[PATCH 4.9 21/38] eeprom: at24: correctly set the size for at24mac402

Greg Kroah-Hartman
2017-12-04T16:02:08Z

From: Bartosz Golaszewski <brgl@bgdev.pl>

commit 5478e478eee3b096b8d998d4ed445da30da2dfbc upstream.

There's an ilog2() expansion in AT24_DEVICE_MAGIC() which rounds down
the actual size of EUI-48 byte array in at24mac402 eeproms to 4 from 6,
making it impossible to read it all.

Fix it by manually adjusting the value in probe().

This patch contains a temporary fix that is suitable for stable
branches. Eventually we'll probably remove the call to ilog2() while
converting the magic values to actual structs.

Fixes: 0b813658c115 ("eeprom: at24: add support for at24mac series")
Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/misc/eeprom/at24.c | 10 ++++++++++
1 file changed, 10 insertions(+)

--- a/drivers/misc/eeprom/at24.c
+++ b/drivers/misc/eeprom/at24.c
@@ -639,6 +639,16 @@ static int at24_probe(struct i2c_client
dev_warn(&client->dev,
"page_size looks suspicious (no power of 2)!\n");

+ /*
+ * REVISIT: the size of the EUI-48 byte array is 6 in at24mac402, while
+ * the call to ilog2() in AT24_DEVICE_MAGIC() rounds it down to 4.
+ *
+ * Eventually we'll get rid of the magic values altoghether in favor of
+ * real structs, but for now just manually set the right size.
+ */
+ if (chip.flags & AT24_FLAG_MAC && chip.byte_len == 4)
+ chip.byte_len = 6;
+
/* Use I2C operations unless we're stuck with SMBus extensions. */
if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) {
if (chip.flags & AT24_FLAG_ADDR16)