type-c-interface: Add notification traits

[RobertZ2011]

Add notification traits to allow services to decouple from the notion of a channel-like object. This makes our code more flexible and makes it easier to implement certain types of custom functionality.

assisted-by:claude-opus-4.8

[Copilot]

Pull request overview

This PR introduces notification traits in type-c-interface to decouple Type-C components from a concrete “channel sender” abstraction, enabling alternative notification backends (blocking vs non-blocking) while keeping call sites consistent. It updates type-c-service to depend on these notifier traits for both per-port events and service-wide events (e.g., debug accessory, UCSI connector change). It also updates tests and examples to wrap existing channel senders in notifier adapters via .into(), preserving existing behavior while making the wiring more flexible.

Changes:

• Add type_c_interface::{port,service}::notification::{Notifier, Error} traits and errors, plus adapter newtypes that implement Notifier for Sender/NonBlockingSender.
• Refactor type-c-service registration and event emission paths to use notifier traits instead of directly calling try_send on channels.
• Update tests/examples/macros to wrap existing senders into notifiers (NonBlockingSenderNotifier).

Step-by-step Review Guide

1. New notification traits (interface-level)

   • Review type-c-interface/src/service/notification.rs and type-c-interface/src/port/notification.rs for the intended contract (backpressure signaling vs blocking behavior).
   • Review the adapter implementations in type-c-interface/src/service/event.rs and type-c-interface/src/port/event.rs:
     • NonBlockingSenderNotifier maps try_send failure to Error::WouldBlock.
     • SenderNotifier awaits send and currently always returns Ok(()), which can introduce blocking semantics.

2. Service refactor to call notifiers

   • Review type-c-service/src/service/registration.rs to confirm the service now registers ServiceNotifier types rather than event senders.
   • Review type-c-service/src/service/mod.rs where the service calls notifier methods inline while processing events, and note the impact if any notifier implementation blocks.

3. Controller refactor (per-port notifications)

   • Review type-c-service/src/controller/mod.rs and related controller trait impls (pd.rs, power.rs, etc.) to see that the per-port “type-c sender” becomes a PortNotifier.
   • Confirm the semantics of previously non-blocking try_send sites now depend on which notifier adapter is used.

4. Tests/examples wiring

   • Review the test/common and examples changes to ensure they consistently wrap existing senders into NonBlockingSenderNotifier via .into(), maintaining non-blocking behavior.

Potential Issues

#	Severity	File	Description	Code
1	🔴 High	type-c-service/src/service/mod.rs:80-95	Service awaits each notifier inline; using the new blocking SenderNotifier adapters can stall the service event loop under backpressure. Consider constraining registrations to non-blocking notifiers or isolating blocking listeners behind a task/queue boundary.	for notifier in self.registration.notifiers() { ... .await ... }
2	🟡 Medium	type-c-interface/src/service/notification.rs:16-17	Public notifier trait doesn’t document whether notify_* futures may block; this is important because call sites may be time-sensitive.	pub trait Notifier<'port> { ... -> impl Future ... }
3	🟡 Medium	type-c-interface/src/port/notification.rs:19-20	Same contract ambiguity for port notifications; blocking implementations can add latency/stall controller/state-machine paths.	pub trait Notifier { ... -> impl Future ... }

Reviewed changes

Copilot reviewed 22 out of 22 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
type-c-service/tests/common/mod.rs	Switch test wiring to wrap port/service senders into notifier adapters.
type-c-service/src/service/ucsi.rs	Route UCSI change indicator emission through the new service notifier API.
type-c-service/src/service/registration.rs	Refactor registration from event senders to service notifiers.
type-c-service/src/service/mod.rs	Replace broadcast-event cloning with notifier calls; implement NotificationHandler.
type-c-service/src/controller/ucsi.rs	Update controller port generic parameter from sender to port notifier.
type-c-service/src/controller/type_c.rs	Update controller port generic parameter from sender to port notifier.
type-c-service/src/controller/retimer.rs	Update controller port generic parameter from sender to port notifier.
type-c-service/src/controller/power.rs	Update controller port generic parameter from sender to port notifier; notify via notifier.
type-c-service/src/controller/pd.rs	Send VDM/DP-status/alert notifications via PortNotifier instead of try_send.
type-c-service/src/controller/mod.rs	Rename stored sender field to notifier and notify status-changed via notifier.
type-c-service/src/controller/max_sink_voltage.rs	Update controller port generic parameter from sender to port notifier.
type-c-service/src/controller/macros.rs	Provide notifier type aliases and wrap senders into notifiers in macro expansion.
type-c-service/src/controller/electrical_disconnect.rs	Update controller port generic parameter from sender to port notifier.
type-c-interface/src/service/notification.rs	Add service notification trait + error type (new file).
type-c-interface/src/service/mod.rs	Export the new service::notification module.
type-c-interface/src/service/event.rs	Add service notifier adapter newtypes for Sender/NonBlockingSender.
type-c-interface/src/port/notification.rs	Add port notification + handler traits and error type (new file).
type-c-interface/src/port/mod.rs	Export the new port::notification module.
type-c-interface/src/port/event.rs	Add port notifier adapter newtypes for Sender/NonBlockingSender.
examples/std/src/lib/type_c/mock_controller.rs	Update mock controller port type to use port notifier adapter.
examples/rt685s-evk/src/bin/type_c.rs	Update example wiring to register service notifiers and port notifiers.
examples/rt685s-evk/src/bin/type_c_cfu.rs	Update CFU example wiring to register service notifiers and port notifiers.