From mboxrd@z Thu Jan  1 00:00:00 1970
References: <25f8de8836cc6c592e70cd662b61d0a2@hamnavoe.com>
From: Gorka Guardiola <paurea@gmail.com>
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In-Reply-To: <25f8de8836cc6c592e70cd662b61d0a2@hamnavoe.com>
Message-Id: <E593EC29-45DF-4AB3-B8E8-984938952567@gmail.com>
Date: Thu, 14 Feb 2013 20:54:00 +0100
To: Fans of the OS Plan 9 from Bell Labs <9fans@9fans.net>
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Subject: Re: [9fans] usb serial bug
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Yes, I am looking into it and just saw this.
G.

On Feb 14, 2013, at 8:24 PM, Richard Miller <9fans@hamnavoe.com> wrote:

> I said:
>
>>> The current Plan 9 usb architecture perpetuates the confusion by
>>> referring to them both with one name epN.1, but you still have to open
>>> them both independently.
>
> Erik replied:
>> in that case, shouldn't these three blocks be reverted?
>
> Erik is right, I was talking through my hat.  It's OK to open bulk
> endpoints read/write, and the kernel will do the right thing.  The
> actual problem, which neither of us had spotted although it was
> staring us in the face, is this:
>
>            if((ep->dir == Ein || ep->dir == Eboth) && epin == -1)
>                epin = ep->id;
>            if((ep->dir == Ein || ep->dir == Eboth) && epout == -1)
>                epout = ep->id;
>
> Notice the two occurrences of Ein?  The second one obviously should
> be Eout.  It was a typo (mine, I blush to admit).
>
> My usb serial adapter uses the same ep number for input and output,
> so my testing didn't reveal this error.  I think the same typo will
> account for the double-free bug which Jeff (and Lucio on 4 Feb) reported.
>
> Erik, Jeff, Lucio - please try changing the offending Ein to Eout in
> /sys/src/cmd/usb/serial/serial.c:721 and see if your troubles are resolved.
>
>