STRUCT SUBSYS_PRIVATE(9)

✨ struct subsys_private 💅 (from the Kernel API Manual, bestie)

okay so like… this page is literally about struct subsys_private, and yes it's exactly what it sounds like: it's the structure that holds all the private-to-the-driver-core bits of the bus_type/class structure. no cap, that's the whole vibe ✨

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🌸 NAME 🌸

struct subsys_private — the structure that holds the private, driver-core-only portions of the bus_type/class structure. it's giving "backstage pass, not for public consumption" 🎀

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🦋 SYNOPSIS 🦋

struct subsys_private {
    struct kset subsys;
    struct kset *devices_kset;
    struct list_head interfaces;
    struct mutex mutex;
    struct kset *drivers_kset;
    struct klist klist_devices;
    struct klist klist_drivers;
    struct blocking_notifier_head bus_notifier;
    unsigned int drivers_autoprobe:1;
    const struct bus_type *bus;
    struct device *dev_root;
    struct kset glue_dirs;
    const struct class *class;
    struct lock_class_key lock_key;
 };

like, look at her. iconic. absolutely ate that struct definition 👑

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🧚 Members (the whole cast, no skips) 🧚

• subsys — the struct kset that defines this subsystem. it's the main character of the whole operation tbh.
• devices_kset — the subsystem's 'devices' directory. like, where the devices live 🏠
• interfaces — the list of subsystem interfaces associated. lowkey just a list of who's hanging out here.
• mutex — protects the devices and interfaces lists. do not skip the lock, bestie, fr fr 😭
• drivers_kset — the list of drivers associated. the driver squad 🚗
• klist_devices — the klist you use to iterate over the devices_kset. that's the whole job. iykyk.
• klist_drivers — the klist to iterate over the drivers_kset. same energy, different list 💫
• bus_notifier — the bus notifier list, for anything that cares about things on this bus. and yes, some things really do care 👀
• drivers_autoprobe — the gate that decides whether new devices automatically get attached to registered drivers, or new drivers automatically attach to existing devices. it's literally a unsigned int drivers_autoprobe:1 bitfield. one single bit running the whole show 💀
• bus — pointer back to the struct bus_type that this structure is associated with. a little "take me home" pointer 🫶
• dev_root — the default device to use as the parent. every icon needs a parent, periodt.
• glue_dirs — the "glue" directory that goes in-between the parent device so you avoid namespace conflicts. it's the buffer friend at the party 🎀
• class — pointer back to the struct class that this structure is associated with. matching set with bus, obviously ✨
• lock_key — the lock class key, for use by the lock validator. very responsible of her ngl 🔐

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💖 Description 💖

so here's the tea: this structure is the one — it's the actual kobject that lets struct bus_type/class be statically allocated safely. that's the flex. 🏆

⚠️ real talk: nothing outside of the driver core should ever touch these fields. not you, not your friend, not your friend's friend. hands off, bestie 🙈

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🌈 SEE ALSO 🌈

• Kernel file ./drivers/base/base.h
• struct device_private(9) — go read that one next, it's connected, trust 🦋

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and that's the page! 🫶 shoutout to ./drivers/base for hosting this one, this is the Kernel API Manual, dated October 2026, and this has been your girl explaining struct subsys_private(9) — stay safe, lock your mutexes, and don't touch driver-core fields 💅✨👑