2 * USB descriptor handling functions for libusbx
3 * Copyright © 2007 Daniel Drake <dsd@gentoo.org>
4 * Copyright © 2001 Johannes Erdfelt <johannes@erdfelt.com>
6 * This library is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU Lesser General Public
8 * License as published by the Free Software Foundation; either
9 * version 2.1 of the License, or (at your option) any later version.
11 * This library is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 * Lesser General Public License for more details.
16 * You should have received a copy of the GNU Lesser General Public
17 * License along with this library; if not, write to the Free Software
18 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
28 #define DESC_HEADER_LENGTH 2
29 #define DEVICE_DESC_LENGTH 18
30 #define CONFIG_DESC_LENGTH 9
31 #define INTERFACE_DESC_LENGTH 9
32 #define ENDPOINT_DESC_LENGTH 7
33 #define ENDPOINT_AUDIO_DESC_LENGTH 9
35 /** @defgroup desc USB descriptors
36 * This page details how to examine the various standard USB descriptors
37 * for detected devices
40 /* set host_endian if the w values are already in host endian format,
41 * as opposed to bus endian. */
42 int usbi_parse_descriptor(unsigned char *source, const char *descriptor,
43 void *dest, int host_endian)
45 unsigned char *sp = source, *dp = dest;
49 for (cp = descriptor; *cp; cp++) {
51 case 'b': /* 8-bit byte */
54 case 'w': /* 16-bit word, convert from little endian to CPU */
55 dp += ((uintptr_t)dp & 1); /* Align to word boundary */
60 w = (sp[1] << 8) | sp[0];
61 *((uint16_t *)dp) = w;
69 return (int) (sp - source);
72 static void clear_endpoint(struct libusb_endpoint_descriptor *endpoint)
75 free((unsigned char *) endpoint->extra);
78 static int parse_endpoint(struct libusb_context *ctx,
79 struct libusb_endpoint_descriptor *endpoint, unsigned char *buffer,
80 int size, int host_endian)
82 struct usb_descriptor_header header;
88 usbi_parse_descriptor(buffer, "bb", &header, 0);
90 /* Everything should be fine being passed into here, but we sanity */
92 if (header.bLength > size) {
93 usbi_err(ctx, "ran out of descriptors parsing");
97 if (header.bDescriptorType != LIBUSB_DT_ENDPOINT) {
98 usbi_err(ctx, "unexpected descriptor %x (expected %x)",
99 header.bDescriptorType, LIBUSB_DT_ENDPOINT);
103 if (header.bLength >= ENDPOINT_AUDIO_DESC_LENGTH)
104 usbi_parse_descriptor(buffer, "bbbbwbbb", endpoint, host_endian);
105 else if (header.bLength >= ENDPOINT_DESC_LENGTH)
106 usbi_parse_descriptor(buffer, "bbbbwb", endpoint, host_endian);
108 buffer += header.bLength;
109 size -= header.bLength;
110 parsed += header.bLength;
112 /* Skip over the rest of the Class Specific or Vendor Specific */
115 while (size >= DESC_HEADER_LENGTH) {
116 usbi_parse_descriptor(buffer, "bb", &header, 0);
118 if (header.bLength < 2) {
119 usbi_err(ctx, "invalid descriptor length %d", header.bLength);
123 /* If we find another "proper" descriptor then we're done */
124 if ((header.bDescriptorType == LIBUSB_DT_ENDPOINT) ||
125 (header.bDescriptorType == LIBUSB_DT_INTERFACE) ||
126 (header.bDescriptorType == LIBUSB_DT_CONFIG) ||
127 (header.bDescriptorType == LIBUSB_DT_DEVICE))
130 usbi_dbg("skipping descriptor %x", header.bDescriptorType);
131 buffer += header.bLength;
