rt2x00: clarify meaning of txdone flags

Update the documentation of the available txdone flags to better express
how they should be used.

Signed-off-by: Helmut Schaa <helmut.schaa@googlemail.com>
Acked-by: Gertjan van Wingerde <gwingerde@gmail.com>
Signed-off-by: Ivo van Doorn <IvDoorn@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/rt2x00/rt2x00queue.h

@@ -213,9 +213,16 @@ struct rxdone_entry_desc {
 /**
  * enum txdone_entry_desc_flags: Flags for &struct txdone_entry_desc
  *
+ * Every txdone report has to contain the basic result of the
+ * transmission, either &TXDONE_UNKNOWN, &TXDONE_SUCCESS or
+ * &TXDONE_FAILURE. The flag &TXDONE_FALLBACK can be used in
+ * conjunction with all of these flags but should only be set
+ * if retires > 0. The flag &TXDONE_EXCESSIVE_RETRY can only be used
+ * in conjunction with &TXDONE_FAILURE.
+ *
  * @TXDONE_UNKNOWN: Hardware could not determine success of transmission.
  * @TXDONE_SUCCESS: Frame was successfully send
- * @TXDONE_FALLBACK: Frame was successfully send using a fallback rate.
+ * @TXDONE_FALLBACK: Hardware used fallback rates for retries
  * @TXDONE_FAILURE: Frame was not successfully send
  * @TXDONE_EXCESSIVE_RETRY: In addition to &TXDONE_FAILURE, the
  *	frame transmission failed due to excessive retries.