mii: Add mii_advertise_flowctrl()

This converts flow control capabilites to an advertising mask and can
be useful in combination with mii_resolve_flowctrl_fdx().

Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/mii.h

@@ -239,6 +239,22 @@ static inline unsigned int mii_duplex (unsigned int duplex_lock,
 	return 0;
 }
 
+/**
+ * mii_advertise_flowctrl - get flow control advertisement flags
+ * @cap: Flow control capabilities (FLOW_CTRL_RX, FLOW_CTRL_TX or both)
+ */
+static inline u16 mii_advertise_flowctrl(int cap)
+{
+	u16 adv = 0;
+
+	if (cap & FLOW_CTRL_RX)
+		adv = ADVERTISE_PAUSE_CAP | ADVERTISE_PAUSE_ASYM;
+	if (cap & FLOW_CTRL_TX)
+		adv ^= ADVERTISE_PAUSE_ASYM;
+
+	return adv;
+}
+
 /**
  * mii_resolve_flowctrl_fdx
  * @lcladv: value of MII ADVERTISE register