usb/149675: uftdi doesn't react to break properly

[Hans Petter Selasky]

The following reply was made to PR usb/149675; it has been noted by GNATS.

From: Hans Petter Selasky <hselasky at c2i.net>
To: Paul Thornton <prt at prt.org>
Cc: freebsd-usb at freebsd.org,
 freebsd-gnats-submit at freebsd.org,
 ed at freebsd.org
Subject: Re: usb/149675: uftdi doesn't react to break properly
Date: Sun, 15 Aug 2010 21:11:59 +0200

 On Sunday 15 August 2010 20:57:44 Paul Thornton wrote:
 > Hi,
 > 
 > Hans Petter Selasky wrote:
 > > I believe the following patch will fix your problem. Please apply and
 > > rebuild kernel / ucom module.
 > 
 > That has made a dramatic difference - things now look much better.
 > Thank you very much for that.
 > 
 > I'm still seeing a slight problem though.  In my test setup, I have a PC
 > (Windows but that shouldn't matter!) running an appplication which
 > transmits a break followed by the 513 data bytes - and this repeats
 > continually at near line-rate at 250kbaud.
 > 
 > Pre-patching, FreeBSD was unable to keep data byte 1 in location 1 at
 > all - it appeared randomly wherever it happened to be due to the lack of
 > break clearing the input buffer, and as the data dump of the buffer
 > refreshed, the values moved around as the breaks were turning up as datab.
 > 
 > After I've applied the patch, it starts off well - data byte 1 is in
 > location 1, but every 5-10 seconds there is a shift by a byte suggesting
 > that an extra byte has been received.  Is there any way that a break
 > could still be creeping in to the data stream periodically?
 > 
 > Under Linux, the code runs properly and there is no movement of the data
 > bytes, so I'm reasonably confident that it isn't a bug of mine.
 > 
 > Paul.
 
 I guess you will have to turn on ucom and uftdi debugging knobs under 
 hw.usb.xxx to figure that out. USB is just forwarding what it gets from the 
 hardware.
 
 --HPS