linux-kernel - Re: [PATCH v2 1/3] software node: Introduce device_add_software

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Date:   Wed, 13 Jan 2021 17:30:03 +0200
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Heikki Krogerus <heikki.krogerus@...ux.intel.com>
Cc:     Daniel Scally <djrscally@...il.com>,
        Felipe Balbi <balbi@...nel.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org,
        linux-acpi@...r.kernel.org
Subject: Re: [PATCH v2 1/3] software node: Introduce
 device_add_software_node()

On Wed, Jan 13, 2021 at 01:39:18PM +0200, Heikki Krogerus wrote:
> On Wed, Jan 13, 2021 at 12:40:03AM +0000, Daniel Scally wrote:
> > On 11/01/2021 14:10, Heikki Krogerus wrote:

...

> > > +/**
> > > + * device_remove_software_node - Remove device's software node
> > > + * @dev: The device with the software node.
> > > + *
> > > + * This function will unregister the software node of @dev.
> > > + */
> > > +void device_remove_software_node(struct device *dev)
> > > +{
> > > +	struct swnode *swnode;
> > > +
> > > +	swnode = dev_to_swnode(dev);
> > > +	if (!swnode)
> > > +		return;
> > > +
> > > +	kobject_put(&swnode->kobj);
> > > +}
> > > +EXPORT_SYMBOL_GPL(device_remove_software_node);
> > 
> > I wonder if this also ought to set dev_fwnode(dev)->secondary back to
> > ERR_PTR(-ENODEV)?

Actually it's a good question.

> We can't do that here unfortunately. Other places still have a
> reference to the swnode at this point and they may still need to
> access it using the dev_fwnode(dev)->secondary pointer.

Yeah, but in this case we potentially leave a dangling pointer when last of the
user gone and kobject_put() will call for release.

-- 
With Best Regards,
Andy Shevchenko