- return usb_control_msg(dev, usb_rcvctrlpipe(dev, 0),
- USB_REQ_GET_DESCRIPTOR, USB_DIR_IN,
- (USB_DT_STRING << 8) + index, langid, buf, size, USB_CNTL_TIMEOUT);
+ int i;
+ int result;
+
+ for (i = 0; i < 3; ++i) {
+ /* some devices are flaky */
+ result = usb_control_msg(dev, usb_rcvctrlpipe(dev, 0),
+ USB_REQ_GET_DESCRIPTOR, USB_DIR_IN,
+ (USB_DT_STRING << 8) + index, langid, buf, size,
+ USB_CNTL_TIMEOUT);
+
+ if (result > 0)
+ break;
+ }
+
+ return result;
+}
+
+
+static void usb_try_string_workarounds(unsigned char *buf, int *length)
+{
+ int newlength, oldlength = *length;
+
+ for (newlength = 2; newlength + 1 < oldlength; newlength += 2)
+ if (!isprint(buf[newlength]) || buf[newlength + 1])
+ break;
+
+ if (newlength > 2) {
+ buf[0] = newlength;
+ *length = newlength;
+ }
+}
+
+
+static int usb_string_sub(struct usb_device *dev, unsigned int langid,
+ unsigned int index, unsigned char *buf)
+{
+ int rc;
+
+ /* Try to read the string descriptor by asking for the maximum
+ * possible number of bytes */
+ rc = usb_get_string(dev, langid, index, buf, 255);
+
+ /* If that failed try to read the descriptor length, then
+ * ask for just that many bytes */
+ if (rc < 2) {
+ rc = usb_get_string(dev, langid, index, buf, 2);
+ if (rc == 2)
+ rc = usb_get_string(dev, langid, index, buf, buf[0]);
+ }
+
+ if (rc >= 2) {
+ if (!buf[0] && !buf[1])
+ usb_try_string_workarounds(buf, &rc);
+
+ /* There might be extra junk at the end of the descriptor */
+ if (buf[0] < rc)
+ rc = buf[0];
+
+ rc = rc - (rc & 1); /* force a multiple of two */
+ }
+
+ if (rc < 2)
+ rc = -1;
+
+ return rc;