From: Alan Stern <stern@rowland.harvard.edu>
To: Andrey Konovalov <andreyknvl@google.com>
Cc: Felipe Balbi <felipe.balbi@linux.intel.com>,
USB list <linux-usb@vger.kernel.org>,
Alexander Potapenko <glider@google.com>,
Dmitry Vyukov <dvyukov@google.com>
Subject: Re: Pass transfer_buffer to gadget drivers
Date: Fri, 7 Jun 2019 11:02:44 -0400 (EDT) [thread overview]
Message-ID: <Pine.LNX.4.44L0.1906071056380.1612-100000@iolanthe.rowland.org> (raw)
In-Reply-To: <CAAeHK+xxn1dSJBwBv7g=Mp3e9XARmJwb9JgjLjbDLx0rE+9tew@mail.gmail.com>
On Fri, 7 Jun 2019, Andrey Konovalov wrote:
> > > The problem is that I want to receive that data (from the data stage)
> > > from within my gadget driver module. But it's not passed to the
> > > setup() callback. And the question is: how do I do that then?
> >
> > I just caught up on this thread...
> >
> > The answer is simple: The gadget driver's setup() callback routine
> > submits a request for endpoint 0. The Data Stage data is sent or
> > received (depending on the direction encoded in the Setup information)
> > by this request.
>
> Ah, OK, got it, thanks!
>
> Although while looking at the dummy_hcd implementation, I saw that it
> accesses usb->transfer_buffer in case USB_REQ_GET_STATUS in
> handle_control_request(), which is called right before the setup()
> callback is called. So the data already available there without any
> additional requests. Is this an implementation detail that is specific
> to dummy_hcd?
Yes, it is. dummy-hcd is unusual in that it combines both a USB host
controller and a USB device controller in a single driver.
Normal UDC drivers do handle USB_REQ_GET_STATUS on their own without
requiring the use of an explicit usb_request, because they handle the
entire transfer internally and don't involve the gadget driver.
However, they don't have access to any transfer_buffer; all they can do
is exchange packets with the host.
Alan Stern
next prev parent reply other threads:[~2019-06-07 15:02 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-07 11:44 Pass transfer_buffer to gadget drivers Andrey Konovalov
2019-06-07 12:02 ` Felipe Balbi
2019-06-07 12:14 ` Andrey Konovalov
2019-06-07 12:25 ` Felipe Balbi
2019-06-07 12:32 ` Andrey Konovalov
2019-06-07 12:43 ` Felipe Balbi
2019-06-07 12:45 ` Andrey Konovalov
2019-06-07 14:04 ` Alan Stern
2019-06-07 14:38 ` Andrey Konovalov
2019-06-07 15:02 ` Alan Stern [this message]
2019-06-07 15:05 ` Andrey Konovalov
2019-06-18 13:31 ` Andrey Konovalov
2019-06-18 13:34 ` Andrey Konovalov
2019-06-18 13:53 ` Alan Stern
2019-06-19 6:36 ` Felipe Balbi
2019-06-28 16:44 ` Andrey Konovalov
2019-06-28 17:29 ` Andrey Konovalov
2019-06-28 18:07 ` Alan Stern
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