X-Git-Url: http://git.linex4red.de/pub/USBasp.git/blobdiff_plain/1e1cf2c499d7ac0cfae536e1264af4645350813b..6122ba93cf957bd495fdd1838bac16fb24896a17:/Demos/Device/ClassDriver/MassStorageKeyboard/Descriptors.c

diff --git a/Demos/Device/ClassDriver/MassStorageKeyboard/Descriptors.c b/Demos/Device/ClassDriver/MassStorageKeyboard/Descriptors.c
index b779ea342..d3e4214fa 100644
--- a/Demos/Device/ClassDriver/MassStorageKeyboard/Descriptors.c
+++ b/Demos/Device/ClassDriver/MassStorageKeyboard/Descriptors.c
@@ -29,10 +29,6 @@
   this software.
 */
 
-#if (USE_INTERNAL_SERIAL == NO_DESCRIPTOR)
-	#warning USE_INTERNAL_SERIAL is not available on this AVR - please manually construct a device serial descriptor.
-#endif
-
 /** \file
  *
  *  USB Device Descriptors, for library use when in USB device mode. Descriptors are special 
@@ -42,6 +38,18 @@
 
 #include "Descriptors.h"
 
+/* On some devices, there is a factory set internal serial number which can be automatically sent to the host as
+ * the device's serial number when the Device Descriptor's .SerialNumStrIndex entry is set to USE_INTERNAL_SERIAL.
+ * This allows the host to track a device across insertions on different ports, allowing them to retain allocated
+ * resources like COM port numbers and drivers. On demos using this feature, give a warning on unsupported devices
+ * so that the user can supply their own serial number descriptor instead or remove the USE_INTERNAL_SERIAL value
+ * from the Device Descriptor (forcing the host to generate a serial number for each device from the VID, PID and
+ * port location).
+ */
+#if (USE_INTERNAL_SERIAL == NO_DESCRIPTOR)
+	#warning USE_INTERNAL_SERIAL is not available on this AVR - please manually construct a device serial descriptor.
+#endif
+
 /** HID class report descriptor. This is a special descriptor constructed with values from the
  *  USBIF HID class specification to describe the reports and capabilities of the HID device. This
  *  descriptor is parsed by the host and its contents used to determine what data (and in what encoding)