Index: uspace/lib/c/generic/str_error.c
===================================================================
--- uspace/lib/c/generic/str_error.c	(revision 55f690cfe3642902c64342ac8b3dc594d12cef29)
+++ uspace/lib/c/generic/str_error.c	(revision b36e5de2b3fb91be80216fe929bf2bfee1268933)
@@ -73,4 +73,6 @@
 		case EBADCHECKSUM:
 			return "Bad checksum";
+		case ESTALL:
+			return "Operation stalled";
 		case EAGAIN:
 			return "Resource temporarily unavailable";
Index: uspace/lib/c/include/errno.h
===================================================================
--- uspace/lib/c/include/errno.h	(revision 55f690cfe3642902c64342ac8b3dc594d12cef29)
+++ uspace/lib/c/include/errno.h	(revision b36e5de2b3fb91be80216fe929bf2bfee1268933)
@@ -59,4 +59,7 @@
 #define EBADCHECKSUM  (-300)
 
+/** USB: stalled operation. */
+#define ESTALL (-301)
+
 /** An API function is called while another blocking function is in progress. */
 #define EINPROGRESS  (-10036)