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

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

[Heiner Kallweit]

Chip datasheet mentions that word addresses other than the actual
start position of the MAC delivers undefined results. So fix this.

Fixes: 0b813658c115 "eeprom: at24: add support for at24mac series"
Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
---
 drivers/misc/eeprom/at24.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/misc/eeprom/at24.c b/drivers/misc/eeprom/at24.c
index e0b4b36ef..00d602be7 100644
--- a/drivers/misc/eeprom/at24.c
+++ b/drivers/misc/eeprom/at24.c
@@ -425,7 +425,8 @@ static ssize_t at24_eeprom_read_mac(struct at24_data *at24, char *buf,
 	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;
-- 
2.15.0

Re: [PATCH] eeprom: at24: fix reading from 24MAC402/24MAC602

[Bartosz Golaszewski]

2017-11-24 7:42 GMT+01:00 Heiner Kallweit <hkallweit1@gmail.com>:
> Chip datasheet mentions that word addresses other than the actual
> start position of the MAC delivers undefined results. So fix this.
>

Could you also mention in the commit message, that the current
implementation doesn't work because the offset is simply wrong?

Thanks,
Bartosz

> Fixes: 0b813658c115 "eeprom: at24: add support for at24mac series"
> Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
> ---
>  drivers/misc/eeprom/at24.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/misc/eeprom/at24.c b/drivers/misc/eeprom/at24.c
> index e0b4b36ef..00d602be7 100644
> --- a/drivers/misc/eeprom/at24.c
> +++ b/drivers/misc/eeprom/at24.c
> @@ -425,7 +425,8 @@ static ssize_t at24_eeprom_read_mac(struct at24_data *at24, char *buf,
>         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;
> --
> 2.15.0
>