132 size -= header.bLength;
133 parsed += header.bLength;
136 /* Copy any unknown descriptors into a storage area for drivers */
138 len = (int)(buffer - begin);
140 endpoint->extra = NULL;
141 endpoint->extra_length = 0;
146 endpoint->extra = extra;
148 endpoint->extra_length = 0;
149 return LIBUSB_ERROR_NO_MEM;
152 memcpy(extra, begin, len);
153 endpoint->extra_length = len;
158 static void clear_interface(struct libusb_interface *usb_interface)
163 if (usb_interface->altsetting) {
164 for (i = 0; i < usb_interface->num_altsetting; i++) {
165 struct libusb_interface_descriptor *ifp =
166 (struct libusb_interface_descriptor *)
167 usb_interface->altsetting + i;
169 free((void *) ifp->extra);
171 for (j = 0; j < ifp->bNumEndpoints; j++)
172 clear_endpoint((struct libusb_endpoint_descriptor *)
174 free((void *) ifp->endpoint);
177 free((void *) usb_interface->altsetting);
178 usb_interface->altsetting = NULL;
183 static int parse_interface(libusb_context *ctx,
184 struct libusb_interface *usb_interface, unsigned char *buffer, int size,
192 struct usb_descriptor_header header;
193 struct libusb_interface_descriptor *ifp;
194 unsigned char *begin;
196 usb_interface->num_altsetting = 0;
198 while (size >= INTERFACE_DESC_LENGTH) {
199 struct libusb_interface_descriptor *altsetting =
200 (struct libusb_interface_descriptor *) usb_interface->altsetting;
201 altsetting = usbi_reallocf(altsetting,
202 sizeof(struct libusb_interface_descriptor) *
203 (usb_interface->num_altsetting + 1));
205 r = LIBUSB_ERROR_NO_MEM;
208 usb_interface->altsetting = altsetting;
210 ifp = altsetting + usb_interface->num_altsetting;
211 usb_interface->num_altsetting++;
212 usbi_parse_descriptor(buffer, "bbbbbbbbb", ifp, 0);
214 ifp->extra_length = 0;
215 ifp->endpoint = NULL;
217 /* Skip over the interface */
218 buffer += ifp->bLength;
219 parsed += ifp->bLength;
220 size -= ifp->bLength;
224 /* Skip over any interface, class or vendor descriptors */
225 while (size >= DESC_HEADER_LENGTH) {
226 usbi_parse_descriptor(buffer, "bb", &header, 0);
227 if (header.bLength < 2) {
228 usbi_err(ctx, "invalid descriptor of length %d",
234 /* If we find another "proper" descriptor then we're done */
235 if ((header.bDescriptorType == LIBUSB_DT_INTERFACE) ||
236 (header.bDescriptorType == LIBUSB_DT_ENDPOINT) ||
237 (header.bDescriptorType == LIBUSB_DT_CONFIG) ||
238 (header.bDescriptorType == LIBUSB_DT_DEVICE))
241 buffer += header.bLength;
242 parsed += header.bLength;
243 size -= header.bLength;
246 /* Copy any unknown descriptors into a storage area for */
247 /* drivers to later parse */
248 len = (int)(buffer - begin);
250 ifp->extra = malloc(len);
252 r = LIBUSB_ERROR_NO_MEM;
255 memcpy((unsigned char *) ifp->extra, begin, len);
256 ifp->extra_length = len;
259 /* Did we hit an unexpected descriptor? */
260 if (size >= DESC_HEADER_LENGTH) {
261 usbi_parse_descriptor(buffer, "bb", &header, 0);
262 if ((header.bDescriptorType == LIBUSB_DT_CONFIG) ||
263 (header.bDescriptorType == LIBUSB_DT_DEVICE)) {
268 if (ifp->bNumEndpoints > USB_MAXENDPOINTS) {
269 usbi_err(ctx, "too many endpoints (%d)", ifp->bNumEndpoints);
274 if (ifp->bNumEndpoints > 0) {
275 struct libusb_endpoint_descriptor *endpoint;
