On Tue, Feb 18, 2003 at 09:56:55AM +0100, Thomas Jarosch wrote:
> > > Okay, I've collected more information:
> > > I commented out the ftdi_write/ftdi_read function pointers in ftdi_sio.c,
> > > so that the generic handler of usbserial handles the write calls.
> > >
> > > Attached you'll find the debug log of usbserial showing the same behavior.
> > > Looks like the problem is not the ftdi_sio driver, it's in an upstream layer.
> > >
> > > Any hints how I could proceed now?
> >
> > Are you sure your userspace program isn't dropping the bytes? I find it
> > hard to believe that the tty layer could be doing it.
>
> Attached you'll find the source of my test application.
> It opens /dev/ttyUSB0 and starts writing data using normal write().
> As you can see in the debug log, no data is lost, the data is just wrong.
> (and splitted in a very strange way and the zero byte write requests
> are also a bit concerning)
This is a tty port, so you can't just open it and start writing data to
it and expect everything to be ok. You need to make sure the line
settings are set up properly first. Take a look at one of the many
serial port programming HOWTOs for examples of how to do this.
I also have a small loopback test program in perl around here somewhere
that I use all the time to verify that no data is being dropped on
either the write or read side. Ah, here it is:
kernel.org/pub/linux/kernel/people/gregkh/misc/serial_loopback.pl
So in short, fix the application and then see if you are still having
messed up data.
thanks,
greg k-h
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