STRUCT SCMI_REGISTERED_EVENTS_DESC(9)

💅 struct scmi_registered_events_desc(9) — Kernel API Manual 💅

okay so bestie, let me tell you about this struct. It's giving protocol-specific information and it's lowkey iconic. No cap.

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✨ NAME ✨

struct scmi_registered_events_desc — protocol-specific information. That's the whole vibe. It's literally the place where a protocol's event stuff lives, and we're obsessed.

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🦋 SYNOPSIS 🦋

struct scmi_registered_events_desc {
    u8 id;
    const struct scmi_event_ops     *ops;
    struct events_queue             equeue;
    struct scmi_notify_instance     *ni;
    struct scmi_event_header        *eh;
    size_t eh_sz;
    void *in_flight;
    int num_events;
    struct mutex                    registered_mtx;
    const struct scmi_protocol_handle       *ph;
    unsigned long registered_events_handlers[1 << ((
SCMI_REGISTERED_HASH_SZ) - 1)];
    struct scmi_registered_event    *registered_events[];
};

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🎀 Members 🎀

• id — the protocol ID. Like, which protocol even is this? That's what id tells you. No cap.
• ops — protocol-specific and event-related operations. The whole operations situation for this protocol's events.
• equeue — the embedded per-protocol events_queue. It's giving queue, but make it protocol-specific. Slay.
• ni — a reference to the initialized instance descriptor. The notification instance's main character energy.
• eh — a reference to a pre-allocated buffer that the deferred worker uses as a scratch area when fetching data from the kfifo. Lowkey essential for the fetch. iykyk
• eh_sz — the size of that pre-allocated buffer eh. Gotta know how much room you have.
• in_flight — a reference to an in-flight struct scmi_registered_event. It's in the air, it's happening, it's in flight.
• num_events — the number of events in registered_events. Like a headcount but for events.
• registered_mtx — a mutex that protects registered_events_handlers. Lock it down, bestie. 🔒
• ph — SCMI protocol handle reference. The whole protocol handle situation.
• registered_events_handlers — a hashtable (yes, the kernel says "hashtable", we respect it) containing all the events' handler descriptors that are registered for this protocol.
• registered_events — a dynamically allocated array holding all the registered events' descriptors. Its fixed size is determined at compile time — so like, set in stone before runtime even starts. periodt.

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🌸 Description 🌸

All protocols that register at least one event have their protocol-specific information stored here, together with the embedded allocated events_queue. These descriptors are stored in the registered_protocols array at protocol registration time.

And once these descriptors are successfully registered, they are NEVER again removed or modified — because protocols do not unregister ever. So once we safely grab a NON-NULL reference from the array, we can keep it and use it. Periodt. That's the whole point. ✨

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👑 SEE ALSO 👑

Bestie, if you wanna go deeper (and you should, iykyk), check out:

Kernel file ./drivers/firmware/arm_scmi/notify.c, Theory of operation(9), struct scmi_notify_instance(9), struct events_queue(9), struct scmi_event_header(9), struct scmi_registered_event(9), struct scmi_event_handler(9), scmi_lookup_and_call_event_chain(9), scmi_process_event_header(9), scmi_process_event_payload(9), scmi_events_dispatcher(9), scmi_notify(9), scmi_kfifo_free(9), scmi_initialize_events_queue(9), scmi_allocate_registered_events_desc(9), scmi_register_protocol_events(9), scmi_deregister_protocol_events(9), scmi_allocate_event_handler(9), scmi_free_event_handler(9), scmi_bind_event_handler(9), scmi_valid_pending_handler(9), scmi_register_event_handler(9), __scmi_event_handler_get_ops(9), scmi_get_active_handler(9), __scmi_enable_evt(9), scmi_put_handler_unlocked(9), scmi_event_handler_enable_events(9), scmi_notifier_register(9), scmi_notifier_unregister(9), scmi_devm_notifier_register(9), scmi_devm_notifier_unregister(9), scmi_protocols_late_init(9), scmi_notification_init(9), scmi_notification_quiesce(9), scmi_notification_exit(9).

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💖 That's the whole page, bestie. Source: ./drivers/firmware/arm_scmi · Version: struct scmi_..._events_desc(9) · Date: October 2026. Stay slay, and remember: once you grab that NON-NULL reference, you can keep it and use it. periodt. 💖