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

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Message-ID: <20160917101821.GB4753@katana>
Date:   Sat, 17 Sep 2016 12:18:21 +0200
From:   Wolfram Sang <wsa@...-dreams.de>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Bartosz Golaszewski <bgolaszewski@...libre.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Alexandre Courbot <gnurou@...il.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Vignesh R <vigneshr@...com>, Yong Li <yong.b.li@...el.com>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Ingo Molnar <mingo@...hat.com>, Peter Rosin <peda@...ntia.se>,
        linux-i2c <linux-i2c@...r.kernel.org>,
        linux-gpio <linux-gpio@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 0/4] gpio: fix an incorrect lockdep warning

On Sat, Sep 17, 2016 at 03:19:52AM +0200, Peter Zijlstra wrote:
> 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@...radead.org>

Oops, I overlooked that I need your ack as well :) Thanks!

> > 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...

Afraid so.


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