linux-kernel - Re: [PATCH v1 2/6] usb: otg: utils: add facilities in phy lib to support multiple PHYs of same type

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Date:	Tue, 22 Jan 2013 16:07:26 +0200
From:	Roger Quadros <rogerq@...com>
To:	Kishon Vijay Abraham I <kishon@...com>
CC:	<tony@...mide.com>, <balbi@...com>, <linux@....linux.org.uk>,
	<eballetbo@...il.com>, <javier@...hile0.org>,
	<gregkh@...uxfoundation.org>, <linux-usb@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>,
	<linux-omap@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<devicetree-discuss@...ts.ozlabs.org>
Subject: Re: [PATCH v1 2/6] usb: otg: utils: add facilities in phy lib to
 support multiple PHYs of same type

On 01/22/2013 11:58 AM, Kishon Vijay Abraham I wrote:
> In order to add support for multipe PHY's of the same type, new API's
> for adding PHY and getting PHY has been added. Now the binding
> information for the PHY and controller should be done in platform file
> using usb_bind_phy API. And for getting a PHY, the device pointer of the
> USB controller and an index should be passed. Based on the binding
> information that is added in the platform file, usb_get_phy_dev will return the
> appropriate PHY.
> Already existing API's to add and get phy by type is not removed. These
> API's are deprecated and will be removed once all the platforms start to
> use the new API.
> 
> Signed-off-by: Kishon Vijay Abraham I <kishon@...com>
> ---
>  drivers/usb/otg/otg.c   |  114 ++++++++++++++++++++++++++++++++++++++++++++++-
>  include/linux/usb/phy.h |   13 ++++++
>  2 files changed, 126 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/usb/otg/otg.c b/drivers/usb/otg/otg.c
> index 492ba2f..1f30b22 100644
> --- a/drivers/usb/otg/otg.c
> +++ b/drivers/usb/otg/otg.c
> @@ -36,6 +36,20 @@ static struct usb_phy *__usb_find_phy(struct list_head *list,
>  	return ERR_PTR(-ENODEV);
>  }
>  
> +static struct usb_phy *__usb_find_phy_dev(struct device *dev,
> +	struct list_head *list, u8 index)
> +{
> +	struct usb_phy_bind *phy_bind = NULL;
> +
> +	list_for_each_entry(phy_bind, list, list) {
> +		if (!(strcmp(phy_bind->dev_name, dev_name(dev))) &&
> +				phy_bind->index == index)
> +			return phy_bind->phy;

If the PHY driver has not yet called usb_add_phy_dev() (e.g. driver not yet loaeded)
then this will return NULL.

> +	}
> +
> +	return ERR_PTR(-ENODEV);
> +}
> +
>  static void devm_usb_phy_release(struct device *dev, void *res)
>  {
>  	struct usb_phy *phy = *(struct usb_phy **)res;
> @@ -112,6 +126,69 @@ err0:
>  EXPORT_SYMBOL(usb_get_phy);
>  
>  /**
> + * usb_get_phy_dev - find the USB PHY
> + * @dev - device that requests this phy
> + * @index - the index of the phy
> + *
> + * Returns the phy driver, after getting a refcount to it; or
> + * -ENODEV if there is no such phy.  The caller is responsible for
> + * calling usb_put_phy() to release that count.
> + *
> + * For use by USB host and peripheral drivers.
> + */
> +struct usb_phy *usb_get_phy_dev(struct device *dev, u8 index)
> +{
> +	struct usb_phy	*phy = NULL;
> +	unsigned long	flags;
> +
> +	spin_lock_irqsave(&phy_lock, flags);
> +
> +	phy = __usb_find_phy_dev(dev, &phy_bind_list, index);
> +	if (IS_ERR(phy)) {
> +		pr_err("unable to find transceiver\n");
> +		goto err0;
> +	}

Since NULL is not IS_ERR(), you will do a NULL pointer reference below.

In such cases we would want to use the deferred probe mechanism. So should we return
-EPROBE_DEFER?

> +
> +	get_device(phy->dev);
> +
> +err0:
> +	spin_unlock_irqrestore(&phy_lock, flags);
> +
> +	return phy;
> +}
> +EXPORT_SYMBOL(usb_get_phy_dev);
> +

--
cheers,
-roger
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