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

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Message-ID: <20100922145607.GB26309@suse.de>
Date:	Wed, 22 Sep 2010 07:56:07 -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 Wed, Sep 22, 2010 at 11:02:46AM +0530, Raju Rameshwar Uprade wrote:
> 
> 
> Greg,
>       I am facing some problem in data copying.
> I am having a const unsigned char *buf which contains 02 08 00 00 00 00 00 00 f8.
> which is copied in port->write_urb->transfer_buffer and sent on ttyUSB0 using
> usb_submit_urb(port->write_urb, GFP_ATOMIC).

For what driver?

> But  I want to send the data bytes is a particular fashion.
> 
> 1. I want to Add Mark parity. 

That's a control signal and is independant of the data payload, right?

> 2. Send the data byte 02 ( Address of a device )

That means you need to modify the data.  Why not do that in userspace?

> 3. Add Space parity .

Again, control signal.

> 4. send the data byte 08 00 00 00 00 00 00 f8 ( Null cmd + check sum )

Should be fine.

> 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.

good luck,

greg k-h
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