linux/drivers/i2c/muxes
Petri Gynther cd823db8b1 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
2011-06-29 11:36:11 +02:00
..
gpio-i2cmux.c i2c: Add generic I2C multiplexer using GPIO API 2011-01-10 22:11:23 +01:00
Kconfig i2c: Add generic I2C multiplexer using GPIO API 2011-01-10 22:11:23 +01:00
Makefile i2c: Add generic I2C multiplexer using GPIO API 2011-01-10 22:11:23 +01:00
pca954x.c i2c/pca954x: Initialize the mux to disconnected state 2011-06-29 11:36:11 +02:00
pca9541.c i2c/mux: Driver for PCA9541 I2C Master Selector 2010-10-24 18:16:58 +02:00