improve host configuration parsing

- remove driver class code binding
- fully support IAD
- auto calculate total length for interface descriptor for driver

src/tusb.c

@@ -125,6 +125,36 @@ void tu_edpt_bind_driver(uint8_t ep2drv[][2], tusb_desc_interface_t const* desc_
   }
 }
 
+uint16_t tu_desc_get_interface_total_len(tusb_desc_interface_t const* desc_itf, uint8_t itf_count, uint16_t max_len)
+{
+  uint8_t const* p_desc = (uint8_t const*) desc_itf;
+  uint16_t len = 0;
+
+  while (itf_count--)
+  {
+    // Next on interface desc
+    len += tu_desc_len(desc_itf);
+    p_desc = tu_desc_next(p_desc);
+
+    while (len < max_len)
+    {
+      // return on IAD regardless of itf count
+      if ( tu_desc_type(p_desc) == TUSB_DESC_INTERFACE_ASSOCIATION ) return len;
+
+      if ( (tu_desc_type(p_desc) == TUSB_DESC_INTERFACE) &&
+           ((tusb_desc_interface_t const*) p_desc)->bAlternateSetting == 0 )
+      {
+        break;
+      }
+
+      len += tu_desc_len(p_desc);
+      p_desc = tu_desc_next(p_desc);
+    }
+  }
+
+  return len;
+}
+
 /*------------------------------------------------------------------*/
 /* Debug
  *------------------------------------------------------------------*/