USB serial ports by serial number

[O'Connor, Daniel]

> On 3 Oct 2019, at 17:41, Hans Petter Selasky <hps at selasky.org> wrote:
> 
> On 2019-10-03 09:37, O'Connor, Daniel wrote:
>>> On 3 Oct 2019, at 17:01, Hans Petter Selasky <hps at selasky.org> wrote:
>>> On 2019-10-03 08:56, O'Connor, Daniel wrote:
>>>> Most of USB-serial devices have "very stable" serial number:)
>>>> more than 50% have S/N "0123456789".
>>> 
>>> It is also allowed to have no serial number.
>> Yes, that's why I match sernum to '.+' to skip those.
>>> Maybe some kind of "lstty" would do.
>>> 
>>> -l  -  list all devices
>>> -s  -  match by serial
>>> -v  -  match by vendor
>>> -p  -  match by product
>>> -i  -  match by interface ID
>>> -t  -  type [USB/PCI]
>>> 
>>> which simply output the tty number you need. Could be an API we could add to libusb.
>> The problem is you can't modify some program to call a new API a lot of the time but it is usually trivial to change which serial port it's configured to use.
> 
> You don't need to change any program:
> 
> cu /dev/cuaU`lstty -s SERIAL`

That doesn't work in a lot of cases, eg serial port is in some other configuration file.

Even in rc.conf it would be tricky since that file is read so often.

--
Daniel O'Connor
"The nice thing about standards is that there
are so many of them to choose from."
 -- Andrew Tanenbaum