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Date: Wed, 3 Mar 2010 15:50:46 +0100
From: Johan Hovold <jhovold@gmail.com>
To: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Greg KH <greg@kroah.com>, Peter Feuerer <peter@piie.net>,
       linux-kernel@vger.kernel.org
Subject: Re: [BUG] usb-serial / pl2302 corrupted receive
Message-ID: <20100303145046.GB15162@localhost>
References: <cone.1267466820.296261.3385.1000@deskpiie>
 <20100302235353.GB2196@kroah.com>
 <20100303121441.622e271f@lxorguk.ukuu.org.uk>
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On Wed, Mar 03, 2010 at 12:14:41PM +0000, Alan Cox wrote:
> > > Terminal1:
> > > cat /dev/ttyUSB1
> > > 
> > > Terminal2:
> > > while true; do echo 123456789012345678901234567890 > /dev/ttyUSB0 ; done
> > 
> > cat and echo are known to not work well with usb to serial devices.  Can
> > you duplicate this with a "real" tty program like minicom or something
> > else?
> 
> That should no longer be the case. The kfifo buffering implementation
> fixed all the broken internal buffering in the usb tty code - or should
> have done.

Actually, the per-bulk-out-point allocated kfifo is currently unsused for most
drivers, including the pl2303.

I'm responding to this mail with a patch (against 2.6.33) which replaces
the custom fifo-based write implementation in pl2303 with the generic
kfifo based one. I've used it for quite a while now without any problems
(just haven't got around to submitting it).

If Alan's correct, this might solve the echo/cat issue, but either way
it should be applied at some point as it removes a lot of duplicate code.

/Johan