276 tmp = ifp->bNumEndpoints * sizeof(struct libusb_endpoint_descriptor);
277 endpoint = malloc(tmp);
278 ifp->endpoint = endpoint;
280 r = LIBUSB_ERROR_NO_MEM;
284 memset(endpoint, 0, tmp);
285 for (i = 0; i < ifp->bNumEndpoints; i++) {
286 usbi_parse_descriptor(buffer, "bb", &header, 0);
288 if (header.bLength > size) {
289 usbi_err(ctx, "ran out of descriptors parsing");
294 r = parse_endpoint(ctx, endpoint + i, buffer, size,
305 /* We check to see if it's an alternate to this one */
306 ifp = (struct libusb_interface_descriptor *) buffer;
307 if (size < LIBUSB_DT_INTERFACE_SIZE ||
308 ifp->bDescriptorType != LIBUSB_DT_INTERFACE ||
309 !ifp->bAlternateSetting)
315 clear_interface(usb_interface);
319 static void clear_configuration(struct libusb_config_descriptor *config)
321 if (config->interface) {
323 for (i = 0; i < config->bNumInterfaces; i++)
324 clear_interface((struct libusb_interface *)
325 config->interface + i);
326 free((void *) config->interface);
329 free((void *) config->extra);
332 static int parse_configuration(struct libusb_context *ctx,
333 struct libusb_config_descriptor *config, unsigned char *buffer,
340 struct usb_descriptor_header header;
341 struct libusb_interface *usb_interface;
343 usbi_parse_descriptor(buffer, "bbwbbbbb", config, host_endian);
344 size = config->wTotalLength;
346 if (config->bNumInterfaces > USB_MAXINTERFACES) {
347 usbi_err(ctx, "too many interfaces (%d)", config->bNumInterfaces);
348 return LIBUSB_ERROR_IO;
351 tmp = config->bNumInterfaces * sizeof(struct libusb_interface);
352 usb_interface = malloc(tmp);
353 config->interface = usb_interface;
354 if (!config->interface)
355 return LIBUSB_ERROR_NO_MEM;
357 memset(usb_interface, 0, tmp);
358 buffer += config->bLength;
359 size -= config->bLength;
361 config->extra = NULL;
362 config->extra_length = 0;
364 for (i = 0; i < config->bNumInterfaces; i++) {
366 unsigned char *begin;
368 /* Skip over the rest of the Class Specific or Vendor */
369 /* Specific descriptors */
371 while (size >= DESC_HEADER_LENGTH) {
372 usbi_parse_descriptor(buffer, "bb", &header, 0);
374 if ((header.bLength > size) ||
375 (header.bLength < DESC_HEADER_LENGTH)) {
376 usbi_err(ctx, "invalid descriptor length of %d",
382 /* If we find another "proper" descriptor then we're done */
383 if ((header.bDescriptorType == LIBUSB_DT_ENDPOINT) ||
384 (header.bDescriptorType == LIBUSB_DT_INTERFACE) ||
385 (header.bDescriptorType == LIBUSB_DT_CONFIG) ||
386 (header.bDescriptorType == LIBUSB_DT_DEVICE))
389 usbi_dbg("skipping descriptor 0x%x\n", header.bDescriptorType);
390 buffer += header.bLength;
391 size -= header.bLength;
394 /* Copy any unknown descriptors into a storage area for */
395 /* drivers to later parse */
396 len = (int)(buffer - begin);
398 /* FIXME: We should realloc and append here */
399 if (!config->extra_length) {
400 config->extra = malloc(len);
401 if (!config->extra) {
402 r = LIBUSB_ERROR_NO_MEM;
406 memcpy((unsigned char *) config->extra, begin, len);
407 config->extra_length = len;
411 r = parse_interface(ctx, usb_interface + i, buffer, size, host_endian);
422 clear_configuration(config);
427 * Get the USB device descriptor for a given device.
429 * This is a non-blocking function; the device descriptor is cached in memory.
