linux-kernel - Re: [PATCH v1 5/6] usb: otg: add device tree support to otg library

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Date:	Tue, 22 Jan 2013 10:36:50 +0000
From:	Mark Rutland <mark.rutland@....com>
To:	Kishon Vijay Abraham I <kishon@...com>
Cc:	"tony@...mide.com" <tony@...mide.com>,
	"balbi@...com" <balbi@...com>,
	"linux@....linux.org.uk" <linux@....linux.org.uk>,
	"eballetbo@...il.com" <eballetbo@...il.com>,
	"javier@...hile0.org" <javier@...hile0.org>,
	"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
	"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-omap@...r.kernel.org" <linux-omap@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"devicetree-discuss@...ts.ozlabs.org" 
	<devicetree-discuss@...ts.ozlabs.org>,
	Marc Kleine-Budde <mkl@...gutronix.de>
Subject: Re: [PATCH v1 5/6] usb: otg: add device tree support to otg library

> +struct usb_phy *devm_usb_get_phy_by_phandle(struct device *dev,
> +	const char *phandle, u8 index)
> +{
> +	struct usb_phy	*phy = NULL, **ptr;
> +	unsigned long	flags;
> +	struct device_node *node;
> +
> +	if (!dev->of_node) {
> +		dev_dbg(dev, "device does not have a device node entry\n");
> +		return ERR_PTR(-EINVAL);
> +	}
> +
> +	node = of_parse_phandle(dev->of_node, phandle, index);
> +	if (!node) {
> +		dev_dbg(dev, "failed to get %s phandle in %s node\n", phandle,
> +			dev->of_node->full_name);
> +		return ERR_PTR(-ENODEV);
> +	}

At any point past this, node's refcount is incremented (done automatically by
of_parse_phandle => of_find_node_by_phandle).

> +
> +	ptr = devres_alloc(devm_usb_phy_release, sizeof(*ptr), GFP_KERNEL);
> +	if (!ptr) {
> +		dev_dbg(dev, "failed to allocate memory for devres\n");
> +		return ERR_PTR(-ENOMEM);
> +	}
> +
> +	spin_lock_irqsave(&phy_lock, flags);
> +
> +	phy = __of_usb_find_phy(node);
> +	if (IS_ERR(phy) || !try_module_get(phy->dev->driver->owner)) {
> +		phy = ERR_PTR(-EPROBE_DEFER);
> +		devres_free(ptr);
> +		goto err0;
> +	}
> +
> +	*ptr = phy;
> +	devres_add(dev, ptr);
> +
> +	get_device(phy->dev);
> +
> +err0:
> +	spin_unlock_irqrestore(&phy_lock, flags);
> +
> +	return phy;
> +}

This means that on all of the exit paths, node's refcount is left incremented
incorrectly. You'll need an of_node_put(node) on each exit path.

Thanks,
Mark.

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