k20: Introduce app_blink_k20_isr.

[dpc]

No description provided.

[bharrisau]

Interrupts are still a bit ugly at the moment.

Could you try moving the WFI instruction to the lib::support module? I've been meaning to create functions for all the 'extra' ASM instructions supported by the devices.

[dpc]

I will move wfi to support, OK.

I actually found it surprisingly easy to plug-in my own ISR. I wasn't aware on the way Cortex-Mx handle exception, coming from Cortex-Ax.

What I'm unsure about is what is agreed on approach of handling global values from ISR. System-level Rust has some strong guarantees on aliasing, which ISR obviously break by definition. It's still not that hard, comparing to what should be done in case of SMP...

[dpc]

r?

[farcaller]

LGTM as a proof of concept, but we must get rid of this later on. I don't see how can we communicate from ISR to task code without globals, so we need to limit the code to minimal possible. The best case — top half is generated implicitly in PT and talks to bottom half with optional user-managed code via some queue.

[bharrisau]

Sorry - you'll need to rebase this as I moved some stuff around.

[dpc]

Done.

[bharrisau]

I was thinking something similar to a queue too. Push notifications in from interrupts, pull out from the main loop. Would need to be threadsafe to prevent a pre-mpted interrupt from ruining something.

[bharrisau]

Thanks for this.