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Date: Tue, 5 Oct 2010 06:33:12 -0700
From: Greg KH <gregkh@suse.de>
To: Raju Rameshwar Uprade <rajsingh@ncra.tifr.res.in>
Cc: linux-kernel@vger.kernel.org, linux-usb@vger.kernel.org
Subject: Re: pl2303_ttyUSB0 userspace application not able to control RTS
 line
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On Tue, Oct 05, 2010 at 04:33:16PM +0530, Raju Rameshwar Uprade wrote:
> Hi,
>    I am using a prolific tech USB-to-serial converter on linux kernel version 2.6.35.
> I wrote a userspace program to enable/disable RTS line which is working fine with
> standard serial port like ttyS0 and ttyS1.
> 
> But when I used the USB-to-serial port (ttyUSB0) to enable/disable the RTS line,ttyUSB0
> is not able to do that as well as some times gives
> 
> pl2303_ttyUSB0 : pl2303_open-failed submitting read urb -error 22.

Is this your "modified" driver?

I don't see that error in the kernel log below at all.

What kernel version is this?

And are you sure that your device actually has the RTS lines connected?
I have seen a number of these devices that do not bring those lines from
the chip to the rs232 connection.

You really might want to go purchase a "real" usb to serial converter
that works properly, the pl2303 devices do not fit that category.

good luck,

greg k-h