On Wed, Dec 18, 2024 at 10:19:40AM +0800, Ma Ke wrote:
> When device_add(&udev->dev) failed, calling put_device() to explicitly
> release udev->dev. And the routine which calls usb_new_device() does
> not call put_device() when an error occurs.
That is wrong.
usb_new_device() is called by hub_port_connect(). The code does:
status = usb_new_device(udev);
...
if (status)
goto loop_disable;
...
loop_disable:
hub_port_disable(hub, port1, 1);
loop:
usb_ep0_reinit(udev);
release_devnum(udev);
hub_free_dev(udev);
if (retry_locked) {
mutex_unlock(hcd->address0_mutex);
usb_unlock_port(port_dev);
}
usb_put_dev(udev);
And usb_put_dev() is defined in usb.c as:
void usb_put_dev(struct usb_device *dev)
{
if (dev)
put_device(&dev->dev);
}
So you see, if usb_new_device() returns a nonzero value then
put_device() _is_ called.
> As comment of device_add()
> says, 'if device_add() succeeds, you should call device_del() when you
> want to get rid of it. If device_add() has not succeeded, use only
> put_device() to drop the reference count'.
You are correct that if device_add() succeeds and a later call fails,
then usb_new_device() does not properly call device_del(). Please
rewrite your patch to fix only that problem.
Alan Stern
