linux-kernel - Re: [PATCH] regulator: core: Avoid debugfs: Directory ... already present! error

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Message-ID: <20210123102941.GK106851@ediswmail.ad.cirrus.com>
Date:   Sat, 23 Jan 2021 10:29:41 +0000
From:   Charles Keepax <ckeepax@...nsource.cirrus.com>
To:     Hans de Goede <hdegoede@...hat.com>
CC:     Mark Brown <broonie@...nel.org>,
        Liam Girdwood <lgirdwood@...il.com>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] regulator: core: Avoid debugfs: Directory ... already
 present! error

On Fri, Jan 22, 2021 at 07:32:50PM +0100, Hans de Goede wrote:
> Sometimes regulator_get() gets called twice for the same supply on the
> same device. This may happen e.g. when a framework / library is used
> which uses the regulator; and the driver itself also needs to enable
> the regulator in some cases where the framework will not enable it.
> 
> Commit ff268b56ce8c ("regulator: core: Don't spew backtraces on
> duplicate sysfs") already takes care of the backtrace which would
> trigger when creating a duplicate consumer symlink under
> /sys/class/regulator/regulator.%d in this scenario.
> 
> Commit c33d442328f5 ("debugfs: make error message a bit more verbose")
> causes a new error to get logged in this scenario:
> 
> [   26.938425] debugfs: Directory 'wm5102-codec-MICVDD' with parent 'spi-WM510204:00-MICVDD' already present!
> 
> There is no _nowarn variant of debugfs_create_dir(), but we can detect
> and avoid this problem by checking the return value of the earlier
> sysfs_create_link_nowarn() call.
> 
> Add a check for the earlier sysfs_create_link_nowarn() failing with
> -EEXIST and skip the debugfs_create_dir() call in that case, avoiding
> this error getting logged.
> 
> Fixes: c33d442328f5 ("debugfs: make error message a bit more verbose")
> Cc: Charles Keepax <ckeepax@...nsource.cirrus.com>
> Signed-off-by: Hans de Goede <hdegoede@...hat.com>
> ---

Reviewed-by: Charles Keepax <ckeepax@...nsource.cirrus.com>

Thanks,
Charles

> -	int err;
> +	int err = 0;
>  
> @@ -1663,8 +1663,8 @@ static struct regulator *create_regulator(struct regulator_dev *rdev,
>  
> -	regulator->debugfs = debugfs_create_dir(supply_name,
> -						rdev->debugfs);
> +	if (err != -EEXIST)
> +		regulator->debugfs = debugfs_create_dir(supply_name, rdev->debugfs);

There is a slight oddity here in that if this regulator has
no struct device we will still get the warning. However, I
am totally not clear on when/why a regulator might not have a
dev, and am fairly sure it isn't common. So my vote would be
to cross that bridge if we ever come to it.

Thanks,
Charles