net: Add mii_resolve_flowctrl_fdx()

Add an mii helper function to resolve flow control status per
IEEE 802.3-2005 table 28B-3.
This function was taken from the Linux source tree.

Signed-off-by: Yuiko Oshino <yuiko.oshino@microchip.com>
Acked-by: Joe Hershberger <joe.hershberger@ni.com>

include/linux/mii.h

@@ -190,4 +190,27 @@ static inline unsigned int mii_duplex (unsigned int duplex_lock,
 	return 0;
 }
 
+/**
+ * mii_resolve_flowctrl_fdx
+ * @lcladv: value of MII ADVERTISE register
+ * @rmtadv: value of MII LPA register
+ *
+ * Resolve full duplex flow control as per IEEE 802.3-2005 table 28B-3
+ */
+static inline u8 mii_resolve_flowctrl_fdx(u16 lcladv, u16 rmtadv)
+{
+	u8 cap = 0;
+
+	if (lcladv & rmtadv & ADVERTISE_PAUSE_CAP) {
+		cap = FLOW_CTRL_TX | FLOW_CTRL_RX;
+	} else if (lcladv & rmtadv & ADVERTISE_PAUSE_ASYM) {
+		if (lcladv & ADVERTISE_PAUSE_CAP)
+			cap = FLOW_CTRL_RX;
+		else if (rmtadv & ADVERTISE_PAUSE_CAP)
+			cap = FLOW_CTRL_TX;
+	}
+
+	return cap;
+}
+
 #endif /* __LINUX_MII_H__ */