linux-kernel - Re: [PATCH v1 1/1] iio: dac: ad5770r: Put fwnode in error case during ->probe()

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Date:   Thu, 13 May 2021 18:09:22 +0100
From:   Jonathan Cameron <jic23@...nel.org>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     Alexandru Ardelean <ardeleanalex@...il.com>,
        Jonathan Cameron <Jonathan.Cameron@...wei.com>,
        linux-iio <linux-iio@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Michael Hennerich <Michael.Hennerich@...log.com>,
        Alexandru Tachici <alexandru.tachici@...log.com>
Subject: Re: [PATCH v1 1/1] iio: dac: ad5770r: Put fwnode in error case
 during ->probe()

On Thu, 13 May 2021 01:00:22 +0300
Andy Shevchenko <andy.shevchenko@...il.com> wrote:

> On Wednesday, May 12, 2021, Alexandru Ardelean <ardeleanalex@...il.com>
> wrote:
> 
> > On Mon, May 10, 2021 at 12:59 PM Andy Shevchenko
> > <andy.shevchenko@...il.com> wrote:  
> > >
> > > device_for_each_child_node() bumps a reference counting of a returned  
> > variable.  
> > > We have to balance it whenever we return to the caller.  
> >
> > This feels like the device_for_each_child_node() [and the of_node
> > variant] iterator[s] need[s] some re-design to account for how easy it
> > is to slip stuff by.  
> 
> 
> I don’t know how you can do it differently if you wish to give a guarantee
> that object doesn’t suddenly disappear while you are iterating over it.
> 
> Look at the bus_find_device() and similar APIs, they basically do the
> similar.
> 
> 
> 
> > But that's something quite out of this scope.
> >
> > Reviewed-by: Alexandru Ardelean <ardeleanalex@...il.com>
> >
> >  
> Thanks.
> 
Applied to the fixes-togreg branch of iio.git and marked for stable.

Thanks,

Joathan

> 
> > >
> > > Fixes: cbbb819837f6 ("iio: dac: ad5770r: Add AD5770R support")
> > > Cc: Alexandru Tachici <alexandru.tachici@...log.com>
> > > Signed-off-by: Andy Shevchenko <andy.shevchenko@...il.com>
> > > ---
> > >  drivers/iio/dac/ad5770r.c | 16 +++++++++++-----
> > >  1 file changed, 11 insertions(+), 5 deletions(-)
> > >
> > > diff --git a/drivers/iio/dac/ad5770r.c b/drivers/iio/dac/ad5770r.c
> > > index 7ab2ccf90863..8107f7bbbe3c 100644
> > > --- a/drivers/iio/dac/ad5770r.c
> > > +++ b/drivers/iio/dac/ad5770r.c
> > > @@ -524,23 +524,29 @@ static int ad5770r_channel_config(struct  
> > ad5770r_state *st)  
> > >         device_for_each_child_node(&st->spi->dev, child) {
> > >                 ret = fwnode_property_read_u32(child, "num", &num);
> > >                 if (ret)
> > > -                       return ret;
> > > -               if (num >= AD5770R_MAX_CHANNELS)
> > > -                       return -EINVAL;
> > > +                       goto err_child_out;
> > > +               if (num >= AD5770R_MAX_CHANNELS) {
> > > +                       ret = -EINVAL;
> > > +                       goto err_child_out;
> > > +               }
> > >
> > >                 ret = fwnode_property_read_u32_array(child,
> > >  
> > "adi,range-microamp",  
> > >                                                      tmp, 2);
> > >                 if (ret)
> > > -                       return ret;
> > > +                       goto err_child_out;
> > >
> > >                 min = tmp[0] / 1000;
> > >                 max = tmp[1] / 1000;
> > >                 ret = ad5770r_store_output_range(st, min, max, num);
> > >                 if (ret)
> > > -                       return ret;
> > > +                       goto err_child_out;
> > >         }
> > >
> > > +       return 0;
> > > +
> > > +err_child_out:
> > > +       fwnode_handle_put(child);
> > >         return ret;
> > >  }
> > >
> > > --
> > > 2.31.1
> > >  
> >  
> 
>