/*=====================================================================================================*/
static int usb_get_string(struct usb_device *dev, unsigned short langid, unsigned char index, void *buf, int size)
{int i;
 int result;
 unsigned int pipe;
 pipe= usb_rcvctrlpipe(dev, 0);
 for (i = 0; i < 3; ++i)
	{/* retry on length 0 or stall; some devices are flakey */
	 result = usb_control_msg(dev, pipe, USB_REQ_GET_DESCRIPTOR, USB_DIR_IN, (USB_DT_STRING << 8) + index, langid, buf, size);
	 if (!(result == 0 || result == -EPIPE))
		break;
	}
 return result;
}
/*=====================================================================================================*/
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] < rc)
		rc = buf[0];
	 rc = rc - (rc & 1); /* force a multiple of two */
	}
 if (rc < 2)
	rc = (rc < 0)? rc : -EINVAL;
 return rc;
}
/*=====================================================================================================*/
/*	returns string length (> 0) or error (< 0) */
static int usb_string(struct usb_device *dev, int index, char *buf, size_t size)
{int r;
 unsigned int u, idx;
 unsigned char *str;
 str= (unsigned char *)usb_buf_1;
 if (size <= 0 || !buf || !index)
	return -EINVAL;
 buf[0] = 0;
 /* get langid for strings if it's not yet known */
 if (!dev->have_langid)
	{if( (r = usb_string_sub(dev, 0, 0, str)) < 0)
		{diag_printf ("ошибка чтения дескриптора строки: %d.\n",	r); return r;}
	 if(r < 4)																/* if(r >=0) r == strlen(usb_sting) */
		{diag_printf ("ошибка: неполный дескриптор строки.\n"); return -EINVAL;}
	 dev->have_langid = -1;
	 dev->string_langid = str[2] | (str[3]<< 8);
	/* always use the first langid listed */
#ifdef USB_DEBUG
	 diag_printf ("default language= 0x%04x\n", dev->string_langid);
#endif
	}
 r = usb_string_sub(dev, dev->string_langid, index, str);
 if(r < 0)
	{return r;}
 size--;																	/* leave room for trailing NULL char in output buffer */
 for(idx = 0, u = 2; u < r; u += 2)
	{if (idx >= size)
		break;
	 if (str[u+1])														/* high byte */
		buf[idx++] = '?';  													/* non ISO-8859-1 character */
	 else
		buf[idx++] = str[u];
	}
 buf[idx] = 0;
 r = idx;
 if(str[1] != USB_DT_STRING)
	diag_printf("ошибочный тип дескриптора %02x для строки %d (\"%s\")\n", str[1], index, buf);
#ifdef USB_DEBUG
 diag_printf("%s> [%s] r=%d \n", __FUNCTION__, buf, r);
#endif
 return r;
}