431 * \param dev the device
432 * \param desc output location for the descriptor data
433 * \returns 0 on success or a LIBUSB_ERROR code on failure
435 int API_EXPORTED libusb_get_device_descriptor(libusb_device *dev,
436 struct libusb_device_descriptor *desc)
438 unsigned char raw_desc[DEVICE_DESC_LENGTH];
443 r = usbi_backend->get_device_descriptor(dev, raw_desc, &host_endian);
447 memcpy((unsigned char *) desc, raw_desc, sizeof(raw_desc));
449 desc->bcdUSB = libusb_le16_to_cpu(desc->bcdUSB);
450 desc->idVendor = libusb_le16_to_cpu(desc->idVendor);
451 desc->idProduct = libusb_le16_to_cpu(desc->idProduct);
452 desc->bcdDevice = libusb_le16_to_cpu(desc->bcdDevice);
458 * Get the USB configuration descriptor for the currently active configuration.
459 * This is a non-blocking function which does not involve any requests being
460 * sent to the device.
462 * \param dev a device
463 * \param config output location for the USB configuration descriptor. Only
464 * valid if 0 was returned. Must be freed with libusb_free_config_descriptor()
466 * \returns 0 on success
467 * \returns LIBUSB_ERROR_NOT_FOUND if the device is in unconfigured state
468 * \returns another LIBUSB_ERROR code on error
469 * \see libusb_get_config_descriptor
471 int API_EXPORTED libusb_get_active_config_descriptor(libusb_device *dev,
472 struct libusb_config_descriptor **config)
474 struct libusb_config_descriptor *_config = malloc(sizeof(*_config));
475 unsigned char tmp[8];
476 unsigned char *buf = NULL;
482 return LIBUSB_ERROR_NO_MEM;
484 r = usbi_backend->get_active_config_descriptor(dev, tmp, sizeof(tmp),
489 _config->wTotalLength = 0;
490 usbi_parse_descriptor(tmp, "bbw", _config, host_endian);
491 if (_config->wTotalLength != 0)
492 buf = malloc(_config->wTotalLength);
494 r = LIBUSB_ERROR_NO_MEM;
498 r = usbi_backend->get_active_config_descriptor(dev, buf,
499 _config->wTotalLength, &host_endian);
503 r = parse_configuration(dev->ctx, _config, buf, host_endian);
505 usbi_err(dev->ctx, "parse_configuration failed with error %d", r);
508 usbi_warn(dev->ctx, "descriptor data still left");
523 * Get a USB configuration descriptor based on its index.
524 * This is a non-blocking function which does not involve any requests being
525 * sent to the device.
527 * \param dev a device
528 * \param config_index the index of the configuration you wish to retrieve
529 * \param config output location for the USB configuration descriptor. Only
530 * valid if 0 was returned. Must be freed with libusb_free_config_descriptor()
532 * \returns 0 on success
533 * \returns LIBUSB_ERROR_NOT_FOUND if the configuration does not exist
534 * \returns another LIBUSB_ERROR code on error
535 * \see libusb_get_active_config_descriptor()
536 * \see libusb_get_config_descriptor_by_value()
538 int API_EXPORTED libusb_get_config_descriptor(libusb_device *dev,
539 uint8_t config_index, struct libusb_config_descriptor **config)
541 struct libusb_config_descriptor *_config;
542 unsigned char tmp[8];
543 unsigned char *buf = NULL;
547 usbi_dbg("index %d", config_index);
548 if (config_index >= dev->num_configurations)
549 return LIBUSB_ERROR_NOT_FOUND;
551 _config = malloc(sizeof(*_config));
553 return LIBUSB_ERROR_NO_MEM;
555 r = usbi_backend->get_config_descriptor(dev, config_index, tmp,
556 sizeof(tmp), &host_endian);
560 usbi_parse_descriptor(tmp, "bbw", _config, host_endian);
561 buf = malloc(_config->wTotalLength);
563 r = LIBUSB_ERROR_NO_MEM;
568 r = usbi_backend->get_config_descriptor(dev, config_index, buf,
569 _config->wTotalLength, &host_endian);
573 r = parse_configuration(dev->ctx, _config, buf, host_endian);
575 usbi_err(dev->ctx, "parse_configuration failed with error %d", r);
578 usbi_warn(dev->ctx, "descriptor data still left");
592 /* iterate through all configurations, returning the index of the configuration
593 * matching a specific bConfigurationValue in the idx output parameter, or -1
594 * if the config was not found.
