spi_sync(9)

💅 spi_sync(9) — the manual page, bestie edition

okay so this is a Kernel API Manual page for spi_sync, and honestly? it's a whole vibe. it's the "just do it synchronously and let me nap until it's done" SPI transfer call 🦋

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✨ NAME ✨

spi_sync — blocking/synchronous SPI data transfers 🌸

like, you hand it a message, you wait, you get your answer. no callbacks, no chaos, no "we'll get back to you." periodt.

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✨ SYNOPSIS ✨

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

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✨ ARGUMENTS ✨

• spi — the device you're exchanging data with 🫶 like, who are we talking to
• message — describes the data transfers — the whole itinerary of the trip, basically

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✨ CONTEXT ✨

can sleep 😴

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✨ DESCRIPTION ✨

okay so the big rule: this call may only be used from a context that may sleep. and not like a cute little nap either — the sleep is non-interruptible, and it has no timeout. it's giving main character energy that refuses to be woken up early 💀

the good news? low-overhead controller drivers may DMA directly into and out of the message buffers. highkey efficient. 🔥

also note 👀 — the SPI device's chip select is active during the message, and then is normally disabled between messages. some drivers for frequently-used devices might wanna minimize the cost of selecting a chip by leaving it selected, anticipating that the next message goes to the same chip. (just know that may increase power usage 🌈)

and one more thing, bestie, this is important: the caller is guaranteeing that the memory associated with the message will not be freed before this call returns. no cap. if you free it early, that's on you 🙈

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✨ RETURN ✨

zero on success ✨ else a negative error code 😭

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✨ SEE ALSO ✨

kernel file ./drivers/spi/spi.c and the whole friend group:

• __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_locked(9)
• spi_bus_lock(9)
• spi_bus_unlock(9)
• spi_write_then_read(9)

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ok that's the whole page, no details skipped, i promise 🎀 go forth and transfer synchronously, queen 👑

and that's a wrap! this one came from the ./drivers/spi directory, dated October 2026 — mwah, tysm for reading, ily, bye 💖✨🧚