linux-kernel - Re: [PATCH] usb: dwc3: ep0: Fix the possible missed request for handling delay STATUS phase

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Message-ID: <87o9y1medz.fsf@linux.intel.com>
Date:   Fri, 17 Feb 2017 10:04:56 +0200
From:   Felipe Balbi <balbi@...nel.org>
To:     Baolin Wang <baolin.wang@...aro.org>
Cc:     Alan Stern <stern@...land.harvard.edu>,
        Greg KH <gregkh@...uxfoundation.org>,
        USB <linux-usb@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Linaro Kernel Mailman List <linaro-kernel@...ts.linaro.org>,
        Mark Brown <broonie@...nel.org>
Subject: Re: [PATCH] usb: dwc3: ep0: Fix the possible missed request for handling delay STATUS phase


Hi,

Baolin Wang <baolin.wang@...aro.org> writes:
>>> (One possible approach would be to have the setup routine return
>>> different values for explicit and implicit status stages -- for
>>> example, return 1 if it wants to submit an explicit status request.
>>> That wouldn't be very different from the current
>>> USB_GADGET_DELAYED_STATUS approach.)
>>
>> not really, no. The idea was for composite.c and/or functions to support
>> both methods (temporarily) and use "gadget->wants_explicit_stages" to
>> explicitly queue DATA and STATUS. That would mean that f_mass_storage
>> wouldn't have to return DELAYED_STATUS if
>> (gadget->wants_explicit_stages).
>>
>> After all UDCs are converted over and set wants_explicit_stages (which
>> should all be done in a single series), then we get rid of the flag and
>> the older method of DELAYED_STATUS.
>
> (Sorry for late reply due to my holiday)
> I also met the problem pointed by Alan, from my test, I still want to
> need one return value to indicate if it wants to submit an explicit
> status request. Think about the Control-IN with a data stage, we can
> not get the STATUS phase request from usb_ep_queue() call, and we need

why not? wLength tells you that this is a 3-stage transfer. Gadget
driver should be able to figure out that it needs to usb_ep_queue()
another request for status stage.

> to handle this STATUS phase request in dwc3_ep0_xfernotready(). But
> Control-OUT will get one 0-length IN request for the status stage from
> usb_ep_queue(), so we need one return value from setup routine to

no we don't :-)

> distinguish these in dwc3_ep0_xfernotready(), or we can not handle
> status request correctly. Maybe I missed something else.
>>
>>> On the other hand, I am very doubtful about requiring explicit setup
>>> requests.
>>
>> right, me too ;-)
>
> So do you suggest me continue to try to do this? Thanks.

explicit setup? no
explicit status? yes

If you don't wanna do it, it's fine :-) I'll just add to my TODO
list. It just depends on how much other tasks you have on your end ;-)

-- 
balbi

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