status
    314 usbd_set_idle(usbd_interface_handle iface, int duration, int id)
    315 {
    316 	usb_interface_descriptor_t *ifd = usbd_get_interface_descriptor(iface);
    317 	usbd_device_handle dev;
    318 	usb_device_request_t req;
    319 
    320 	DPRINTFN(4, ("usbd_set_idle: %d %d\n", duration, id));
    321 	if (ifd == NULL)
    322 		return (USBD_IOERROR);
    323 	usbd_interface2device_handle(iface, &dev);
    324 	req.bmRequestType = UT_WRITE_CLASS_INTERFACE;
    325 	req.bRequest = UR_SET_IDLE;
    326 	USETW2(req.wValue, duration, id);
    327 	USETW(req.wIndex, ifd->bInterfaceNumber);
    328 	USETW(req.wLength, 0);
    329 	return (usbd_do_request(dev, &req, 0));
    330 }
    331 
    332 usbd_status
    333 usbd_get_report_descriptor(usbd_device_handle dev, int ifcno,
    334 			   int size, void *d)
    335 {
    336 	usb_device_request_t req;
    337 
    338 	req.bmRequestType = UT_READ_INTERFACE;
    339 	req.bRequest = UR_GET_DESCRIPTOR;
    340 	USETW2(req.wValue, UDESC_REPORT, 0); /* report id should be 0 */
    341 	USETW(req.wIndex, ifcno);
    342 	USETW(req.wLength, size);
    343 	return (usbd_do_request(dev, &req, d));
    344 }
    345 
    346 usb_hid_descriptor_t *
    347 usbd_get_hid_descriptor(usbd_interface_handle ifc)
    348 {
    349 	usb_interface_descriptor_t *idesc = usbd_get_interface_descriptor(ifc);
    350 	usbd_device_handle dev;
    351 	usb_config_descriptor_t *cdesc;
    352 	usb_hid_descriptor_t *hd;
    353 	char *p, *end;
    354 
    355 	if (idesc == NULL)
    356 		return (NULL);
    357 	usbd_interface2device_handle(ifc, &dev);
    358 	cdesc = usbd_get_config_descriptor(dev);
    359 
    360 	p = (char *)idesc + idesc->bLength;
    361 	end = (char *)cdesc + UGETW(cdesc->wTotalLength);
    362 
    363 	for (; p < end; p += hd->bLength) {
    364 		hd = (usb_hid_descriptor_t *)p;
    365 		if (p + hd->bLength <= end && hd->bDescriptorType == UDESC_HID)
    366 			return (hd);
    367 		if (hd->bDescriptorType == UDESC_INTERFACE)
    368 			break;
    369 	}
    370 	return (NULL);
    371 }
    372 
    373 usbd_status
    374 usbd_read_report_desc(usbd_interface_handle ifc, void **descp, int *sizep,
    375 		       struct malloc_type * mem)
    376 {
    377 	usb_interface_descriptor_t *id;
    378 	usb_hid_descriptor_t *hid;
    379 	usbd_device_handle dev;
    380 	usbd_status err;
    381 
    382 	usbd_interface2device_handle(ifc, &dev);
    383 	id = usbd_get_interface_descriptor(ifc);
    384 	if (id == NULL)
    385 		return (USBD_INVAL);
    386 	hid = usbd_get_hid_descriptor(ifc);
    387 	if (hid == NULL)
    388 		return (USBD_IOERROR);
    389 	*sizep = UGETW(hid->descrs[0].wDescriptorLength);
    390 	*descp = malloc(*sizep, mem, M_NOWAIT);
    391 	if (*descp == NULL)
    392 		return (USBD_NOMEM);
    393 	err = usbd_get_report_descriptor(dev, id->bInterfaceNumber,
    394 					 *sizep, *descp);
    395 	if (err) {
    396 		free(*descp, mem);
    397 		*descp = NULL;
    398 		return (err);
    399 	}
    400 	return (USBD_NORMAL_COMPLETION);
    401 }
    402 
    403 usbd_status
    404 usbd_get_config(usbd_device_handle dev, u_int8_t *conf)
    405 {
    406 	usb_device_request_t req;
    407 
    408 	req.bmRequestType = UT_READ_DEVICE;
    409 	req.bRequest = UR_GET_CONFIG;
    410 	USETW(req.wValue, 0);
    411 	USETW(req.wIndex, 0);
    412 	USETW(req.wLength, 1);
    413 	return (usbd_do_request(dev, &req, conf));
    414 }
    415 
    416 Static void usbd_bulk_transfer_cb(usbd_xfer_handle xfer,
    417 				  usbd_private_handle priv, usbd_status status);
    418 Static void
    419 usbd_bulk_transfer_cb(usbd_xfer_handle xfer, usbd_private_handle priv,
    420 		      usbd_status status)
    421 {
    422 	wakeup(xfer);
    423 }
    424 
    425 usbd_status
    426 usbd_bulk_transfer(usbd_xfer_handle xfer, usbd_pipe_handle pipe,
    427 		   u_int16_t flags, u_int32_t timeout, void *buf,
    428 		   u_int32_t *size, const char *lbl)
    429 {
    430 	usbd_status err;
    431 	int s, error;
    432 
    433 	usbd_setup_xfer(xfer, pipe, 0, buf, *size,
    434 			flags, timeout, usbd_bulk_transfer_cb);
    435 	DPRINTFN(1, ("usbd_bulk_transfer: start transfer %d bytes\n", *size));
    436 	s = splusb();		/* don't want callback until tsleep() */
    437 	err = usbd_transfer(xfer);
