On 2009-07-02, Manuel Jander <manuel.jander@xxxxxxxxx> wrote: > hopefuly this message is going to the right people. I wrote a > small virtual serial loop back driver and I have some > questions in regard to that. > > First, the driver basically creates a set of serial port > device pairs (/dev/ttySL0, /dev/ttySL1, etc) and if some > programs talks to one of this ports, the counterpart port will > receive all data and vice versa. Interesting. Does your driver live in the layer below the line-discipline layer, or is it a "from-scratch" character device driver? Are changes in termios settings (e.g. parity, buad, flow, etc.) reflected between the two devices? How does it handle modem-control/status lines? > This is usful for writing a simulator of a hardware device > which has a serial port, without having to connect to real > serial ports together with a null modem cable or something > like that. I'm using to develop a simulator of Webasto W-Bus > (ODB-II) car heating device. The driver can optionally do line > echo, required for K-Line emulation. > > Now the questions: > > - Did I really need to write a driver like this or are there > any trivial tricks to accomplish this somehow else? Without looking at the details of your driver, it's hard to say. For some applications that expect to talk to a serial port, you can use a pty pair. However, a pty only implements a subset of the serial port API Some applications that work with normal serial ports will fail if you point them at a pty instead of a "real" tty device. > Note, that the software to talk to my simulator is a > propietary windows executable (using wine), thus I can not > modify it. And my computer has only one single serial port > (and I would need to buy a second ODB-II hardware adapter > anyway, software is way much cheaper). > > - Is this useful to anyone ? I think it is :) and it would be > kind of stupid if anyone requiring this would have to either > use 2 hardware ports or write another driver like this. But > maybe I'm wrong, I dont know. > > - Is this driver worth to be part of the Linux mainline tree ? > Probably some adjustment would be required... On a couple occasions I offered (if it would be accepted) to fix up the pty driver so that it implements more of the serial port API, but I've never gotten any response. > source code is available here: > http://micro.homelinux.net/~mjander/serial_loop.zip Dude, a zip file? That ruined your Unix street cred. ;) > It did built on 2.6.28, hopefuly it also does on the current > vanilla tree. -- Grant Edwards grante Yow! ... I want a COLOR at T.V. and a VIBRATING BED!!! visi.com -- To unsubscribe from this list: send the line "unsubscribe linux-serial" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
