Index: uspace/lib/usb/include/usb/descriptor.h
===================================================================
--- uspace/lib/usb/include/usb/descriptor.h	(revision 82a639cd0a9e74f1cfd6371a5b3320f9e899f857)
+++ uspace/lib/usb/include/usb/descriptor.h	(revision ce735cc2430e8f0bfa1d2e2c249371c607b68bfb)
@@ -197,6 +197,14 @@
 	 */
 	uint8_t attributes;
-	/** Maximum packet size. */
+	/** Maximum packet size.
+	 * Lower 10 bits represent the actuall size
+	 * Bits 11,12 specify addtional transfer opportunitities for
+	 * HS INT and ISO transfers. */
 	uint16_t max_packet_size;
+#define ED_MPS_PACKET_SIZE_MASK  0x3ff
+#define ED_MPS_PACKET_SIZE_GET(value) \
+	((value) & ED_MPS_PACKET_SIZE_MASK)
+#define ED_MPS_TRANS_OPPORTUNITIES_GET(value) \
+	((((value) >> 10) & 0x3) + 1)
 	/** Polling interval in milliseconds.
 	 * Ignored for bulk and control endpoints.