spi_sync_locked(9)

💅 spi_sync_locked(9) — the kernel API manual, bestie edition

okay so this is a page from the Kernel API Manual (yes, the (9) one, kernel-doc section, we're fancy here) and it's all about spi_sync_locked — the version of spi_sync that gets the SPI bus all to itself 🔒✨

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🌸 NAME 🌸

spi_sync_locked — literally the version of spi_sync with exclusive bus usage, no cap 👑

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🎀 SYNOPSIS 🎀

int spi_sync_locked (struct spi_device *spi , struct spi_message
*message );

that's the whole signature, she's not complicated 💅

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🦋 ARGUMENTS 🦋

• spi — the device with which data will be exchanged 🫶
• message — describes the data transfers 📨

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💜 CONTEXT 💜

cannot sleep? no bestie, the opposite — can sleep 😴✨

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🔥 DESCRIPTION 🔥

So here's the tea ☕ — this call may only be used from a context that may sleep. And the sleep? It's non-interruptible, and it has no timeout. So like… she's committed. She's not waking up early, she's not checking her phone, she's just in it until it's done 😭

Also, low-overhead controller drivers may DMA directly into and out of the message buffers. iconic behaviour honestly 🎀

This call should be used by drivers that require exclusive access to the SPI bus. It has to be preceded by a spi_bus_lock call — like, you literally can't skip that step, it's giving prerequisites, it's giving prerequisites-fr-fr. And when the exclusive access is over, the SPI bus must be released by a spi_bus_unlock call. lock → do the thing → unlock. the trinity 🤝

lowkey a vibe check on your locking discipline: forget the unlock and everyone's stuck. just saying 🙈

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⭐ RETURN ⭐

zero on success 🎉 — else a negative error code 💀

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🌈 SEE ALSO 🌈

okay this list is long but we do not skip, we do not summarise, we list every single one because that's the assignment 💅 The Kernel file is ./drivers/spi/spi.c and here's everybody:

• __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_bus_lock(9)
• spi_bus_unlock(9)
• spi_write_then_read(9)

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and that's the page, bestie 🫶 this one lives under ./drivers/spi, dated October 2026, and it's spi_sync_locked(9) all the way down — go lock that bus, slay responsibly, and remember to unlock 💖✨🎀