Date: Fri, 8 Oct 2021 10:58:40 +0300 From: Mehmet Erol Sanliturk <m.e.sanliturk@gmail.com> To: Milan Obuch <freebsd-hackers@dino.sk> Cc: FreeBSD Hackers <freebsd-hackers@freebsd.org> Subject: Re: Persistent USB serial? Message-ID: <CAOgwaMvNbWRpXhBkEDU4wChjF_TkDE6OX4%2BWB6FHncTBDK4GNA@mail.gmail.com> In-Reply-To: <20211008080016.7830e3d5@zeta.dino.sk> References: <20211008080016.7830e3d5@zeta.dino.sk>
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--00000000000076f57505cdd2c14c Content-Type: text/plain; charset="UTF-8" On Fri, Oct 8, 2021 at 9:01 AM Milan Obuch <freebsd-hackers@dino.sk> 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 > > I am not using the following idea , but my opinion on that case is as follows : Assume that there is a list of ports to be defined such as USB , PCI , RS-232 , etc . If the board is a new one ( Boot the computer and obtain the above list . Make it a configuration file with ASSIGNED suitable port numbers by the user . ) otherwise use a previously prepared configuration . When the computer starts to boot , it looks at the above file . If it is present , ( without fancy mount operations by the user ) loads it and uses port numbersspecified in the given list . If it is not present , the computer uses its own defaults . In case of specified port numbers ( or names , labeling is not important ) , it uses giving numbers , causing repeatable boot sequences and the related scripts , etc. can continue as specified without being broken . Perhaps , such an application requires some changes in the boot processing sources which these are beyond my knowledge . Mehmet Erol Sanliturk --00000000000076f57505cdd2c14c--
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