Re: GPS hardware and TTYs

On 23.07.2019 11:56, Theo de Raadt wrote:

> Scott Seekamp <complists@risei.net> wrote:
>
>> I purchased an inexpensive USB GPS receiver to test with time keeping on
>> my OpenBSD 6.5 box. It's a "u-blox" supported by the nmea driver.
>>
>> Following the man pages for ldattach it says:
>>
>> "Specifies the name of the serial line. device should be a string of the
>> form "cuaXX" or "/dev/cuaXX".
>>
>> cua(4) [1] devices should be used when ldattach is started from the
>> command line; when started using init(8) [2], tty(4) [3] devices should
>> be used."
>>
>> However, if I use ttyU0 as the device in /etc/ttys I never get the
>> hw.sensors.nmea0 tree created. If I manually start ldattach with cuaU0
>> or put cuaU0 in /etc/ttys everything behaves as expected.
>
> There should never be cua devices in /etc/ttys, so something is curiously
> wrong.
>
> Can you try playing with some of the following flags, and tell us
> which ones work, from ttys(4):
>
> Additionally, the following flags modify the default behavior of the
> terminal line. Some of these flags may not be supported by a terminal
> line driver. The flag fields should not be quoted.
>
> local Treat the line as if it is locally connected.
>
> rtscts Use RTS/CTS hardware flow control, if possible.
>
> mdmbuf Use DTR/DCD flow control if possible.
>
> softcar Ignore hardware carrier on the line.
>
> Try all. Some of them will have similar effects.

I tested by:

- unplugging the sensor

- changing /etc/ttys

- kill -HUP 1

- plugging sensor in and waiting 30 seconds

- check sysctl output for data

No difference in behavior with any of the flags above. Dmesg output of
the device is:

umodem0 at uhub0 port 3 configuration 1 interface 0 "u-blox AG -
www.u-blox.com u-blox GNSS receiver" rev 1.10/3.01 addr 3

umodem0: data interface 1, has CM over data, has no break

umodem0: status change notification available

ucom0 at umodem0

I know I'm not telling you anything you don't already know, but
according to the ttys manpage:

> Whereas the dial-in device (the tty) normally requires a hardware signal to indicate to the system that it is active, the dial-out device (the cua) does not, and hence can communicate unimpeded with a device such as a modem, or with another system over a serial link.

Is it possible the sensor doesn't behave properly to tell the system
it's ready?

Thanks for the help!

Scott