Re: [PATCH, RFC] USBIP protocol documentation

From: Greg KH
Date: Tue Aug 09 2011 - 10:23:11 EST

On Tue, Aug 09, 2011 at 05:23:14PM +0800, David Chang wrote:
> Hi Greg,
> 2011/6/28 Németh Márton <nm127@xxxxxxxxxxx>:
> > From: Márton Németh <nm127@xxxxxxxxxxx>
> >
> > USBIP v1.0.0 protocol documentation.
> >
> > Signed-off-by: Márton Németh <nm127@xxxxxxxxxxx>
> > ---
> >
> > Hi,
> >
> > I tried to document the USBIP protocol as implemented in the Linux kernel 3.0-rc2.
> >
> > The description is a preliminary draft only, it may contain mistakes. I tried
> > to document what I have understand from the source code and from the actual
> > captured network traffic when the USBIP is in action. Please review it, correct it,
> > point out the missing parts.
> >
> > During I have documented the protocol a question came into my mind: why do we
> > have two different type of package when the URB completition handler is called,
> > namely USB_RET_SUBMIT and USBIP_RET_UNLINK? As far as I can see this causes race
> > condition because for one URB the completition handler is only called once. If
> > the one URB is sent in with USB_CMD_SUBMIT and then unlinked with USB_CMD_UNLINK
> > the completition handler is called only once. In the protocol, however, we have
> > two different type of packets: USB_RET_SUBMIT and USBIP_RET_UNLINK. The status
> > field of these messages may contain anything in this case depending on the timing.
> >
> > Regards,
> >
> >        Márton Németh
> Sorry, just one question about the usbip protocol document.
> I would like to know why didn't you apply this patch.

Because it was sent as a "RFC" (i.e. request for comments) and based on
the discussion afterward, there were lots of comments :)

If someone wants to resend it to me, without that marking, I'll be glad
to apply it.


greg k-h
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