native_posix: No support for "pull-model console"

[pfalcon]

"UART" is the default implementation console handler for Zephyr. Currently, building any sample in samples/subsys/console/ for BOARD=native_posix fails:

samples/subsys/console/echo:

/home/pfalcon/projects-3rdparty/Embedded/Zephyr/zephyr/subsys/console/getchar.c: In function ‘console_init’:
/home/pfalcon/projects-3rdparty/Embedded/Zephyr/zephyr/subsys/console/getchar.c:116:32: error: ‘CONFIG_UART_CONSOLE_ON_DEV_NAME’ undeclared (first use in this function)
  uart_dev = device_get_binding(CONFIG_UART_CONSOLE_ON_DEV_NAME);

samples/subsys/console/getchar:

/home/pfalcon/projects-3rdparty/Embedded/Zephyr/zephyr/subsys/console/getchar.c: In function ‘console_init’:
/home/pfalcon/projects-3rdparty/Embedded/Zephyr/zephyr/subsys/console/getchar.c:116:32: error: ‘CONFIG_UART_CONSOLE_ON_DEV_NAME’ undeclared (first use in this function)
  uart_dev = device_get_binding(CONFIG_UART_CONSOLE_ON_DEV_NAME);
                                ^

It would be nice to get that working (and shouldn't be too hard - this "uart console" would just proxy reads/writes from POSIX console).

[pfalcon]

@aescolar-ot: Can you please look at this?

This got to be related to #5861, if you got shell working, that you must have got console working first, so I'm going to try/look into that patch next.

[pfalcon]

So, the immediate problem here isn't "UART console" emulation, but that there's no "pull console" support for native_port. Proposed patch is posted as #5947

[galak]

Is this still relevant?

[pfalcon]

Yes, still relevant. However, recent console/tty patches may offer an alternative way to implement it for native_posix, simply bypass UART layer. But low priority, not sure that work fits in 1.14 timeframe.

Ref #10512, which discusses that console should work with other underlying devices besides UART.

[aescolar]

This is really a new feature/enhancement request, not a bug. Also not too high priority.
My understanding:
This subsys/console, how it is built now, it works only with a UART as backend, and only with those that support CONFIG_UART_INTERRUPT_DRIVEN
The UART driver for native_posix was just the minimum to get the new shell subsystem working (so no UART_INTERRUPT_DRIVEN support).
One possible solution is to add that support to the native_posix UART driver. That should also enable other use cases for the UART in native_posix. But doing this, does not just take 30 minutes.
Another option would be to change this subsys/console to not assume a UART as backend, and build a very slim backend for native_posix that just plugs to the host getchar. This would probably be faster and easier.
=> I unassign myself. If somebody has the time/will to take it they can.