    438 	if (err != USBD_IN_PROGRESS) {
    439 		splx(s);
    440 		return (err);
    441 	}
    442 	error = tsleep(xfer, PZERO | PCATCH, lbl, 0);
    443 	splx(s);
    444 	if (error) {
    445 		DPRINTF(("usbd_bulk_transfer: tsleep=%d\n", error));
    446 		usbd_abort_pipe(pipe);
    447 		return (USBD_INTERRUPTED);
    448 	}
    449 	usbd_get_xfer_status(xfer, NULL, NULL, size, &err);
    450 	DPRINTFN(1,("usbd_bulk_transfer: transferred %d\n", *size));
    451 	if (err) {
    452 		DPRINTF(("usbd_bulk_transfer: error=%d\n", err));
    453 		usbd_clear_endpoint_stall(pipe);
    454 	}
    455 	return (err);
    456 }
    457 
    458 Static void usbd_intr_transfer_cb(usbd_xfer_handle xfer,
    459 				  usbd_private_handle priv, usbd_status status);
    460 Static void
    461 usbd_intr_transfer_cb(usbd_xfer_handle xfer, usbd_private_handle priv,
    462 		      usbd_status status)
    463 {
    464 	wakeup(xfer);
    465 }
    466 
    467 usbd_status
    468 usbd_intr_transfer(usbd_xfer_handle xfer, usbd_pipe_handle pipe,
    469 		   u_int16_t flags, u_int32_t timeout, void *buf,
    470 		   u_int32_t *size, const char *lbl)
    471 {
    472 	usbd_status err;
    473 	int s, error;
    474 
    475 	usbd_setup_xfer(xfer, pipe, 0, buf, *size,
    476 			flags, timeout, usbd_intr_transfer_cb);
    477 	DPRINTFN(1, ("usbd_intr_transfer: start transfer %d bytes\n", *size));
    478 	s = splusb();		/* don't want callback until tsleep() */
    479 	err = usbd_transfer(xfer);
    480 	if (err != USBD_IN_PROGRESS) {
    481 		splx(s);
    482 		return (err);
    483 	}
    484 	error = tsleep(xfer, PZERO | PCATCH, lbl, 0);
    485 	splx(s);
    486 	if (error) {
    487 		DPRINTF(("usbd_intr_transfer: tsleep=%d\n", error));
    488 		usbd_abort_pipe(pipe);
    489 		return (USBD_INTERRUPTED);
    490 	}
    491 	usbd_get_xfer_status(xfer, NULL, NULL, size, &err);
    492 	DPRINTFN(1,("usbd_intr_transfer: transferred %d\n", *size));
    493 	if (err) {
    494 		DPRINTF(("usbd_intr_transfer: error=%d\n", err));
    495 		usbd_clear_endpoint_stall(pipe);
    496 	}
    497 	return (err);
    498 }
    499 
    500 void
    501 usb_detach_waitold(device_t dv)
    502 {
    503 	DPRINTF(("usb_detach_waitold: waiting for %s\n", device_xname(dv)));
    504 	if (tsleep(dv, PZERO, "usbdet", hz * 60))
    505 		printf("usb_detach_waitold: %s didn't detach\n",
    506 		        device_xname(dv));
    507 	DPRINTF(("usb_detach_waitold: %s done\n", device_xname(dv)));
    508 }
    509 
    510 void
    511 usb_detach_wakeupold(device_t dv)
    512 {
    513 	DPRINTF(("usb_detach_wakeupold: for %s\n", device_xname(dv)));
    514 	wakeup(dv);
    515 }
    516 
    517 const usb_cdc_descriptor_t *
    518 usb_find_desc(usbd_device_handle dev, int type, int subtype)
    519 {
    520 	usbd_desc_iter_t iter;
    521 	const usb_cdc_descriptor_t *desc;
    522 
    523 	usb_desc_iter_init(dev, &iter);
    524 	for (;;) {
    525 		desc = (const usb_cdc_descriptor_t *)usb_desc_iter_next(&iter);
    526 		if (!desc || (desc->bDescriptorType == type &&
    527 			      (subtype == USBD_CDCSUBTYPE_ANY ||
    528 			       subtype == desc->bDescriptorSubtype)))
    529 			break;
    530 	}
    531 	return desc;
    532 }
    533 
    534 /* same as usb_find_desc(), but searches only in the specified interface. */
    535 const usb_cdc_descriptor_t *
    536 usb_find_desc_if(usbd_device_handle dev, int type, int subtype,
    537 		 usb_interface_descriptor_t *id)
    538 {
    539 	usbd_desc_iter_t iter;
    540 	const usb_cdc_descriptor_t *desc;
    541 
    542 	if (id == NULL)
    543 		return usb_find_desc(dev, type, subtype);
    544 
    545 	usb_desc_iter_init(dev, &iter);
    546 
    547 	iter.cur = (void *)id;		/* start from the interface desc */
    548 	usb_desc_iter_next(&iter);	/* and skip it */
    549 
    550 	while ((desc = (const usb_cdc_descriptor_t *)usb_desc_iter_next(&iter))
    551 	       != NULL) {
    552 		if (desc->bDescriptorType == UDESC_INTERFACE) {
    553 			/* we ran into the next interface --- not found */
    554 			return NULL;
    555 		}
    556 		if (desc->bDescriptorType == type &&
    557 		    (subtype == USBD_CDCSUBTYPE_ANY ||
    558 		     subtype == desc->bDescriptorSubtype))
    559 			break;
    560 	}
    561 	return desc;
    562 }
    563