On Fri, Sep 16, 2016 at 06:02:41PM +0200, Bartosz Golaszewski wrote: > If an I2C GPIO multiplexer is driven by a GPIO provided by an expander > when there's a second expander using the same device driver on one of > the I2C bus segments, lockdep prints a deadlock warning when trying to > set the direction or the value of the GPIOs provided by the second > expander. > > This series exports an already existing function from i2c-core as > public API and reuses it in pca953x to pass a correct lock subclass > to lockdep. > > Note: if this series gets merged, I'll prepare follow-up patches for > other expanders for which a similar problem could potentially occur. > > Tested with the following setup: > > ------- --------- Bus segment 1 | | > | | | |--------------- Devices > | | SCL/SDA | | | | > | Linux |-----------| I2C MUX | - - - - - > | | | | | Bus segment 2 > | | | | |------------------- > ------- | --------- | > | | - - - - - > ------------ | MUX GPIO | | > | | | Devices > | GPIO | | | | > | Expander 1 |---- - - - - - > | | | > ------------ | SCL/SDA > | > ------------ > | | > | GPIO | > | Expander 2 | > | | > ------------ > > where expander 1 is a pca9534 and expander 2 is a pca9535. > > v1 -> v2: > - added patches 1/4, 2/4 & 3/4 > - used i2c_adapter_depth() in patch 4/4 in order to detect multiple > adapter nesting > > Bartosz Golaszewski (4): > i2c: export i2c_adapter_depth() > lockdep: make MAX_LOCKDEP_SUBCLASSES unconditionally visible > i2c: add a warning to i2c_adapter_depth() > gpio: pca953x: fix an incorrect lockdep warning Applied to for-next, thanks!
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