i2c/pca954x: Initialize the mux to disconnected state
pca954x power-on default is channel 0 connected. If multiple pca954x muxes are connected to the same physical I2C bus, the parent bus will see channel 0 devices behind both muxes by default. This is bad. Scenario: -- pca954x @ 0x70 -- ch 0 (I2C-bus-101) -- EEPROM @ 0x50 | I2C-bus-1 --- | -- pca954x @ 0x71 -- ch 0 (I2C-bus-111) -- EEPROM @ 0x50 1. Load I2C bus driver: creates I2C-bus-1 2. Load pca954x driver: creates virtual I2C-bus-101 and I2C-bus-111 3. Load eeprom driver 4. Try to read EEPROM @ 0x50 on I2C-bus-101. The transaction will also bleed onto I2C-bus-111 because pca954x @ 0x71 channel 0 is connected by default. Fix: Initialize pca954x to disconnected state in pca954x_probe() Signed-off-by: Petri Gynther <pgynther@google.com> Signed-off-by: Jean Delvare <khali@linux-fr.org> Cc: stable@kernel.org
This commit is contained in:
parent
9b640f2e15
commit
cd823db8b1
|
@ -201,10 +201,11 @@ static int pca954x_probe(struct i2c_client *client,
|
||||||
|
|
||||||
i2c_set_clientdata(client, data);
|
i2c_set_clientdata(client, data);
|
||||||
|
|
||||||
/* Read the mux register at addr to verify
|
/* Write the mux register at addr to verify
|
||||||
* that the mux is in fact present.
|
* that the mux is in fact present. This also
|
||||||
|
* initializes the mux to disconnected state.
|
||||||
*/
|
*/
|
||||||
if (i2c_smbus_read_byte(client) < 0) {
|
if (i2c_smbus_write_byte(client, 0) < 0) {
|
||||||
dev_warn(&client->dev, "probe failed\n");
|
dev_warn(&client->dev, "probe failed\n");
|
||||||
goto exit_free;
|
goto exit_free;
|
||||||
}
|
}
|
||||||
|
|
Loading…
Reference in New Issue