GPIOLOCK(4)

🎀 GPIOLOCK(4) — the kernel interfaces manual page, bestie edition 🎀

okay so real talk, this is a page from the Kernel Interfaces Manual and it's about gpiolock, which is genuinely one of those "wait that's so cool" drivers once you get what it does. buckle up 🦋

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✨ NAME ✨

gpiolock — support for multi-position keylocks attached to GPIO pins 💅

like, actual physical keylocks. with keys. attached to pins. iconic.

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🌸 SYNOPSIS 🌸

gpiolock* at gpio? offset ? mask ?
gpiolock* at gpio?

both forms are valid, no cap — the long one if you're specifying where the pins live, the short one if you're not 💖

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💫 DESCRIPTION 💫

The gpiolock driver lets you connect multi-position keylocks over GPIO pins. yes, literally a keylock, like the ones on a server chassis, wired into your kernel 🗝️✨

so here's the vibe: the keylock driver registers with an in-kernel keylock supporting system, and it provides kauth(9) support through an experimental security model. note the word experimental — it's giving "we're trying something new, be cool about it" 🧪

you can query the keylock state using the hw.keylock sysctl variables. super convenient, lowkey the best part 🫶

important limits, don't skip these:

• Only locks with 2-4 positions are currently supported. that's the range. 2 to 4. periodt 💀
• The pin number is specified in the kernel configuration with the offset locator.
• The mask locator denotes the pins used for the lock — minimum 2, maximum 4 pins are used.

and here's the cute part: offset and mask can also be specified when gpiolock is attached at runtime, using the GPIOATTACH ioctl(2) on the gpio(4) device. runtime config, we love to see it 🌈

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🔥 SEE ALSO 🔥

• gpio(4)
• intro(4)

go read those too, they're the supporting cast and they ate 👑

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🌼 HISTORY 🌼

The gpiolock driver first appeared in NetBSD 6.0. a certified classic, honestly ⭐

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💜 AUTHORS 💜

The gpiolock driver was written by Marc Balmer <marc@msys.ch> — thank you king, we appreciate you 🙏

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bestie reminder: this is an experimental security model, and the lock only supports 2-4 positions with 2-4 mask pins. don't try to make it do more, it's not that kind of driver 🎀

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and that's the page! this edition of GPIOLOCK(4) comes from Debian, dated August 21, 2009 — mwah, bye bestie, go wire up a keylock 💋✨