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
The underlying I2C adapter may or may not be present when this driver
gets initialized, and may disappear later, so there is no safe time at
which the probe and remove functions can be discarded.
Signed-off-by: Guenter Roeck <guenter.roeck@ericsson.com>
Signed-off-by: Jean Delvare <khali@linux-fr.org>
Petri Gynther