Date: Thu, 27 Aug 2015 09:37:59 +0200
From: Johan Hovold <johan@kernel.org>
To: Ajay Garg <ajaygargnsit@gmail.com>
Cc: Johan Hovold <johan@kernel.org>, Peter Stuge <peter@stuge.se>,
        linux-kernel@vger.kernel.org, linux-usb@vger.kernel.org
Subject: Re: Likely issue with ch341 kernel-module/driver
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[ Please avoid top-posting. ]

On Thu, Aug 27, 2015 at 12:13:32PM +0530, Ajay Garg wrote:
> I started in the morning to build the driver from the source provided
> by the vendor, but it was written in the times of kernel-version 2.4,
> and I got hopelessly stuck.

The vendor driver is only for 2.4? Peter?

> Wanting to take a break, I reset my setup, and VERY strangely, what I
> now observe is ::
> 
> a)
> I am NOT able to send anything from the embedded-system to
> putty-session (nothing appears at all on the putty session).
> 
> b)
> Receive is working perfectly (anything I type in the putty-session is
> received fine in the embedded-application).
> 
> 
> Not sure what the hell is going on :(

Did you enable hardware flow control somewhere perhaps?

> Also, as per http://lxr.free-electrons.com/source/drivers/usb/serial/ch341.c?v=3.16,
> the particular serial-USB-adapter device is added into the id_table,
> so seems supported as per say.

That id was added by 82078234d402 ("USB: serial: ch341: New VID/PID for
CH341 USB-serial") in 2008, which claims that the driver supports both
old and new devices.

> Additionally, the message has changed to
> 
> ###########################################################
> usb 2-2: device not accepting address 8, error -71
> ###########################################################

This still looks like a hardware issue to me. Specifically, this happens
before the ch341 driver is even involved.

> Completely lost :(

Try to see if you can get the device to work reliably with some other
driver (vendor driver or other OS) to rule out a broken device. 

Thanks,
Johan
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