cdns_transfer_one(9)

💅 cdns_transfer_one — like, the whole page, bestie

okay so this is a page from the Kernel API Manual (yes, the fancy one, section 9, kernel-space royalty 👑) and it's all about one little function that gets the SPI party started. Let's get into it ✨

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🌸 NAME 🌸

cdns_transfer_one — literally just starts the SPI transfer. That's the whole vibe check. One job, and it ate. 💅

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🦋 SYNOPSIS 🦋

int cdns_transfer_one (struct spi_controller *ctlr , struct spi_device
*spi , struct spi_transfer *transfer );

copy it exactly please, no cap — the spacing and the stray line-break are part of the ~aesthetic~ (it's giving old manpage energy 🙈).

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🎀 ARGUMENTS 🎀

• ctlr — a pointer to the spi_controller structure 🎮 like, the controller in question.
• spi — a pointer to the spi_device structure 📱 the device we're talking to.
• transfer — a pointer to the spi_transfer structure, which is the one that spills all the tea ☕ about what the next transfer's parameters are.

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✨ DESCRIPTION ✨

bestie, this function has two whole personalities depending on the mode, and both of them slay:

• In host mode — it fills up the TX FIFO, kicks off the SPI transfer, and then returns a positive transfer count so the core knows to sit there and wait for completion 🫶 (like "yes queen, it's coming, hold on").
• In target mode — it fills the TX FIFO and then just… waits for the transfer trigger 🌸 patient icon behaviour, honestly.

ngl, the two modes do not do the same thing, so don't get it twisted — host mode starts the thing and hands back a count; target mode fills the FIFO and waits for the trigger. 💀

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🔥 RETURN 🔥

Returns the number of bytes transferred in the last transfer ✨ that's the number, that's the answer, periodt.

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💜 SEE ALSO 💜

omg okay so the whole friend group, all in one place 🫶 — every one of these is in Kernel file ./drivers/spi/spi-cadence.c:

• struct cdns_spi(9)
• cdns_spi_init_hw(9)
• cdns_spi_chipselect(9)
• cdns_spi_config_clock_mode(9)
• cdns_spi_config_clock_freq(9)
• cdns_spi_setup_transfer(9)
• cdns_spi_process_fifo(9)
• cdns_spi_irq(9)
• cdns_prepare_transfer_hardware(9)
• cdns_unprepare_transfer_hardware(9)
• cdns_spi_detect_fifo_depth(9)
• cdns_target_abort(9)
• cdns_spi_probe(9)
• cdns_spi_remove(9)
• cdns_spi_suspend(9)
• cdns_spi_resume(9)
• cdns_spi_runtime_resume(9)
• cdns_spi_runtime_suspend(9)

like, the entire cadence SPI cinematic universe 🌈 iykyk.

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✨ that's the whole page, bestie, every last crumb ✨

and for the cute sign-off 🎀: this lil masterpiece lives over in ./drivers/spi and it's dated October 2026 — so future-coded of it honestly. go forth and transfer responsibly 💖🦋