spi_w8r16(9)

💫 spi_w8r16(9) 💫

ok so welcome to the Kernel API Manual bestie, this is the page for spi_w8r16 and honestly? it's a little cutie. tiny function, big job. let's get into it 🎀

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✨ NAME ✨

spi_w8r16 — SPI synchronous 8 bit write followed by 16 bit read 🦋

like, you write 8 bits out, then read 16 bits back. sales. slay. periodt.

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🌸 SYNOPSIS 🌸

ssize_t spi_w8r16 (struct spi_device *spi , u8 cmd );

that's the whole thing. one spi, one cmd, one ssize_t coming back atcha 💅

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🧚 ARGUMENTS 🧚

• spi — the device you're exchanging data with. that's your main character, the one you're talking to over SPI 💖
• cmd — the command that gets written before the data is read back. so it goes out first, then we pull the answer in. iykyk 🔥

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⭐ CONTEXT ⭐

can sleep 😴

no cap, this one's allowed to nap. it's not one of those feral atomic-context functions.

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💜 DESCRIPTION 💜

ok so the number comes back in wire-order, which is at least sometimes big-endian. the manual is literally saying "at least sometimes" and honestly? relatable. byte order is a whole vibe and it is NOT always consistent 🙈

also, real talk: this is callable only from contexts that can sleep. 🫶 so no, you can't just drop it in an interrupt handler and hope for the best. it needs a context that's allowed to block. lowkey important.

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🌈 RETURN 🌈

you get back the (unsigned) sixteen bit number that the device returned 💖

or, if things went sideways, a negative error code 😭 (yes, negative. check it. always check it. ngl the error code is the drama and you don't want it.)

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👑 SEE ALSO 👑

like a whole friend group honestly, look at this squad:

• Kernel file ./include/linux/spi/spi.h
• struct spi_statistics(9)
• struct spi_delay(9)
• struct spi_device(9)
• struct spi_driver(9)
• spi_unregister_driver(9)
• module_spi_driver(9)
• struct spi_controller(9)
• struct spi_res(9)
• struct spi_transfer(9)
• struct spi_message(9)
• spi_message_init_with_transfers(9)
• spi_is_bpw_supported(9)
• spi_bpw_to_bytes(9)
• spi_controller_xfer_timeout(9)
• struct spi_replaced_transfers(9)
• spi_sync_transfer(9)
• spi_write(9)
• spi_read(9)
• spi_w8r8(9)
• spi_w8r16be(9)
• struct spi_board_info(9)

the way that list just keeps going… obsessed 💀 but fr fr, if you're messing with SPI you're gonna want these.

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and that's the page!! 🫶 bye bestie, go forth and read your 16 bits 💖✨🎀

from ./include/linux/spi, dated October 2026 — mwah, see u in the next manpage 💅🍓