linux-kernel - Re: Regarding USB-to-serial device driver

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Date:	Thu, 23 Sep 2010 15:45:52 +0530
From:	"Raju Rameshwar Uprade" <rajsingh@...a.tifr.res.in>
To:	Greg KH <gregkh@...e.de>,
	Raju Rameshwar Uprade <rajsingh@...a.tifr.res.in>
Cc:	linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org
Subject: Re: Regarding USB-to-serial device driver

> For what driver?

  I am using pl2303.c ( USB to serial device driver ) to communicate to various devices
connected in parallel using RS-485 interface card.

> > Kindly help me.I am facing the problem in separating the data bytes so
> > that I can send the data bytes separately using usb_submit_urb.
> 
> It all depends on the driver you are using.  Why not do all of this from
> userspace?  That way it works on any device you are talking to.

I want to write data twice :

1. Only address byte and then 
2. Data bytes.

I am properly allocating memory for write_urb using kzalloc.When I write complete user
buffer to the port, it send the data properly.

But when I try to write only address byte machine get hang.

I have attached the source file.

Thanks,
 Raj.

View attachment "pl2303_mcm.c" of type "text/x-csrc" (34224 bytes)