path: root/Documentation
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authorAndrey Smirnov <>2019-09-07 17:03:14 -0700
committerSascha Hauer <>2019-09-09 10:48:03 +0200
commitc1388eaf5d7021c8519f0dc8943be16d1c126454 (patch)
tree84a3b8d12298e82b4de4bb3cd1e4fd8d19786ec7 /Documentation
parente9352093ceb8ca6867d9ff543711743b36ea9112 (diff)
i2c/pca954x: Initialize the mux to disconnected state
Port of a Linux kernel commit cd823db8b1161ef0d756514d280715a576d65cc3 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 <> Signed-off-by: Jean Delvare <> Cc: Signed-off-by: Andrey Smirnov <> Signed-off-by: Sascha Hauer <>
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