Re: [PATCH v2 0/4] gpio: fix an incorrect lockdep warning

[Peter Zijlstra]

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.

Acked-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>

> Note: if this series gets merged, I'll prepare follow-up patches for
> other expanders for which a similar problem could potentially occur.

We can't push this annotation into the i2c core, can we? Since the mutex
is in driver specific code, not more generic...