Date: Fri, 8 Oct 2021 09:34:13 +0200 From: Milan Obuch <freebsd-hackers@dino.sk> To: freebsd-hackers@freebsd.org Subject: Re: Persistent USB serial? Message-ID: <20211008093413.19e7acd2@zeta.dino.sk> In-Reply-To: <20211008072537.vytjzyqol5cksy5d@nerd-thinkpad.local> References: <20211008080016.7830e3d5@zeta.dino.sk> <20211008072537.vytjzyqol5cksy5d@nerd-thinkpad.local>
next in thread | previous in thread | raw e-mail | index | archive | help
On Fri, 8 Oct 2021 09:25:37 +0200 Daniel Ebdrup Jensen <debdrup@FreeBSD.org> wrote: > On Fri, Oct 08, 2021 at 08:00:16AM +0200, Milan Obuch wrote: > >Hi, > > > >I'd like to solicit opinions/hints for following scenario, which is > >quite common currently. > > > >There are some development and evaluation boards designed with USB > >port as power source and serial console at the same time (sometimes > >even more ports or JTAG as well). When board has power on switch, > >usually no activity is present on USB wire without board being > >powered - there is some USB-to-UART circuitry powered from board > >power source. So serial port device /dev/cuaUn et al. get created > >only after power on of the board. > > > >Problem: port number can be different depending on USB port > >enumeration or connection order. Another one: it is easy to miss > >first characters sent from the board if you are not able to write > >required command like 'cu -l /dev/cuaU9 -s 115200' quickly. > > > >Maybe it is possible to write some devd config file snippet which > >ensures consistent device naming without need of maintaining correct > >(everytime the same) order of cable connecting, but even that, this > >does not solve second problem, starting up some terminal or terminal > >like program in time. > > > >Has anybody some experience in this area who can share it? Some hints > >what to test? Do we have some pseudo serial device, which can be used > >as device argument for cu command, which can just grab the real USB > >serial when it appears on connecting the board under test? > > > >Regards, > >Milan > > > > Hi Milan, > > There's an open review [1] for location-based unit numbering for USB, > which some of us have been using for quite some time - and while it's > not completely done, it's very useful. > > Yours, > Daniel Ebdrup Jensen > > 1: https://reviews.freebsd.org/D21886 Thanks for pointer, I'll try to evaluate. This does not give me a full solution, if I understand it right - I can have some unique name for a given USB serial port instance, but I still must write my command to attach to this port quickly in order to not miss first characters sent over this port, right? Regards, Milan
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?20211008093413.19e7acd2>