On Mon, Feb 25, 2008 at 03:44:19PM -0800, Kevin Lloyd wrote:
> > > The sierra device has pair of endpoints (bulk in and bulk out)  that
> > > sends the multiplexed protocols data packets ( two protocols data
> > > packets encapsulated in one). Lets call that endpoint pair as EP1.
> The
> > > one of the multiplexed protocol is DM and other is command and
> status.
> > > EP1 is attached to ttyUSB1. Our application reads from ttyUSB1 and
> > > ignores DM packets and considers only command and status packets.
> > > However to get DM stream working another application has to
> read/write
> > > to ttyUSB1 concurrently which is as tricky. Thus, I am trying to
> setup
> > > another virtual serial port called ttyUSB3 that can read/write to
> EP1
> > > concurrently so that we get two duplicate streams. One of the stream
> > > (ttyUSB1) can be used by our existing application and another stream
> > > (ttyUSB3) can be used to set up DM logging.Internally however they
> > > will talk to same endpoint pair EP1. Is it doable?
> > 
> > Yes, for something like this, a modification of the sierra driver
> would
> > be needed to allow for two buffers like this.
> > 
> > But, you might want to work with the current developers of the sierra
> > driver, as I'm pretty sure they are working to add this kind of
> > functionality (alternate ways to control the card) to the driver for
> > this very reason.
> > 
> > Is there a reason you have not just contacted them already?
> Hi Greg et al.,
> 
> Chetan is actually helping Sierra out with this feature and I was not
> able to be of much help regarding finding a solution in the kernel
> space.

Then please, let us know this kind of information in the beginning,
without me having to drag it out of you all over the course of a week
and 9 email exchanges.  Don't be vague, it doesn't help anyone out, and
wastes people's time.

> I saw that the network driver framework has the ability to register
> packet handlers to devices data streams via the dev_add_pack command, I
> was hoping that the usb_serial drivers might have similar functionality
> (I couldn't find any).

No, the tty layer doesn't let you do this.  Well, it could, if you
create a new line discipline, but I really think you don't want to do
that, it's quite difficult.

Why not just use what Alan suggested?  Do all of this logic in a
userspace program?

thanks,

greg k-h
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