bus_for_each_dev(9)

💅 bus_for_each_dev(9) — like, the device iterator bestie

okay so this is a page straight out of the Kernel API Manual (bus_for_each_dev(9), yes that's the whole vibe) and it's literally about walking a bus's device list and doing stuff to every single one. no cap, it's a for-each loop but make it kernel ✨

---

🌸 SYNOPSIS 🌸

int bus_for_each_dev (const struct bus_type *bus , struct device *start
, void *data , device_iter_t fn );

that's the whole signature, character for character, don't come for me 🫶

---

🎀 ARGUMENTS 🎀

• bus — the bus type. like, which bus we're strolling through 💖
• start — the device you wanna start iterating from. your starting point, your main character device 👑
• data — the data handed off to the callback. lil care package for fn 🎁 (well, the page calls it data, and data it is)
• fn — the function that gets called for each device. one call per device, no skips 🦋

---

✨ DESCRIPTION ✨

so here's the tea: this thing iterates over bus's list of devices, and it calls fn for each one, passing it data. that's it, that's the loop 💅

and if start is not NULL? we use that device to begin iterating from — like picking up the convo mid-scroll 🙈

every single time, we check the return of fn. and if it returns anything other than 0, we break out and return that value. periodt. non-zero means we're done, bestie, we're leaving 🏃‍♀️💨

---

💀 NOTE 💀

listen, this part is important and also a lil scary: the device that returns a non-zero value is not retained in any way, and its refcount is not incremented. like, at all. zero. nada 😭

so if the caller needs to retain this data, it should do so — and increment the reference count in the supplied callback. that's on you, not on us 🫶 don't forget, fr fr.

---

🔥 SEE ALSO 🔥

kernel file ./drivers/base/bus.c plus the whole friend group:

bus_to_subsys(9), bus_find_device(9), bus_for_each_drv(9), bus_add_device(9), bus_probe_device(9), bus_remove_device(9), bus_add_driver(9), bus_remove_driver(9), bus_rescan_devices(9), device_reprobe(9), bus_register(9), bus_unregister(9), subsys_dev_iter_init(9), subsys_dev_iter_next(9), subsys_dev_iter_exit(9), subsys_system_register(9), subsys_virtual_register(9), driver_find(9), bus_get_dev_root(9)

all iconic, all worth a read, iykyk 🌈⭐

---

and that's the page!! brought to you by the fine folks over at ./drivers/base, dated October 2026, page bus_for_each_dev(9) — mwah, go iterate something 💜🧚‍♀️