Greentea client isn't outputting to the console

[kjbracey]

Note: This is just a template, so feel free to use/remove the unnecessary things

Description

• Type: Enhancement
• Related issue: Enable flow control in Greentea #6660
• Priority: Minor

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Enhancement

Greentea client is unnecessarily tied to RawSerial, potentially limiting performance, and preventing its use over any other comms interface. It's also causing configuration complications with tracking the serial port settings specified for the stdout console, as illustrated by #6660.

It's apparently avoiding the simplest printf and putc to permit use from interrupt (ARMmbed/greentea-client@ff62371).

This can be now be achieved in a more elegant and portable fashion using write(STDOUT_FILENO) - this will in principle work from interrupt, subject to limitations of the FileHandle being used for the console. It will currently work with the default non-buffered console, equivalent to RawSerial.

A little more discussion in comments on #6660

[0xc0170]

@SenRamakri @bulislaw Please review

It's apparently avoiding the simplest printf and putc to permit use from interrupt (ARMmbed/greentea-client@ff62371).

cc @adbridge I checked the original addition to greentea to start using RawSerial done by you so might be interested in this.
[Mirrored to Jira]

[adbridge]

@theotherjimmy You may want to take a look too as this falls under your remit now.
[Mirrored to Jira]

[kjbracey]

I am curious why you're trying to output from interrupt context. Yes, you can use RawSerial or write(STDOUT_FILENO) to do that, but doesn't mean you should.

I'm advocating use of write(STDERR_FILENO) to get fault, assert and other "die" handlers to send stuff to arbitrary console, removing their serial dependency (should probably raise an issue to track that if there isn't one).

But holding up a running system in IRQ context to wait for the serial port is a different issue. More than 1 character at 115200 blows the 100us IRQ latency that is usually a good guideline. I guess as long as it's just test code, or the IRQ messages are teeny?

[Mirrored to Jira]

[theotherjimmy]

@adbridge This is not under my remit. I maintain the greentea host side of things.
[Mirrored to Jira]

[adbridge]

Internal Jira reference: https://jira.arm.com/browse/IOTCORE-336

[ciarmcom]

Thank you for raising this issue. Please note we have updated our policies and
now only defects should be raised directly in GitHub. Going forward questions and
enhancements will be considered in our forums, https://forums.mbed.com/ . If this
issue is still relevant please re-raise it there.
This GitHub issue will now be closed.