mmc_regulator_get_supply(9)

💖 mmc_regulator_get_supply(9) — the Kernel API Manual glow-up 💖

okay so bestie, we're in the Kernel API Manual today and the star of the show is mmc_regulator_get_supply — yes the (9) is the section, yes it's giving kernel-internals, and yes we're gonna get through it together 🫶

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✨ NAME ✨

mmc_regulator_get_supply — the function that tries to get VMMC</> and VQMMC</> regulators for a host. that's it, that's the whole vibe. it's literally in the name, no cap 💅

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🌸 SYNOPSIS 🌸

int mmc_regulator_get_supply (struct mmc_host *mmc );

look at her. one function, one argument, zero drama (well, ok, a little drama — see DESCRIPTION) 🎀

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🦋 ARGUMENTS 🦋

• mmc — the host to regulate. that's the struct mmc_host * bestie, the main character of this whole operation 👑

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💀 DESCRIPTION 💀

so what does she actually return? she returns 0 or an errno. simple, right? no. because you have to handle that errno — it's either a critical error or -EPROBE_DEFER, and those are two very different situations, so don't just ignore it and hope for the best 😭

and here's the part that gets people every single time: 0 means no critical error, but it does NOT mean all the regulators have been found. not even close, bestie. because they're all optional. every last one. so a happy little 0 is like a "we didn't crash" not a "everything is perfect" 💀

so if your driver actually requires certain regulators? you have to check separately in your driver whether they got populated after calling this function. like, do your own vibe check, don't make her do it for you 🙈

fr fr, re-read that bit. 0 ≠ "all regulators found". it's a trap and it's lowkey iconic for how many people it catches 🪤

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🌈 SEE ALSO 🌈

• Kernel file ./drivers/mmc/core/regulator.c
• mmc_ocrbitnum_to_vdd(9)
• mmc_regulator_get_ocrmask(9)
• mmc_regulator_set_ocr(9)
• mmc_regulator_set_vqmmc(9)
• mmc_regulator_set_vqmmc2(9)
• mmc_regulator_register_undervoltage_notifier(9)
• mmc_regulator_unregister_undervoltage_notifier(9)
• mmc_regulator_enable_vqmmc(9)
• mmc_regulator_disable_vqmmc(9)

the whole regulator friend group ate, ngl — go read them all 🍓

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and that's the page!! 💜 this cutie lives in ./drivers/mmc/core and the version notice is dated October 2026, so like… future girl summer 🌸 stay regulated, bestie, and remember: 0 is not a promise, it's a starting point ✨🎀🦋