sdio_writesb(9)

💅 sdio_writesb — bestie's guide to yeeting bytes into a FIFO

okay so this is a page from the Kernel API Manual (section 9, the kernel-space girlies 💖), and it's all about sdio_writesb, which is lowkey iconic for one specific job: writing into the FIFO of an SDIO function. no cap, that's the whole vibe.

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✨ NAME ✨

sdio_writesb — write to a FIFO of a SDIO function 🎀

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🌸 SYNOPSIS 🌸

int sdio_writesb (struct sdio_func *func , unsigned int addr , void *src
, int count );

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🦋 ARGUMENTS 🦋

• func — the SDIO function you're accessing 💫 like, whose FIFO are we talking to
• addr — address of the (single byte) FIFO, yes literally one byte, that's the whole address, don't come for me
• src — the buffer holding the data you're about to write 👑 this is where your bytes live before they get sent
• count — number of bytes to write, so be honest about how many you're sending 🍓

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🌈 DESCRIPTION 🌈

So the way this works: sdio_writesb writes to the specified FIFO of a given SDIO function. That's it, that's the whole personality. ✨

The return value tells you whether the transfer succeeded or not — so like, check it, bestie, don't just ignore it and assume everything's fine 💀

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💜 SEE ALSO 💜

Kernel file ./drivers/mmc/core/sdio_io.c (the source of truth, go read it, iykyk 🧚), plus the whole friend group:

• sdio_claim_host(9)
• sdio_release_host(9)
• sdio_enable_func(9)
• sdio_disable_func(9)
• sdio_set_block_size(9)
• sdio_align_size(9)
• sdio_readb(9)
• sdio_writeb(9)
• sdio_writeb_readb(9)
• sdio_memcpy_fromio(9)
• sdio_memcpy_toio(9)
• sdio_readsb(9)
• sdio_readw(9)
• sdio_writew(9)
• sdio_readl(9)
• sdio_writel(9)
• sdio_f0_readb(9)
• sdio_f0_writeb(9)
• sdio_get_host_pm_caps(9)
• sdio_set_host_pm_flags(9)
• sdio_retune_crc_disable(9)
• sdio_retune_crc_enable(9)
• sdio_retune_hold_now(9)
• sdio_retune_release(9)

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💅 fr fr that's the whole page. go write to your FIFO, main character.

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big kiss, this came from ./drivers/mmc/core and it's dated October 2026 — slay, bye 🫶💖