linux-kernel - Re: [PATCH] regmap: do not call regmap_debugfs_init() from regmap_attach

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Message-ID: <20210726114751.GE4670@sirena.org.uk>
Date:   Mon, 26 Jul 2021 12:47:51 +0100
From:   Mark Brown <broonie@...nel.org>
To:     Matthias Schiffer <matthias.schiffer@...tq-group.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        David Lechner <david@...hnology.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] regmap: do not call regmap_debugfs_init() from
 regmap_attach_dev()

On Mon, Jul 26, 2021 at 09:36:27AM +0200, Matthias Schiffer wrote:
> regmap_debugfs_init() should never be called twice for the same regmap,
> as it initializes various fields of the regmap struct, including list
> heads and mutices. A visible symptom are messages like:
> 
>     debugfs: Directory 'dummy-iomuxc-gpr@...4000' with parent 'regmap'
>     already present!
> 
> This happened whenever regmap_attach_dev() was called for an existing
> regmap. Remove the call from regmap_attach_dev() and change
> __regmap_init() so that regmap_debugfs_init() is called exactly once.

The use case for regmap_attach_dev() is that there was no device when
the regmap was initially instantiated due to it running very early, we
want to attach the device when we figure out what it is which includes
setting up the debugfs stuff.  Whatever is managing to call this with
the same device as has already been set is clearly not that use case.

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