On Wed, Feb 20, 2008 at 10:35:48AM -0800, Chetan Karia wrote:
> Hello,
> 
> I am kernel newbie and I have a question about usb serial driver. I
> have a usb to serial driver which exposes 3 virtual serial ports
> ttyUSB0, ttyUSB1 and ttyUSB2. The endpoint to virtual serial port
> mapping is like this
>          ep0 ==> ttyUSB0
>         ep1 ==> ttyUSB1
>         ep2 ==> ttyUSB2.

Which device is this?  I think you are talking about the endpoint
"pairs" one IN and one OUT per tty, right?

> All I want to do is create another virtual serial port ttyUSB3 (easy)
> and setup its endpoint address (bulk in and bulk out) to same as
> ttyUSB1 that is ep1. I do this in attach function of the driver and I
> want to know will there be any race condition if ttyUSB1 and ttyUSB3
> are used simultaneously? Is there any way to overcome that race
> condition or its simply not correct way to go.

Does the device really support another serial endpoint?  You can't just
make a new one if the hardware can't handle it.

> My sole intention for doing that is ttyUSB1 and ttyUSB3 should be able
> to read/write from/to same endpoint (ep1) concurrently. Is that
> possible?

Hm, why?  Some devices might get very confused, depending on the
protocol used by the device.  It all depends on the hardware.

What's wrong with just having 2 programs write to the same tty node at
the same time?

thanks,

greg k-h
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