595 * returns 0 or a LIBUSB_ERROR code
597 int usbi_get_config_index_by_value(struct libusb_device *dev,
598 uint8_t bConfigurationValue, int *idx)
602 usbi_dbg("value %d", bConfigurationValue);
603 for (i = 0; i < dev->num_configurations; i++) {
604 unsigned char tmp[6];
606 int r = usbi_backend->get_config_descriptor(dev, i, tmp, sizeof(tmp),
610 if (tmp[5] == bConfigurationValue) {
621 * Get a USB configuration descriptor with a specific bConfigurationValue.
622 * This is a non-blocking function which does not involve any requests being
623 * sent to the device.
625 * \param dev a device
626 * \param bConfigurationValue the bConfigurationValue of the configuration you
628 * \param config output location for the USB configuration descriptor. Only
629 * valid if 0 was returned. Must be freed with libusb_free_config_descriptor()
631 * \returns 0 on success
632 * \returns LIBUSB_ERROR_NOT_FOUND if the configuration does not exist
633 * \returns another LIBUSB_ERROR code on error
634 * \see libusb_get_active_config_descriptor()
635 * \see libusb_get_config_descriptor()
637 int API_EXPORTED libusb_get_config_descriptor_by_value(libusb_device *dev,
638 uint8_t bConfigurationValue, struct libusb_config_descriptor **config)
641 int r = usbi_get_config_index_by_value(dev, bConfigurationValue, &idx);
645 return LIBUSB_ERROR_NOT_FOUND;
647 return libusb_get_config_descriptor(dev, (uint8_t) idx, config);
651 * Free a configuration descriptor obtained from
652 * libusb_get_active_config_descriptor() or libusb_get_config_descriptor().
653 * It is safe to call this function with a NULL config parameter, in which
654 * case the function simply returns.
656 * \param config the configuration descriptor to free
658 void API_EXPORTED libusb_free_config_descriptor(
659 struct libusb_config_descriptor *config)
664 clear_configuration(config);
669 * Retrieve a string descriptor in C style ASCII.
671 * Wrapper around libusb_get_string_descriptor(). Uses the first language
672 * supported by the device.
674 * \param dev a device handle
675 * \param desc_index the index of the descriptor to retrieve
676 * \param data output buffer for ASCII string descriptor
677 * \param length size of data buffer
678 * \returns number of bytes returned in data, or LIBUSB_ERROR code on failure
680 int API_EXPORTED libusb_get_string_descriptor_ascii(libusb_device_handle *dev,
681 uint8_t desc_index, unsigned char *data, int length)
683 unsigned char tbuf[255]; /* Some devices choke on size > 255 */
687 /* Asking for the zero'th index is special - it returns a string
688 * descriptor that contains all the language IDs supported by the
689 * device. Typically there aren't many - often only one. Language
690 * IDs are 16 bit numbers, and they start at the third byte in the
691 * descriptor. There's also no point in trying to read descriptor 0
692 * with this function. See USB 2.0 specification section 9.6.7 for
697 return LIBUSB_ERROR_INVALID_PARAM;
699 r = libusb_get_string_descriptor(dev, 0, 0, tbuf, sizeof(tbuf));
704 return LIBUSB_ERROR_IO;
706 langid = tbuf[2] | (tbuf[3] << 8);
708 r = libusb_get_string_descriptor(dev, desc_index, langid, tbuf,
713 if (tbuf[1] != LIBUSB_DT_STRING)
714 return LIBUSB_ERROR_IO;
717 return LIBUSB_ERROR_IO;
719 for (di = 0, si = 2; si < tbuf[0]; si += 2) {
720 if (di >= (length - 1))
723 if (tbuf[si + 1]) /* high byte */
726 data[di++] = tbuf[si];