Implement "Select devices" flow

[msirringhaus]

WIP as of now.

Looking how many devices are there on the start of an operation.
If one is there, just continue with that. If none are there, got to UsbState::Waiting as before.

If more than one are there, let each of them blink in it's own tokio-task and wait for user interaction. Once the user selects one, that operation returns with true, and we send that over a dedicated channel.
If the user does not select any device, we run into timeouts, count out how many timeouts we collected and if all starting devices are accounted for, stop the operation.

I'm not yet able to stop the blinking of all not-chosen devices, once the user has selected one, because I can't clone the hid-channel, and I can't have them in the UsbState-enum, because they are not clone-able.

[iinuwa]

I'm not yet able to stop the blinking of all not-chosen devices, once the user has selected one, because I can't clone the hid-channel, and I can't have them in the UsbState-enum, because they are not clone-able.

Have you tried wrapping the device/channel in Arc<Mutex<Option<HidDevice>>? That should allow access from multiple threads. You may need to use the Tokio version of Arc and Mutex if the lock is held across an await point to prevent deadlocks.

[iinuwa]

The happy path works well here: I'm able to select a specific device! If I unplug a device while in SelectingDevice state, the service crashes on https://github.com/msirringhaus/xdg-credentials-portal/blob/2350536d2e5433916c9d23efd82891dbc9366cea/libwebauthn/src/transport/hid/channel.rs#L267.

I'll create an issue over there for that.

I'm not yet able to stop the blinking of all not-chosen devices, once the user has selected one, because I can't clone the hid-channel, and I can't have them in the UsbState-enum, because they are not clone-able.

Is the above still true? For me, after selecting a device, the other one keeps blinking.

If that's expected, let's file this as a separate issue and call this one done.

[iinuwa]

Created linux-credentials/libwebauthn#103 for the panic on unplug issue

[iinuwa]

(Finally applied rustfmt to all the files; merged the conflicts back into your branch.)

[msirringhaus]

I'm not yet able to stop the blinking of all not-chosen devices, once the user has selected one, because I can't clone the hid-channel, and I can't have them in the UsbState-enum, because they are not clone-able.

Is the above still true? For me, after selecting a device, the other one keeps blinking.

If that's expected, let's file this as a separate issue and call this one done.

Yes, this is still true. The HidDevices are now cloneable, but not the channels. Additionally, libwebauthn doesn't yet have a cancel-function. This was going to be my next work item.
I hope that I can create a second channel from the cloned device and abort any ongoing operation on the hardware. But first, libwebauthn needs to implement CTAPHID_CANCEL

[iinuwa]

This looks good; let's leave the blink cancellation to another PR. Thanks!