linux-kernel - Re: [PATCH] iio: light: cm32181: Unregister second I2C client if present

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Message-ID: <20230206143637.00001b00@Huawei.com>
Date:   Mon, 6 Feb 2023 14:36:37 +0000
From:   Jonathan Cameron <Jonathan.Cameron@...wei.com>
To:     Kai-Heng Feng <kai.heng.feng@...onical.com>
CC:     <ktsai@...ellamicro.com>, <jic23@...nel.org>, <lars@...afoo.de>,
        <hdegoede@...hat.com>, <linux-iio@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] iio: light: cm32181: Unregister second I2C client if
 present

On Mon,  6 Feb 2023 14:36:16 +0800
Kai-Heng Feng <kai.heng.feng@...onical.com> wrote:

> If a second client that talks to the actual I2C address was created in
> probe(), there should be a corresponding cleanup in remove() to avoid
> leakage.
> 
> So if the "client" is not the same one used by I2C core, unregister it
> accordingly.
> 
> Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2152281
> Fixes: c1e62062ff54 ("iio: light: cm32181: Handle CM3218 ACPI devices with 2 I2C resources")
> Signed-off-by: Kai-Heng Feng <kai.heng.feng@...onical.com>

Whilst this fixes the leak, it introduces a race between unregistering
some of the hardware and the later removal of userspace interfaces. 
This needs to be handled via a devm_add_action_or_reset()
registered handler so it's automatically cleaned up at the right place
in the driver remove flow.

Jonathan


> ---
>  drivers/iio/light/cm32181.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/drivers/iio/light/cm32181.c b/drivers/iio/light/cm32181.c
> index b1674a5bfa368..37439e103d273 100644
> --- a/drivers/iio/light/cm32181.c
> +++ b/drivers/iio/light/cm32181.c
> @@ -488,6 +488,15 @@ static int cm32181_probe(struct i2c_client *client)
>  	return 0;
>  }
>  
> +static void cm32181_remove(struct i2c_client *client)
> +{
> +	struct cm32181_chip *cm32181 = iio_priv(i2c_get_clientdata(client));
> +
> +	/* Unregister the dummy client */
> +	if (cm32181->client != client)
> +		i2c_unregister_device(cm32181->client);
> +}
> +
>  static int cm32181_suspend(struct device *dev)
>  {
>  	struct cm32181_chip *cm32181 = iio_priv(dev_get_drvdata(dev));
> @@ -531,6 +540,7 @@ static struct i2c_driver cm32181_driver = {
>  		.pm = pm_sleep_ptr(&cm32181_pm_ops),
>  	},
>  	.probe_new	= cm32181_probe,
> +	.remove		= cm32181_remove,
>  };
>  
>  module_i2c_driver(cm32181_driver);