Can we disable STDIO printf but keep DEVICE_SERIAL

[LMESTM]

Description

In https://github.com/ARMmbed/mbed-os/blob/master/platform/mbed_retarget.cpp#L277, as soon as DEVICE_SERIAL is supported, an STDIO serial will be created for printf support.

Could there be an option for disabling STDIO console and select SINK one instead, without disabling DEVICE_SERIAL which may be needed by peripherals drivers.

Could be something like:
#if (DEVICE_SERIAL && !MBED_CONF_PLATFORM_STDIO_SINK))

This could be useful when switching to release mode or to improve low power consumption.
Maybe there is already an alternative method that I am not aware of.

Issue request type

[x ] Question
[ ] Enhancement
[ ] Bug

[jeromecoutant]

In #5658 old issue, I thought it was DEVICE_STDIO_MESSAGES goal.
But I didn't get any clear answer...

[0xc0170]

cc @kjbracey-arm

[kjbracey]

I don't understand the intent of DEVICE_STDIO_MESSAGES either. Presumably it was supposed to be something like this, but I'd be inclined not to touch it, as I don't know who's using it.

If for power, as of 5.12, you can save power by suspending input, although that doesn't help your ROM space: #9797

I'd suggest a new option platform.stdio-serial which defaults to true, so it's #if MBED_CONF_PLATFORM_STDIO_SERIAL && DEVICE_SERIAL.

I'm reluctant to have a bunch of options for possible modes, as we already have a functional target override system I want people to use, but having an option to nix the default use-serial behaviour makes sense.

[LMESTM]

What I'm actually looking for is stdio_uart to not be initialized at all.

I'd suggest a new option platform.stdio-serial which defaults to true, so it's #if MBED_CONF_PLATFORM_STDIO_SERIAL && DEVICE_SERIAL.

So yes, that sounds good to me .

[ciarmcom]

Internal Jira reference: https://jira.arm.com/browse/MBOCUSTRIA-1122