diff --git a/src/core/errno.c b/src/core/errno.c
index e72acdd0..83c8564b 100644
--- a/src/core/errno.c
+++ b/src/core/errno.c
@@ -6,7 +6,18 @@
  *
  * Error codes and descriptions.
  *
- * This file provides the global variable errno
+ * This file provides the global variable #errno and the function
+ * strerror().  These function much like their standard C library
+ * equivalents.
+ *
+ * The error numbers used by Etherboot are a superset of those defined
+ * by the PXE specification version 2.1.  See errno.h for a listing of
+ * the error values.
+ *
+ * To save space in ROM images, error string tables are optional.  Use
+ * the ERRORMSG_XXX options in config.h to select which error string
+ * tables you want to include.  If an error string table is omitted,
+ * strerror() will simply return the text "Error 0x<errno>".
  *
  */
 
@@ -29,7 +40,7 @@ static struct errortab errortab_end[0] __table_end(errortab);
  * @ret strerror	Pointer to error text
  *
  * If the error is not found in the linked-in error tables, generates
- * a generic "Error 0x0000" message.
+ * a generic "Error 0x<errno>" message.
  *
  * The pointer returned by strerror() is valid only until the next
  * call to strerror().
diff --git a/src/include/errno.h b/src/include/errno.h
index a3c7fbbb..e122d9c3 100644
--- a/src/include/errno.h
+++ b/src/include/errno.h
@@ -1,11 +1,9 @@
 #ifndef ERRNO_H
 #define ERRNO_H
 
-/*
- * We define error codes that are a superset of those mentioned in the
- * PXE specification.  Various error string tables may be compiled in
- * if required; if not compiled in, strerror(errno) will produce the
- * text "error 0x<errno>".
+/** @file
+ *
+ * Error codes
  *
  */