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

[Roger Quadros]

On 02/04/2013 04:10 PM, Marc Kleine-Budde wrote:
> On 02/04/2013 02:59 PM, Roger Quadros wrote:
>> On 02/04/2013 03:24 PM, Sascha Hauer wrote:
>>> From: Marc Kleine-Budde <mkl at pengutronix.de>
>>>
>>> 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 <mkl at pengutronix.de>
>>> Signed-off-by: Sascha Hauer <s.hauer at pengutronix.de>
>>> ---
>>>  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.
> 
> Correct - but....
> 
>> - 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.
> 
> ...this should not happen, as the phy list is protected by the
> spin_lock. If a phy driver module has added a the phy to the
> infrastructure, but has been rmmod'ed without removing the phy. The phy
> driver is broken anyway.
> 

Yes, you are right.

cheers,
-roger