linux-kernel - Re: [PATCH] Fix Corruption issue in USB ftdi driver drivers/usb/serial/ftdi

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Date:	Mon, 14 Nov 2011 13:54:55 -0800
From:	Greg KH <greg@...ah.com>
To:	Andrew Worsley <amworsley@...il.com>
Cc:	Alan Cox <alan@...ux.intel.com>,
	Greg Kroah-Hartman <gregkh@...e.de>,
	Uwe Bonnes <bon@...ktron.ikp.physik.tu-darmstadt.de>,
	Johan Hovold <jhovold@...il.com>,
	Jean-Christophe PLAGNIOL-VILLARD <plagnioj@...osoft.com>,
	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Fix Corruption issue in USB ftdi driver
 drivers/usb/serial/ftdi_sio.c

On Thu, Nov 03, 2011 at 04:06:31PM +1100, Andrew Worsley wrote:
> Avoid unnecessary Control URBs that reset the data/parity or baud rate
> to the currently set settings which can cause the FTDI chip to glitch
> it's serial output and cause a corruption of a character it is
> currently outputting.
> 
> Signed-off-by: amworsley@...il.com
> 
> ---
> 
> ....
> > It shouldn't be unless the apps you are running are doing odd things.
> > I'd not expect parity to keep changing certainly. What may be occuring
> > is that some of these devices only handle RTS/CTS flow and force the
> > flag on, indicating it back to the app. If the app ignores that then it
> > may end up trying to clear it several times.
> 
> Okay - Thanks I will try stracing the process and see if it is issuing
> all the requests. I thought
> it might be the line discipline trying to flow control the input. I've
> lost my box for the moment so that
> will be tomorrow perhaps.
> 
> ....
> 
> >> +
> >>         /* NOTE These routines can get interrupted by
> >>            ftdi_sio_read_bulk_callback  - need to examine what this
> >> means - don't see any problems yet */
> >>
> >> +    if ((old_termios->c_cflag & (CSIZE|PARODD|CSTOPB|PARODD)) ==
> >> +        (termios->c_cflag & (CSIZE|PARODD|CSTOPB|PARODD)))
> >
> > I think you need
> >
> > CSIZE (for CS7/8 switch)
> > PARODD (parity odd/even)
> > CMSPAR (parity mark/space v odd/even)
> > CSTOPB (stop bits)
> >
> > while you have PARODD twice.
> >
> > Otherwise this looks correct.
> 
> 
>   Woops - yep that was wrong. I attach a new patch - with CMSPAR and
> PARENB which I assume is also parity related.

Much better, thanks, but the tabs all seem to have been removed from
this patch, making it impossible to apply.

Also, I need a "clean" patch, against the 3.1 tree at the least, in
order to be able to apply this, not against a previous version of your
patch.

Also, run your patch through the scripts/checkpatch.pl script to ensure
it is correct before sending it out.

Care to fix this up and resend so that I can apply this?

thanks,

greg k-h
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