spi_bus_unlock(9)

💅 spi_bus_unlock(9) — the Kernel API Manual glow-up

okay bestie, so this is a page from the Kernel API Manual about spi_bus_unlock(9), and honestly? It's a short one but she's iconic in her simplicity. Let's get into it ✨

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🌸 NAME 🌸

spi_bus_unlock — release the lock for exclusive SPI bus usage 🎀

Like, you grabbed the aux cord, and now you're giving it back. Manners. We love to see it.

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✨ SYNOPSIS ✨

int spi_bus_unlock (struct spi_controller *ctlr );

That's it. That's the whole vibe. One function, one argument, one int coming back at you 💖

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🫶 ARGUMENTS 🫶

• ctlr — the SPI bus controller that was locked for exclusive bus access. yes queen, that one, the same controller you locked before. no switchesies 🔒

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😴 CONTEXT 😴

can sleep

fr fr, this one is allowed to snooze. she's not in a rush, she's not in an interrupt, she's just vibing in a context that's permitted to sleep 💤

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👑 DESCRIPTION 👑

Okay so here's the tea 🍓: this call may only be used from a context that may sleep. That's non-negotiable, bestie — don't try to sneak it into an atomic context, it's giving "read the room".

And just so you know exactly what kind of nap we're talking about: the sleep is non-interruptible, and it has no timeout. Not "sleep until someone pokes you", not "sleep for a bit then give up" — it's the committed, all-in kind of sleep. main character energy ngl 😭

What this call actually does: it releases an SPI bus lock previously obtained by an spi_bus_lock call. So the lock has to already exist — you're the one undoing it, not creating it 🔓

⚠️ don't call this without having called spi_bus_lock first, okay? that's not a lock release, that's just chaos 💀

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🔥 RETURN 🔥

always zero.

always. zero. every single time. no cap. she does not have a failure mode, she does not have opinions, she simply returns 0 and walks away 💅✨

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🌈 SEE ALSO 🌈

aaaand here's the whole friend group 🫶 — all from the kernel file ./drivers/spi/spi.c:

• __spi_register_driver(9)
• spi_alloc_device(9)
• spi_add_device(9)
• spi_new_device(9)
• spi_unregister_device(9)
• spi_register_board_info(9)
• spi_res_alloc(9)
• spi_res_free(9)
• spi_res_add(9)
• spi_res_release(9)
• spi_finalize_current_transfer(9)
• __spi_pump_messages(9)
• spi_pump_messages(9)
• spi_take_timestamp_pre(9)
• spi_take_timestamp_post(9)
• spi_set_thread_rt(9)
• spi_get_next_queued_message(9)
• spi_finalize_current_message(9)
• spi_queued_transfer(9)
• spi_flush_queue(9)
• of_register_spi_devices(9)
• spi_new_ancillary_device(9)
• devm_spi_new_ancillary_device(9)
• acpi_spi_count_resources(9)
• acpi_spi_device_alloc(9)
• spi_target_abort(9)
• __spi_alloc_controller(9)
• __devm_spi_alloc_controller(9)
• spi_get_gpio_descs(9)
• spi_register_controller(9)
• devm_spi_register_controller(9)
• spi_unregister_controller(9)
• spi_replace_transfers(9)
• spi_split_transfers_maxsize(9)
• spi_split_transfers_maxwords(9)
• spi_set_cs_timing(9)
• spi_setup(9)
• spi_optimize_message(9)
• spi_unoptimize_message(9)
• devm_spi_optimize_message(9)
• spi_async(9)
• spi_sync(9)
• spi_sync_locked(9)
• spi_bus_lock(9) ← the one that started it all 💜
• spi_write_then_read(9)

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and that's the whole page, bestie!! 🧚 mwah 💋

this little icon lives in ./drivers/spi, dated October 2026, and it's filed under spi_bus_unlock(9) — go forth and unlock responsibly, ily 🎀💖