sdio_readb(9)

💅 sdio_readb(9) 💅

okay so this is sdio_readb(9) from the Kernel API Manual, and it's giving “read one single byte from a SDIO function” energy. no cap, that's the whole vibe. 🦋

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🌸 NAME 🌸

sdio_readb — read a single byte from a SDIO function

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🎀 SYNOPSIS 🎀

so the signature is literally right here, bestie:

u8 sdio_readb (struct sdio_func *func , unsigned int addr , int *err_ret
);

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✨ ARGUMENTS ✨

• func — the SDIO function to access. that's the main character you're working with 💖
• addr — the address to read. yes, the actual address, don't skip it 🎯
• err_ret — optional status value from the transfer. it's optional, but it's there if you need the status tea ☕

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💖 DESCRIPTION 💖

Reads a single byte from the address space of a given SDIO function. simple, iconic, one byte at a time. 💅

If there's a problem reading the address, 0xff is returned, and err_ret will contain the error code. so yeah, if things go sideways, 0xff is the little “something went wrong” signal, and err_ret has the actual error code. periodt. 🔥

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🔥 SEE ALSO 🔥

Kernel file: ./drivers/mmc/core/sdio_io.c — go check it out, iykyk 👑

and these besties are all in the SEE ALSO circle too:

• 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_writeb(9)
• sdio_writeb_readb(9)
• sdio_memcpy_fromio(9)
• sdio_memcpy_toio(9)
• sdio_readsb(9)
• sdio_writesb(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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that's the whole page, bestie 🫶 sending you off with the source/version ./drivers/mmc/core and the date October 2026 for sdio_readb(9) — mwah 💋✨