docs: surface the events-ringbuf-size-0 default in the README#37
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The events-ringbuf-size-{0..2048} features select the per-priority event
buffer size in `Events<N>`. The default of 0 silently no-ops every event
write in rs-matter's `EventWriter::write` (`dm/events.rs`):
if N == 0 { return Ok(()); }
`emit_event()` returns Ok, the subscription's `max_seen_event_number`
advances, but no bytes are ever stored and the controller never sees
event reports. The failure mode is subtle and easy to spend hours
chasing.
This affects any device that emits events, which is most of them:
Generic Switch (0x000F) is unusable without Switch cluster events, and
BasicInformation::StartUp on boot is required by Matter Core 1.5.1
§11.1.6. The Cargo.toml inline comment ("events will not be emitted")
understates the failure mode and isn't visible to anyone reading the
README.
Adds a short Event ring-buffer section with the gotcha, the fix, and
sizing guidance.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
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Hi again :)
Same gotcha I just pinged you about on
esp-idf-matter(sysgrok/esp-idf-matter#28), but documented on the side that actually owns the features.Burned a few hours debugging a Matter Generic Switch where
emit_eventreturnedOkandmax_seen_event_numberadvanced on every button press, yet the controller never received an event. Walking back throughrs-matter'sEventWriter::write:…lined up with the
events-ringbuf-size-0default. The `Cargo.toml` inline comment is accurate but invisible to anyone reading the README, and the failure mode is "everything looks fine, controller just sees nothing" — not the easiest to track down.Adds a short README section with the bit, the fix, and a sizing note. Wording is just a sketch.
An alternative (if it makes sense) would be to change the default to a non-zero size like 256 or 512, so devices that emit any event — today that's any cluster handler calling `emit_for`, plus rs-matter's own `AccessControlEntryChanged` event on ACL writes during commissioning — work out of the box, and only users explicitly disabling events would opt into 0.