Subject: Re: [PATCH 12/19] i2c: mux: pca954x: make use of raw_spinlock
 variants
To: Julia Cartwright <julia@ni.com>, Wolfram Sang <wsa@the-dreams.de>
References: <cover.1489015238.git.julia@ni.com>
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CC: <linux-kernel@vger.kernel.org>, Thomas Gleixner <tglx@linutronix.de>,
        <linux-i2c@vger.kernel.org>
From: Peter Rosin <peda@axentia.se>
Organization: Axentia Technologies AB
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Date: Thu, 16 Mar 2017 20:38:06 +0100
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On 2017-03-09 17:21, Julia Cartwright wrote:
> The pca954x i2c mux driver currently implements an irq_chip for handling
> interrupts; due to how irq_chip handling is done, it's necessary for the
> irq_chip methods to be invoked from hardirq context, even on a a
> real-time kernel.  Because the spinlock_t type becomes a "sleeping"
> spinlock w/ RT kernels, it is not suitable to be used with irq_chips.
> 
> A quick audit of the operations under the lock reveal that they do only
> minimal, bounded work, and are therefore safe to do under a raw spinlock.
> 
> Signed-off-by: Julia Cartwright <julia@ni.com>

Patch applied to the i2c-mux repo. Thanks!

Cheers,
peda