linux-kernel - Re: [SOLVED] Serial buffer corruption [was Re: FTDI usb-serial possible bug]

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Message-ID: <463B46F4.6090906@microgate.com>
Date:	Fri, 04 May 2007 08:45:08 -0600
From:	Paul Fulghum <paulkf@...rogate.com>
To:	Antonino Ingargiola <tritemio@...il.com>
CC:	linux-usb-users@...ts.sourceforge.net, linux-kernel@...r.kernel.org
Subject: Re: [SOLVED] Serial buffer corruption [was Re: FTDI usb-serial possible
 bug]

Antonino Ingargiola wrote:
> Nope. In python I use the flushInput() method of the serial object
> defined by the pyserial library[0]. The method does just this system
> call:
> 
>     termios.tcflush(self.fd, TERMIOS.TCIFLUSH)
> 
> that I think is correct.

There is intermediate buffering between the driver and
the line discipline called the tty flip buffer.

receive data flow:
driver --> tty flip --> line discipline --> application

When you flush input, the line disciplines flush_buffer() method
is called to clear any data residing the in the line discipline.

This does not affect the tty flip buffer
or hardware receive FIFOs.

I suspect the biggest problem is the data in the
tty flip buffer.

A new function to flush the tty flip buffer needs to
be added and then called from tty_io.c:tty_ldisc_flush().

Then a call to tcflush(TCIFLUSH) will clear both buffers.

This still would not clear any data in the hardware
receive FIFOs.

-- 
Paul Fulghum
Microgate Systems, Ltd.
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