linux-kernel - Re: [PATCH 12/19] i2c: mux: pca954x: make use of raw

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Message-ID: <910fae4d-e5a7-f149-1daf-44e5487bf643@axentia.se>
Date:   Thu, 16 Mar 2017 20:38:06 +0100
From:   Peter Rosin <peda@...ntia.se>
To:     Julia Cartwright <julia@...com>, Wolfram Sang <wsa@...-dreams.de>
CC:     <linux-kernel@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        <linux-i2c@...r.kernel.org>
Subject: Re: [PATCH 12/19] i2c: mux: pca954x: make use of raw_spinlock
 variants

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@...com>

Patch applied to the i2c-mux repo. Thanks!

Cheers,
peda