class_find_device(9)

📦 version 7.3.1, in nixpkgs unstable

💅 class_find_device — bestie's guide to finding one specific device

ok so real talk, you're in the Kernel API Manual (section 9, kernel internals, iykyk) and the function we're stanning today is class_find_device, and honestly? it's giving "where's that one device" energy. it's the device iterator that goes looking for a particular device instead of just vibing through the whole class. let's get into it 🎀

✨ SYNOPSIS ✨

struct device * class_find_device (const struct class *class , const
       struct device *start , const void *data , device_match_t match );

like, four args, one struct device * back. clean. iconic. no notes. 🌸

🫶 ARGUMENTS 🫶

  • class — the class we're iterating, aka the friend group we're scrolling through 👑
  • start — Device to begin with, aka where you start scrolling from (yes, literally the starting device)
  • data — data for the match function — this is the little care package you hand to your callback so it knows what it's looking for 🎁
  • match — function to check device — the vibe check callback, the one who decides who's the one 🔥

💖 DESCRIPTION 💖

so this is similar to the class_for_each_dev function above, but instead of just doing a drive-by over everything, it returns a reference to a device that is 'found' for later use, as determined by the match callback. so you're not just visiting — you're keeping one. main character device energy fr fr 💅

the callback should return 0 if the device doesn't match and non-zero if it does. if the callback returns non-zero, this function will return to the caller and not iterate over any more devices — it's done, it found its person, the search is over, periodt 🦋

⚠️ okay bestie listen — you will need to drop the reference with put_device after use. do not forget. do not leave it hanging. that's a refcount leak and we do NOT do that in this house 😭

and here's the cute part: match is allowed to do anything including calling back into class code. there's no locking restriction. no cap. go wild. 🌈

🔍 SEE ALSO 🔍

Kernel file ./drivers/base/class.c — and the whole squad:

and that's the whole page, bestie 💜 this lil slice of kernel knowledge lives in ./drivers/base, stamped October 2026, under the class_find_device(9) banner — go forth, find your device, and remember to put_device 🫶✨

📦 where this page comes from