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

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Message-ID: <20100923140236.GB31394@suse.de>
Date:	Thu, 23 Sep 2010 07:02:36 -0700
From:	Greg KH <gregkh@...e.de>
To:	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

On Thu, Sep 23, 2010 at 03:45:52PM +0530, Raju Rameshwar Uprade wrote:
> > 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.

So your program is going to fail if you use a different hardware device?
That doesn't sound like a good idea.

> > > 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.

Again, do this in userspace.

> 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.

Sorry, I really don't know, you are on your own here.

good luck,

greg k-h
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