linux-kernel - Re: [PATCH v2] iio: light: cm32181: Unregister second I2C client if present

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Date:   Wed, 22 Feb 2023 21:50:38 +0800
From:   Kai-Heng Feng <kai.heng.feng@...onical.com>
To:     Hans de Goede <hdegoede@...hat.com>
Cc:     ktsai@...ellamicro.com, jic23@...nel.org, lars@...afoo.de,
        linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] iio: light: cm32181: Unregister second I2C client if present

Hi Hans,

On Mon, Feb 13, 2023 at 7:17 PM Hans de Goede <hdegoede@...hat.com> wrote:
>
> Hi,
>
> Thank you for working on this, some remarks inline.
>
> On 2/8/23 08:21, Kai-Heng Feng 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>
> > ---
> > v2:
> >  - Use devm_add_action_or_reset() instead of remove() callback to avoid
> >    race.
> >
> >  drivers/iio/light/cm32181.c | 16 ++++++++++++++++
> >  1 file changed, 16 insertions(+)
> >
> > diff --git a/drivers/iio/light/cm32181.c b/drivers/iio/light/cm32181.c
> > index b1674a5bfa368..a3e5f56101c9f 100644
> > --- a/drivers/iio/light/cm32181.c
> > +++ b/drivers/iio/light/cm32181.c
> > @@ -429,6 +429,16 @@ static const struct iio_info cm32181_info = {
> >       .attrs                  = &cm32181_attribute_group,
> >  };
> >
> > +static void cm32181_disable(void *data)
> > +{
> > +     struct i2c_client *client = data;
> > +     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_probe(struct i2c_client *client)
> >  {
> >       struct device *dev = &client->dev;
> > @@ -479,6 +489,12 @@ static int cm32181_probe(struct i2c_client *client)
> >               return ret;
> >       }
> >
> > +     ret = devm_add_action_or_reset(dev, cm32181_disable, client);
> > +     if (ret) {
> > +             dev_err(dev, "%s: add devres action failed\n", __func__);
> > +             return ret;
> > +     }
> > +
>
> This is too late, we will still exit without unregistering the client if
> the cm32181_reg_init() call fails.
>
> It would be best to do this directly after the i2c_acpi_new_device()
> call, so inside the "if (ACPI_HANDLE(dev) && client->addr == SMBUS_ALERT_RESPONSE_ADDRESS) {"
> block.

You are right, not sure what I was thinking but this is much better.

>
> This way you can also remove the "if (cm32181->client != client)"
> check from cm32181_disable() since it now only runs when the client
> was registered in the first place.
>
> Also please rename cm32181_disable() to cm32181_unregister_dummy_client()
> so that the name actually matches what it does.

Sure, will change that in next version.

>
> Regards,
>
> Hans
>
>
>
>
>
> >       ret = devm_iio_device_register(dev, indio_dev);
> >       if (ret) {
> >               dev_err(dev, "%s: regist device failed\n", __func__);
>