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

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Message-ID: <0d57bcf5-0d82-1754-dc38-d4814b8bb138@redhat.com>
Date:   Mon, 6 Feb 2023 15:41:52 +0100
From:   Hans de Goede <hdegoede@...hat.com>
To:     Jonathan Cameron <Jonathan.Cameron@...wei.com>,
        Kai-Heng Feng <kai.heng.feng@...onical.com>
Cc:     ktsai@...ellamicro.com, jic23@...nel.org, lars@...afoo.de,
        linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] iio: light: cm32181: Unregister second I2C client if
 present

Hi,

On 2/6/23 15:36, Jonathan Cameron wrote:
> 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.

Good point, I missed that issue.

Regards,

Hans



>> ---
>>  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);
>