diff --git a/include/uapi/linux/ethtool.h b/include/uapi/linux/ethtool.h
index 517b68c5fcec..f6ef7d42c7a1 100644
--- a/include/uapi/linux/ethtool.h
+++ b/include/uapi/linux/ethtool.h
@@ -1376,11 +1376,29 @@ struct ethtool_per_queue_op {
 };
 
 /**
- * struct ethtool_fecparam - Ethernet forward error correction(fec) parameters
+ * struct ethtool_fecparam - Ethernet Forward Error Correction parameters
  * @cmd: Command number = %ETHTOOL_GFECPARAM or %ETHTOOL_SFECPARAM
- * @active_fec: FEC mode which is active on the port, GET only.
- * @fec: Bitmask of supported/configured FEC modes
+ * @active_fec: FEC mode which is active on the port, single bit set, GET only.
+ * @fec: Bitmask of configured FEC modes.
  * @reserved: Reserved for future extensions, ignore on GET, write 0 for SET.
+ *
+ * FEC modes supported by the device can be read via %ETHTOOL_GLINKSETTINGS.
+ * FEC settings are configured by link autonegotiation whenever it's enabled.
+ * With autoneg on %ETHTOOL_GFECPARAM can be used to read the current mode.
+ *
+ * When autoneg is disabled %ETHTOOL_SFECPARAM controls the FEC settings.
+ * It is recommended that drivers only accept a single bit set in @fec.
+ * When multiple bits are set in @fec drivers may pick mode in an implementation
+ * dependent way. Drivers should reject mixing %ETHTOOL_FEC_AUTO_BIT with other
+ * FEC modes, because it's unclear whether in this case other modes constrain
+ * AUTO or are independent choices.
+ * Drivers must reject SET requests if they support none of the requested modes.
+ *
+ * If device does not support FEC drivers may use %ETHTOOL_FEC_NONE instead
+ * of returning %EOPNOTSUPP from %ETHTOOL_GFECPARAM.
+ *
+ * See enum ethtool_fec_config_bits for definition of valid bits for both
+ * @fec and @active_fec.
  */
 struct ethtool_fecparam {
 	__u32   cmd;
@@ -1392,11 +1410,16 @@ struct ethtool_fecparam {
 
 /**
  * enum ethtool_fec_config_bits - flags definition of ethtool_fec_configuration
- * @ETHTOOL_FEC_NONE: FEC mode configuration is not supported
- * @ETHTOOL_FEC_AUTO: Default/Best FEC mode provided by driver
+ * @ETHTOOL_FEC_NONE: FEC mode configuration is not supported. Should not
+ *		      be used together with other bits. GET only.
+ * @ETHTOOL_FEC_AUTO: Select default/best FEC mode automatically, usually based
+ *		      link mode and SFP parameters read from module's EEPROM.
+ *		      This bit does _not_ mean autonegotiation.
  * @ETHTOOL_FEC_OFF: No FEC Mode
- * @ETHTOOL_FEC_RS: Reed-Solomon Forward Error Detection mode
- * @ETHTOOL_FEC_BASER: Base-R/Reed-Solomon Forward Error Detection mode
+ * @ETHTOOL_FEC_RS: Reed-Solomon FEC Mode
+ * @ETHTOOL_FEC_BASER: Base-R/Reed-Solomon FEC Mode
+ * @ETHTOOL_FEC_LLRS: Low Latency Reed Solomon FEC Mode (25G/50G Ethernet
+ *		      Consortium)
  */
 enum ethtool_fec_config_bits {
 	ETHTOOL_FEC_NONE_BIT,