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From: Alan Stern <stern@rowland.harvard.edu>
To: Erkka Talvitie <erkka.talvitie@vincit.fi>
Cc: gregkh@linuxfoundation.org, <linux-usb@vger.kernel.org>,
	<claus.baumgartner@med.ge.com>
Subject: RE: [RFCv1 1/1] USB: EHCI: Do not return -EPIPE when hub is disconnected
Date: Wed, 4 Dec 2019 09:24:12 -0500 (EST)
Message-ID: <Pine.LNX.4.44L0.1912040917500.3941-100000@netrider.rowland.org> (raw)
In-Reply-To: <020901d5aaa5$415457f0$c3fd07d0$@vincit.fi>

On Wed, 4 Dec 2019, Erkka Talvitie wrote:

> > > So if CERR == EHCI_TUNE_CERR and the QTD_PID != 1 (not IN) then we
> > > should return -EPIPE, as the existing code does.  But if QTD_PID == 1
> > > then the code should continue, as your patch does -- with one
> > > difference: Put the additional check for EHCI_TUNE_CERR between the
> > > tests for DBE and XACT instead of after XACT (because XACT would
> > > decrement CERR whereas DBE wouldn't).
> > 
> > Good point, I agree.
> > 
> > >
> > > Can you make that change and test it?
> > 
> > Sure, I have made the change and test it as soon as possible.
> 
> I am not actually totally sure if I understood you correctly, but I tested a change where the first stall check is like this (PID_CODE_IN is defined as 1):
> 
> -               } else if (QTD_CERR(token)) {
> +               } else if (QTD_CERR(token) && (QTD_PID (token) != PID_CODE_IN)) {
>                         status = -EPIPE;
> 
> And the second stall check (now between DBE and XACT):
> +               } else if (QTD_CERR(token)) {
> +                       status = -EPIPE;
> 
> Is this what you meant? Please correct me if I am wrong.

Actually, what I meant for the first part was:

		} else if (QTD_CERR(token) &&
				(QTD_CERR(token) < EHCI_TUNE_CERR ||
				 QTD_PID(token) != PID_CODE_IN)) {

And of course there should be a comment before this line, explaining 
what it does.  By the way, the accepted format for multi-line comments 
is:

		/*
		 * Blah blah blah
		 * Blah blah blah
		 */

The second part of the patch looks okay (but again, with a comment).

> Anyways with these changes the issue does not reproduce.

Very good.

Alan Stern


  reply index

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-11-29 14:08 Erkka Talvitie
2019-12-02 19:43 ` Alan Stern
2019-12-03  9:38   ` Erkka Talvitie
2019-12-03 10:54     ` Erkka Talvitie
2019-12-03 13:35       ` Erkka Talvitie
2019-12-03 19:01     ` Alan Stern
2019-12-04  8:55       ` Erkka Talvitie
2019-12-04 13:18         ` Erkka Talvitie
2019-12-04 14:24           ` Alan Stern [this message]
2019-12-04 14:37             ` Erkka Talvitie
2019-12-05 10:35               ` Erkka Talvitie
2019-12-05 14:37                 ` Alan Stern
2019-12-05 15:00                   ` Erkka Talvitie
2019-12-09  9:57                     ` Erkka Talvitie
2019-12-09 15:24                       ` Alan Stern
2019-12-10  6:31                         ` Erkka Talvitie

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