linux-kernel - Re: [RFT PATCH] power: bq2415x_charger: Properly handle ENODEV from power_supply_get_by

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Message-id: <1413371491.26771.15.camel@AMDC1943>
Date:	Wed, 15 Oct 2014 13:11:31 +0200
From:	Krzysztof Kozlowski <k.kozlowski@...sung.com>
To:	Sebastian Reichel <sre@...nel.org>
Cc:	Dmitry Eremin-Solenikov <dbaryshkov@...il.com>,
	David Woodhouse <dwmw2@...radead.org>,
	linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Subject: Re: [RFT PATCH] power: bq2415x_charger: Properly handle ENODEV from
 power_supply_get_by_phandle

On śro, 2014-10-15 at 11:05 +0200, Sebastian Reichel wrote:
> Hi Krzysztof,
> 
> On Tue, Oct 14, 2014 at 10:32:53AM +0200, Krzysztof Kozlowski wrote:
> > The power_supply_get_by_phandle() on error returns ENODEV or NULL.
> > The driver later expects obtained pointer to power supply to be
> > valid or NULL. If it is not NULL then it dereferences it in
> > bq2415x_notifier_call() which would lead to dereferencing ENODEV-value
> > pointer.
> > 
> > Properly handle the power_supply_get_by_phandle() error case and abort probe.
> > 
> > Signed-off-by: Krzysztof Kozlowski <k.kozlowski@...sung.com>
> > Fixes: faffd234cf85 ("bq2415x_charger: Add DT support")
> > Cc: <stable@...r.kernel.org>
> 
> That looks valid, but I guess this should change one more thing:
> 
> > ---
> >  drivers/power/bq2415x_charger.c | 7 ++++++-
> >  1 file changed, 6 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/power/bq2415x_charger.c b/drivers/power/bq2415x_charger.c
> > index e384844a1ae1..d9c457217b6a 100644
> > --- a/drivers/power/bq2415x_charger.c
> > +++ b/drivers/power/bq2415x_charger.c
> > @@ -1579,8 +1579,13 @@ static int bq2415x_probe(struct i2c_client *client,
> >  	if (np) {
> >  		bq->notify_psy = power_supply_get_by_phandle(np, "ti,usb-charger-detection");
> >  
> > -		if (!bq->notify_psy)
> > +		if (!bq->notify_psy) {
> >  			return -EPROBE_DEFER;
> 
> this also needs to goto error_2. I guess something as the following
> is needed:
> 
> if (IS_ERR_OR_NULL(bq->notify_psy)) {
>     if (bq->notify_psy)
>         dev_err(&client->dev, "no 'ti,usb-charger-detection' property\n");
>     ret = PTR_ERR(bq->notify_psy);
>     goto error_2;
> }

So you do not want to defer the probe? What if notified charger will
come online after this probe?

Second idea - now I think my change is not compatible with bindings
(documentation) and could break booting of existing boards which do not
provide the "ti,usb-charger-detection" property. For example
arch/arm/boot/dts/omap3-n900.dts

The "ti,usb-charger-detection" property is marked as optional but my
patch actually makes it required.

It should be rather like this:

if (IS_ERR(bq->notify_psy)) {
    bq->notify_psy = NULL;
    dev_info(&client->dev, "no 'ti,usb-charger-detection' property \n");
} else if (!bq->notify_psy) {
    ret = -EPROBE_DEFER;
    goto error_2;
}

What do you think?

Krzysztof

> > +		} else if (IS_ERR(bq->notify_psy)) {
> > +			dev_err(&client->dev, "no 'ti,usb-charger-detection' property\n");
> > +			ret = PTR_ERR(bq->notify_psy);
> > +			goto error_2;
> > +		}
> >  	}
> >  	else if (pdata->notify_device)
> >  		bq->notify_psy = power_supply_get_by_name(pdata->notify_device);
> 
> -- Sebastian

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