Subject: [PATCH 1/9] usb: otg: use try_module_get in all usb_get_phy functions and add missing module_put

From: [email-masked] (Roger Quadros)
Date: Mon, 4 Feb 2013 15:59:18 +0200

On 02/04/2013 03:24 PM, Sascha Hauer wrote:
> From: Marc Kleine-Budde <[email-masked]>
> 
> In patch "5d3c28b usb: otg: add device tree support to otg library"
> devm_usb_get_phy_by_phandle() was added. It uses try_module_get() to lock the
> phy driver in memory. The corresponding module_put() is missing in that patch.
> 
> This patch adds try_module_get() to usb_get_phy() and usb_get_phy_dev().
> Further the missing module_put() is added to usb_put_phy().
> 
> Signed-off-by: Marc Kleine-Budde <[email-masked]>
> Signed-off-by: Sascha Hauer <[email-masked]>
> ---
>  drivers/usb/otg/otg.c |   10 +++++++---
>  1 file changed, 7 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/usb/otg/otg.c b/drivers/usb/otg/otg.c
> index e181439..2bd03d2 100644
> --- a/drivers/usb/otg/otg.c
> +++ b/drivers/usb/otg/otg.c
> @@ -130,7 +130,7 @@ struct usb_phy *usb_get_phy(enum usb_phy_type type)
>  	spin_lock_irqsave(&phy_lock, flags);
>  
>  	phy = __usb_find_phy(&phy_list, type);
> -	if (IS_ERR(phy)) {
> +	if (IS_ERR(phy) || !try_module_get(phy->dev->driver->owner)) {
>  		pr_err("unable to find transceiver of type %s\n",
>  			usb_phy_type_string(type));
>  		goto err0;

There are 2 problems with this.

- If phy was found but try_module_get failed you are not returning error code.

- If phy was found and try_module_get fails we would want to use deferred probing,
since this case is possible if the phy module is not yet loaded and alive but can be in
the future.

I would change the code to

	if (IS_ERR(phy)) {
		pr_err("unable to find transceiver of type %s\n",
			usb_phy_type_string(type));
		goto err0;
	}

	if (!try_module_get(phy->dev->driver->owner)) {
		phy = ERR_PTR(-EPROBE_DEFER);
		goto err0;
	}

> @@ -228,7 +228,7 @@ struct usb_phy *usb_get_phy_dev(struct device *dev, u8 index)
>  	spin_lock_irqsave(&phy_lock, flags);
>  
>  	phy = __usb_find_phy_dev(dev, &phy_bind_list, index);
> -	if (IS_ERR(phy)) {
> +	if (IS_ERR(phy) || !try_module_get(phy->dev->driver->owner)) {
>  		pr_err("unable to find transceiver\n");
>  		goto err0;
>  	}
> @@ -301,8 +301,12 @@ EXPORT_SYMBOL(devm_usb_put_phy);
>   */
>  void usb_put_phy(struct usb_phy *x)
>  {
> -	if (x)
> +	if (x) {
> +		struct module *owner = x->dev->driver->owner;
> +
>  		put_device(x->dev);
> +		module_put(owner);
> +	}
>  }
>  EXPORT_SYMBOL(usb_put_phy);
>  
> 

cheers,
-roger