net: mdio-i2c: add support for Clause 45 accesses

Some SFP+ modules have PHYs on them just like SFP modules do, except
they are Clause 45 PHYs.  The I2C protocol used to access them is
modified slightly in order to send the device address and 16-bit
register index.

Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/phy/mdio-i2c.c

@@ -33,17 +33,24 @@ static int i2c_mii_read(struct mii_bus *bus, int phy_id, int reg)
 {
 	struct i2c_adapter *i2c = bus->priv;
 	struct i2c_msg msgs[2];
-	u8 data[2], dev_addr = reg;
+	u8 addr[3], data[2], *p;
 	int bus_addr, ret;
 
 	if (!i2c_mii_valid_phy_id(phy_id))
 		return 0xffff;
 
+	p = addr;
+	if (reg & MII_ADDR_C45) {
+		*p++ = 0x20 | ((reg >> 16) & 31);
+		*p++ = reg >> 8;
+	}
+	*p++ = reg;
+
 	bus_addr = i2c_mii_phy_addr(phy_id);
 	msgs[0].addr = bus_addr;
 	msgs[0].flags = 0;
-	msgs[0].len = 1;
-	msgs[0].buf = &dev_addr;
+	msgs[0].len = p - addr;
+	msgs[0].buf = addr;
 	msgs[1].addr = bus_addr;
 	msgs[1].flags = I2C_M_RD;
 	msgs[1].len = sizeof(data);
@@ -61,18 +68,23 @@ static int i2c_mii_write(struct mii_bus *bus, int phy_id, int reg, u16 val)
 	struct i2c_adapter *i2c = bus->priv;
 	struct i2c_msg msg;
 	int ret;
-	u8 data[3];
+	u8 data[5], *p;
 
 	if (!i2c_mii_valid_phy_id(phy_id))
 		return 0;
 
-	data[0] = reg;
-	data[1] = val >> 8;
-	data[2] = val;
+	p = data;
+	if (reg & MII_ADDR_C45) {
+		*p++ = (reg >> 16) & 31;
+		*p++ = reg >> 8;
+	}
+	*p++ = reg;
+	*p++ = val >> 8;
+	*p++ = val;
 
 	msg.addr = i2c_mii_phy_addr(phy_id);
 	msg.flags = 0;
-	msg.len = 3;
+	msg.len = p - data;
 	msg.buf = data;
 
 	ret = i2c_transfer(i2c, &msg, 1);