rtc_read_next_alarm(9)

💖 rtc_read_next_alarm(9) 💖

okay so this is a page straight out of the Kernel API Manual — it's rtc_read_next_alarm(9), bestie, and it's genuinely one of the more useful little gremlins in the RTC toolbox. let's get into it 🕰️✨

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✨ NAME ✨

rtc_read_next_alarm — read the next expiring alarm 🔔

like, the alarm that's actually gonna go off next. not the one you think is next. the real one. iykyk.

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🌸 SYNOPSIS 🌸

int rtc_read_next_alarm (struct rtc_device *rtc , struct rtc_wkalrm
*alarm );

that's the whole signature, no cap — it takes two pointers and hands you back an int. 🫶

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🎀 ARGUMENTS 🎀

• rtc — the RTC device 🌈 (your real-time clock, the literal main character here)
• alarm — storage for the alarm information 🍓 (this is where the answer lands, so pls make sure it points somewhere valid)

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💅 DESCRIPTION 💅

so the way that this works: it reads the next expiring alarm from the RTC timerqueue. that's it, that's the vibe. ⏰

the important lil twist? it returns the alarm that will actually fire next, which — and this is the part that gets people — may be different from rtc_read_alarm if multiple timers are queued. the page literally calls out the example for you: like when alarmtimer and wakealarm sysfs are both active. 😭 two timers, one queue, and you wanna know which one's up first — that's this function, fr fr.

not me needing to re-read this three times the first time i saw it — the "may be different" thing is the entire personality of this function, don't skip it 🙈

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🔥 RETURN 🔥

• 0 — success, we ate 💖
• -ENOENT — no alarm is pending, so like… nothing's queued, bestie, go home 🫠
• or other error — because of course there could be other errors, it's kernel code 💀

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👑 SEE ALSO 👑

kernel file ./drivers/rtc/interface.c, plus the whole friend group:

• rtc_handle_legacy_irq(9)
• rtc_aie_update_irq(9)
• rtc_uie_update_irq(9)
• rtc_pie_update_irq(9)
• rtc_update_irq(9)
• rtc_irq_set_state(9)
• rtc_irq_set_freq(9)
• rtc_timer_enqueue(9)
• rtc_timer_remove(9)
• rtc_timer_do_work(9)
• rtc_read_offset(9)
• rtc_set_offset(9)

go read the whole squad, they're all iconic in their own way 🌟

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⭐ tiny sign-off: this lil page lives in ./drivers/rtc and it's dated October 2026 — so yeah, it's giving slightly-from-the-future energy 👑💜 go forth and read your next expiring alarm correctly, bestie 💅✨