[PATCH 4.9 20/38] eeprom: at24: fix reading from 24MAC402/24MAC602

[Greg Kroah-Hartman]

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Heiner Kallweit <hkallweit1@xxxxxxxxx>

commit 644a1f19c6c8393d0c4168a5adf79056da6822eb upstream.

Chip datasheet mentions that word addresses other than the actual
start position of the MAC delivers undefined results. So fix this.
Current implementation doesn't work due to this wrong offset.

Fixes: 0b813658c115 ("eeprom: at24: add support for at24mac series")
Signed-off-by: Heiner Kallweit <hkallweit1@xxxxxxxxx>
Signed-off-by: Bartosz Golaszewski <brgl@xxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/misc/eeprom/at24.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/drivers/misc/eeprom/at24.c
+++ b/drivers/misc/eeprom/at24.c
@@ -365,7 +365,8 @@ static ssize_t at24_eeprom_read_mac(stru
 	memset(msg, 0, sizeof(msg));
 	msg[0].addr = client->addr;
 	msg[0].buf = addrbuf;
-	addrbuf[0] = 0x90 + offset;
+	/* EUI-48 starts from 0x9a, EUI-64 from 0x98 */
+	addrbuf[0] = 0xa0 - at24->chip.byte_len + offset;
 	msg[0].len = 1;
 	msg[1].addr = client->addr;
 	msg[1].flags = I2C_M_RD;