Re: question on usb_suspend_interface()

On Mon, 12 Feb 2007, Oliver Neukum wrote:

> Hi,
> 
> concerning this code from usb_suspend_interface(), what keeps "driver"
> valid? I can see pm_lock protecting against usb_claim_interface(), but
> what about driver (un)registration?
> 
> 	driver = to_usb_driver(intf->dev.driver);
> 
> 	if (driver->suspend && driver->resume) {
> 		status = driver->suspend(intf, msg);

There are two ways a driver can be unbound from an interface.  The usual 
way is to unregister the driver, which would call through 
driver.c:usb_unbind_interface(), which calls usb_autoresume_device().  
That would force it to wait until usb_suspend_interface() finished.

The other way is to call usb_driver_release_interface().  I assumed this
would happen only as part of unregistering the driver.  If it occurs at
some other time then "driver" might indeed be NULL.  It wouldn't be hard 
to add synchronization, if you really think it is needed.

Alan Stern


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