__mmc_switch(9)

🎀 __mmc_switch(9) 🎀

okay so bestie, welcome to the Kernel API Manual — we're looking at __mmc_switch(9), and she's literally the function that modifies the EXT_CSD register. main character energy for MMC cards, no cap. 💅

💖 NAME 💖

__mmc_switch — modify EXT_CSD register. that's the whole vibe: one function, one register glow-up. ✨

✨ SYNOPSIS ✨

int __mmc_switch (struct mmc_card *card , u8 set , u8 index , u8 value ,
unsigned int timeout_ms , unsigned char timing , bool send_status , bool
retry_crc_err , unsigned int retries );

🎀 ARGUMENTS 🎀

• card — the MMC card associated with the data transfer. she's the main character here, obviously. 💳
• set — cmd set values. yep, exactly what it says.
• index — EXT_CSD register index. this is the lil address situation.
• value — value to program into the EXT_CSD register. the actual content going in.
• timeout_ms — timeout in milliseconds for the operation performed by the register write. a timeout of zero implies the maximum possible timeout — so bestie, zero does not mean "instant", it means "wait as long as possible". 😭
• timing — new timing to change to. glow-up timing, basically.
• send_status — send a status cmd to poll for busy. yes, we're checking if she's still working.
• retry_crc_err — retry when there are CRC errors when polling with CMD13 for busy. because sometimes the vibe check fails and we try again. 💀
• retries — number of retries. literally how many do-overs you get.

🦋 DESCRIPTION 🦋

Modifies the EXT_CSD register for the selected card. that's it, that's the function — pick a card, write the register, keep it cute. no extra lore needed. ✨

🌈 SEE ALSO 🌈

• Kernel file ./drivers/mmc/core/mmc_ops.c
• mmc_interrupt_hpi(9)
• mmc_run_bkops(9)
• mmc_read_tuning(9)

go read those if you want the full friend-group lore. iykyk. 🫶

xoxo, your kernel bestie 💋 — source/version: ./drivers/mmc/core, dated October 2026. periodt. 🎀