On Mon, May 22, 2017 at 07:16:17PM +0100, Alan Cox wrote: > > disconnect frame before initialising multiplex mode. Since it's not so > > nice that userspace has to know the layout of a disconnect frame, > > the second patch introduces a disconnect ioctl which can be issued > > right before closing the physical port during the first session. > > This ioctl is only useful when during the second session it is known > > the the first session has been closed properly, so I'm not sure > > how useful it is to introduce such an ioctl. > > I don't think it justifies an ioctl and the likely use case is that the > tty is hung up when the process dies so would already be in N_TTY at the > point anyone tried to clean up.
Ok, so let's drop the second patch. > > A more interesting question - and I don't have enough hardware to test > this any more - would be whether we can safely send that sequence if our > initial connects failed a few times so we try disconnect/reconnect. In my current userspace test program I now unconditionally send the sequence right before sending the AT+CMUX command. This works fine, no matter if the modem was still in CMUX mode or not. I can only speak for a UBLOX modem though, other modems might behave differently here. For example my UBLOX needs the CLD message to close down the multiplexer, just closing DLC0 does not work. Sascha -- Pengutronix e.K. | | Industrial Linux Solutions | http://www.pengutronix.de/ | Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |
