[U-Boot] [PATCH] usb_ether: register usb ethernet gadget at each eth init

[Vitaly Kuzmichev]

Hi Lei,

Lei Wen wrote:
> Hi Vitaly,
> [...]
>>> +     if (usb_gadget_register_driver(&eth_driver) < 0)
>>> +             goto fail;
>>
>> You probably need then at least to remove usb_gadget_register_driver
>> call from usb_eth_initialize. And add usb_gadget_unregister_driver in
>> usb_eth_halt.
> 
> I am afraid that remove usb_gadget_register_driver call from usb_eth_initialize
> is not possible. For tftp as example, it would call eth_halt before
> the eth_init.
> If we do the remove behavior, the gadget still not valid yet in the
> first eth_halt call
> which would cause the uboot becomes halt.

The gadget driver handles this properly. Right now it just does
usb_gadget_disconnect which has no effect when no gadget was requested
from the UDC driver yet.
And additional calling of usb_gadget_unregister_driver will at most
return an error.

>> For example, my UDC driver returns EBUSY if another gadget driver tries
>> to register itself. (Yes, I do not want to have more than 1 gadget).
>> With your patch the gadget driver will fail each time when initializing.
>> Anyway if I "fix" my UDC driver some day the Ether gadget will try to
>> register itself twice (and more times later). So I will have to protect
>> it against this bad behavior.
> 
> Two gadget example may comes from what I am using now.
> I am current attempting to make the tftp and fastboot cowork togetther.
> Since fastboot is a cool tool, I think people may want it beside they
> still use the tftp.
> Would that be enough convincing?:)
> 
> I think the gadget driver should adopt like this to allow two gadget coexist.
> And from gadget driver's review, the switch from one gadget to another
> is easy, just
> register it to another should be enough. Does it really need to return EBUSY?

If the UDC (not a gadget) driver does not support more than 1 gadget
driver in the same time it must return an error (EBUSY is fine for now)
when another gadget tries to register itself.
The reason why does not it support 2 (and more) gadgets registered
simultaneously is another question. Even if I fix this, your patch is
not needed because the UDC driver will give USB requests to the
appropriate gadget driver properly.

I really do not understand what a problem with using 2 gadgets in the
same time without your patch if the UDC driver supports this.
Especially I do not understand...

> it is neccessary to do the register each time the
> eth begin to work to make usb gadget driver less confussed when
> we want to use two different usb gadget at the same time.

...how can the gadget (or UDC?) driver be confused here?
Right now I can tell that it will be more confused rather than less.
I just can suppose that you are trying to implement something like
switching active gadget driver in UDC driver which has only one variable
to store info about gadget driver (rather than having an array at
least). In this case you need to fix UDC driver rather than hacking all
available gadget drivers.
Also this way will not work when someone needs two gadgets active
simultaneously, e.g. USB ether with USB serial.


____
Best regards,
Vitaly.