sfp: fix EEPROM reading in the case of non-SFF8472 SFPs

[ Upstream commit 2794ffc4 ]

The EEPROM reading was trying to read from the second EEPROM address
if we requested the last byte from the SFF8079 EEPROM, which caused a
failure when the second EEPROM is not present.  Discovered with a
S-RJ01 SFP module.  Fix this.

Fixes: 73970055 ("sfp: add SFP module support")
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/net/phy/sfp.c

@@ -667,20 +667,19 @@ static int sfp_module_eeprom(struct sfp *sfp, struct ethtool_eeprom *ee,
 		len = min_t(unsigned int, last, ETH_MODULE_SFF_8079_LEN);
 		len -= first;
 
-		ret = sfp->read(sfp, false, first, data, len);
+		ret = sfp_read(sfp, false, first, data, len);
 		if (ret < 0)
 			return ret;
 
 		first += len;
 		data += len;
 	}
-	if (first >= ETH_MODULE_SFF_8079_LEN &&
-	    first < ETH_MODULE_SFF_8472_LEN) {
+	if (first < ETH_MODULE_SFF_8472_LEN && last > ETH_MODULE_SFF_8079_LEN) {
 		len = min_t(unsigned int, last, ETH_MODULE_SFF_8472_LEN);
 		len -= first;
 		first -= ETH_MODULE_SFF_8079_LEN;
 
-		ret = sfp->read(sfp, true, first, data, len);
+		ret = sfp_read(sfp, true, first, data, len);
 		if (ret < 0)
 			return ret;
 	}