Hi,
Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> writes:
>> >> allow usb_del_gadget_udc() and usb add_gadget_udc() to be called
>> >> repeatedly on the same gadget->dev structure.
>> >>
>> >> We need to clear the gadget->dev structure so that kobject_init()
>> >> doesn't complain about already initialized object.
>> >>
>> >> Signed-off-by: Roger Quadros <rogerq@xxxxxx>
>> >> ---
>> >> drivers/usb/gadget/udc/core.c | 1 +
>> >> 1 file changed, 1 insertion(+)
>> >>
>> >> diff --git a/drivers/usb/gadget/udc/core.c b/drivers/usb/gadget/udc/core.c
>> >> index d685d82..efce68e 100644
>> >> --- a/drivers/usb/gadget/udc/core.c
>> >> +++ b/drivers/usb/gadget/udc/core.c
>> >> @@ -1273,6 +1273,7 @@ void usb_del_gadget_udc(struct usb_gadget *gadget)
>> >> flush_work(&gadget->work);
>> >> device_unregister(&udc->dev);
>> >> device_unregister(&gadget->dev);
>> >> + memset(&gadget->dev, 0x00, sizeof(gadget->dev));
>> >> }
>> >> EXPORT_SYMBOL_GPL(usb_del_gadget_udc);
>> >
>> > Isn't this dangerous? It's quite possible that the device_unregister()
>>
>> not on the gadget API, no.
>>
>> > call on the previous line invokes the gadget->dev.release callback,
>> > which might deallocate gadget. If that happens, your new memset will
>> > oops.
>>
>> that won't happen. struct usb_gadget is a member of the UDC's private
>> structure, like this:
>>
>> struct dwc3 {
>> [...]
>> struct usb_gadget gadget;
>> struct usb_gadget_driver *gadget_driver;
>> [...]
>> };
>
> Yes. So what? Can't the UDC driver use the refcount inside struct
> usb_gadget to control the lifetime of its private structure?
nope, not being used. At least not yet.
> (By the way, can you tell what's going on in net2280.c? I must be
> missing something; it looks like gadget_release() would quickly run
> into problems because it calls dev_get_drvdata() for &gadget->dev, but
> net2280_probe() never calls dev_set_drvdata() for that device.
> Furthermore, net2280_remove() continues to reference the net2280 struct
> after calling usb_del_gadget_udc(), and it never does seem to do a
> final put.)
static int net2280_probe(struct pci_dev *pdev, const struct pci_device_id *id)
{
struct net2280 *dev;
unsigned long resource, len;
void __iomem *base = NULL;
int retval, i;
/* alloc, and start init */
dev = kzalloc(sizeof(*dev), GFP_KERNEL);
if (dev == NULL) {
retval = -ENOMEM;
goto done;
}
pci_set_drvdata(pdev, dev);
^^^^^^^^^^^^^^^^^^^^^^^^^^^
>> I'm actually thinking that struct usb_gadget shouldn't have a struct
>> device at all. Just a pointer to a device, that would solve all these
>> issues.
>
> A pointer to which device? The UDC? That would change the directory
> layout in sysfs.
indeed. Would that be a problem?
> Or a pointer to a separate dynamically allocated device (the way struct
> usb_hcd contains a pointer to the root hub device)? That would work.
> If the UDC driver wanted to re-register the gadget, it would have to
> allocate a new device.
That could be done as well, if maintaining the directory structure is a
must.
--
balbi
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