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
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@ -201,10 +201,11 @@ static int pca954x_probe(struct i2c_client *client,
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i2c_set_clientdata(client, data);
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/* Read the mux register at addr to verify
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* that the mux is in fact present.
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/* Write the mux register at addr to verify
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* that the mux is in fact present. This also
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* initializes the mux to disconnected state.
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*/
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if (i2c_smbus_read_byte(client) < 0) {
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if (i2c_smbus_write_byte(client, 0) < 0) {
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dev_warn(&client->dev, "probe failed\n");
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goto exit_free;
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}
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