cdns_i2c_clk_notifier_cb(9)

✨ cdns_i2c_clk_notifier_cb ✨

okay so this is a page out of the Kernel API Manual and bestie, it's literally the glow-up story of a clock callback. buckle up 💅

---

🌸 NAME 🌸

cdns_i2c_clk_notifier_cb — the clock rate change callback, aka the function that gets the "hey, our clock just changed" text and has to decide if it's gonna be chill about it or not 🫶

---

🎀 SYNOPSIS 🎀

int cdns_i2c_clk_notifier_cb (struct notifier_block *nb , unsigned long
event , void *data );

---

🦋 ARGUMENTS 🦋

• nb — pointer to the notifier block. yeah, the standard notifier-block situation, you know the vibe 💫
• event — the notification reason. this is why you're being summoned, bestie, read it carefully 👀
• data — pointer to the notification data object. all the juicy details live in here 🍓

---

💖 DESCRIPTION 💖

so the way this works: this function gets called whenever the cdns_i2c input clock frequency changes — like, the clock is going through something and you're the main character who has to react 😭

the callback does a vibe check: it checks whether a valid bus frequency can actually be generated after the change. super reasonable of it, honestly.

• if yes → the change is acknowledged ✅ slay
• if no → the change is aborted ❌ absolutely not, we're not doing that today

and then, the new dividers get written to the HW in the pre- or post change notification, depending on which direction the scaling is going 👑 (pre for one direction, post for the other, iykyk — it's giving "the order matters" energy)

---

🔥 RETURN 🔥

• NOTIFY_STOP — the rate change should be aborted. nope nope nope, shut it down 💀
• NOTIFY_OK — acknowledge the change. yes bestie, we're doing this, approved ✨
• NOTIFY_DONE — the notification is considered irrelevant. not my problem, not my business, moving on 🙈

---

🌈 SEE ALSO 🌈

the kernel file it all lives in: ./drivers/i2c/busses/i2c-cadence.c — go read it, it's iconic 📖

and the whole friend group of related things:

• enum cdns_i2c_mode(9)
• enum cdns_i2c_slave_state(9)
• struct cdns_i2c(9)
• cdns_i2c_init(9)
• cdns_i2c_runtime_suspend(9)
• cdns_i2c_runtime_resume(9)
• cdns_i2c_clear_bus_hold(9)
• cdns_i2c_slave_isr(9)
• cdns_i2c_master_isr(9)
• cdns_i2c_isr(9)
• cdns_i2c_mrecv(9)
• cdns_i2c_msend(9)
• cdns_i2c_master_reset(9)
• cdns_i2c_master_xfer(9)
• cdns_i2c_master_xfer_atomic(9)
• cdns_i2c_func(9)
• cdns_i2c_calc_divs(9)
• cdns_i2c_setclk(9)
• cdns_i2c_detect_transfer_size(9)
• cdns_i2c_probe(9)
• cdns_i2c_remove(9)
• cdns_i2c_shutdown(9)

---

ok that's the whole page, no cap, every single detail is there 💜 go forth and handle your clock notifications responsibly

and that's a wrap bestie 🎀 this one's straight out of ./drivers/i2c/busses, dated October 2026 — catch you on the next page ✨💅🦋