+ util_strlcpy(to, type, len);
+}
+
+#define USB_DT_DEVICE 0x01
+#define USB_DT_INTERFACE 0x04
+
+static int dev_if_packed_info(struct udev_device *dev, char *ifs_str, size_t len)
+{
+ char *filename = NULL;
+ int fd;
+ ssize_t size;
+ unsigned char buf[18 + 65535];
+ unsigned int pos, strpos;
+ struct usb_interface_descriptor {
+ u_int8_t bLength;
+ u_int8_t bDescriptorType;
+ u_int8_t bInterfaceNumber;
+ u_int8_t bAlternateSetting;
+ u_int8_t bNumEndpoints;
+ u_int8_t bInterfaceClass;
+ u_int8_t bInterfaceSubClass;
+ u_int8_t bInterfaceProtocol;
+ u_int8_t iInterface;
+ } __attribute__((packed));
+ int err = 0;
+
+ if (asprintf(&filename, "%s/descriptors", udev_device_get_syspath(dev)) < 0) {
+ err = -1;
+ goto out;
+ }
+ fd = open(filename, O_RDONLY);
+ if (fd < 0) {
+ fprintf(stderr, "error opening USB device 'descriptors' file\n");
+ err = -1;
+ goto out;
+ }
+ size = read(fd, buf, sizeof(buf));
+ close(fd);
+ if (size < 18 || size == sizeof(buf)) {
+ err = -1;
+ goto out;
+ }
+
+ pos = 0;
+ strpos = 0;
+ while (pos < sizeof(buf) && strpos+7 < len) {
+ struct usb_interface_descriptor *desc;
+ char if_str[8];
+
+ desc = (struct usb_interface_descriptor *) &buf[pos];
+ if (desc->bLength < 3)
+ break;
+ pos += desc->bLength;
+
+ if (desc->bDescriptorType != USB_DT_INTERFACE)
+ continue;
+
+ if (snprintf(if_str, 8, "%02x%02x%02x:",
+ desc->bInterfaceClass,
+ desc->bInterfaceSubClass,
+ desc->bInterfaceProtocol) != 7)
+ continue;
+
+ if (strstr(ifs_str, if_str) != NULL)
+ continue;
+
+ memcpy(&ifs_str[strpos], if_str, 8),
+ strpos += 7;
+ }
+out:
+ free(filename);
+ return err;