Add Bumble as BLE backend

[JPHutchins]

https://google.github.io/bumble/index.html

Having multiple BLE backends available is comprised of a few steps:

1. Add HW unit tests that perform SMP BLE operations
2. Define the common protocol required for an SMP BLE transport
3. Implement the protocol with Bleak and confirm no regression
4. Implement the protocol with Bumble and add to the HW unit tests

HW that I currently have available for HW unit tests:

• nrf52dk 52832
• nrf52dk 52840
• adafruit feather nrf52840

I also have a Boradcom BCM2070 USB BLE dongle (Plugable brand) that would be a good candidate for testing Bumble.

Sadly HW tests cannot run in GitHub workflow because this is a public repo: https://docs.github.com/en/actions/hosting-your-own-runners/managing-self-hosted-runners/about-self-hosted-runners#self-hosted-runner-security

I'd love to find a way!

[vChavezB]

Hi @JPHutchins , Im not sure if this would be of interest but I added sometime ago support to use bumble with native posix in Zephyr. More specifically, I added an HCI TCP channel that allows an application (e.g. Android Emulator, Bleak, bumble) to communicate over a virtual channel.

This means that in theory some SMP BLE commands could be tested without hardware directly with Zephyr´s BLE SMP Transport. The limitation is that you need a linux host that is compiled with Bluetooth support (not possible with native github runners). For CI this means a dedicated machine.

[JPHutchins]

It seems not very likely, but my preferred approach will be to add Bumble as a backend for Bleak: https://github.com/hbldh/bleak/discussions/1588

[vChavezB]

that sounds like a nice approach as it would also allow to do integration tests without hardware!

[vChavezB]

Attached just a small test I did. Bumble controller over VHCI.

Perhaps not that practical as image management depends on MCUBoot which is not supported by native posix.

https://github.com/user-attachments/assets/a3aa19e5-e12e-4c7c-9857-a0a1371fc689

[JPHutchins]

Whoa, this is amazing! And you're 100% the GitHub runner can't run it?

[JPHutchins]

Evil question: could I host that VHCI myself and have the GitHub runner talk to remotely?

[vChavezB]

This is more or less the setup

graph LR
    A[Zephyr\nposix app] <-->|socket| B[Bumble\nController]<--> C[VHCI]<-->|Bluez dbus| D[Bleak]

And you're 100% the GitHub runner can't run it?

Yes, the github runner image (ubuntu) does not have the vhci linux module enabled. This requires that the kernel has enabled CONFIG_BT.

could I host that VHCI myself and have the GitHub runner talk to remotely?

As I understand it, the VHCI is just a file descriptor, so I think you could just add it as a remote service, perhaps accessible with github secrets. Then add a custom bumble transport so bumble can access it or instead just make the bumble controller remotely accessible.

graph LR
    subgraph Self-hosted vhci

        C[VHCI]
    end

    subgraph Runner
            D[Bleak]
            B[Bumble\nController]
        A[Zephyr\nposix app] 
    end

    A <-->|socket| B <--> |remote\nsocket| C
    D <-->|remote\nDBus ?| C

Edit: Just some minor changes on what I think could be done with non-self-hosted github runners.

But to be honest for practical reasons I would host my own runners (Gitlab, Github, etc).

[vChavezB]

Just another thought, perhaps for the HW runners you could just add a Web hook so your local server runs the test for a specific commit, then reports back the result. How the result is reported back is up to you.

[JPHutchins]

This is a good idea as it gives more control. Yet, the goal is for contributors to be able to run a suite of hardware integration tests, and that still opens me up to arbitrary code execution. Specifically, I want to run the hardware integration tests at the contributors' commit, and they could simply commit whatever they want so that Python runs something nasty on import.

There's the possibility of manual review + run, though. I'd only submit the HW integration workflow once it's clear that the commit is OK.

It's a good idea!