usb_acpi_add_usb4_devlink(9)

💅 usb_acpi_add_usb4_devlink (9) — from the Kernel API Manual, bestie ✨

okay so picture this: it's a kernel manpage, it's about USB4 tunneling, and it's lowkey iconic. this is usb_acpi_add_usb4_devlink, and no cap, she's a whole vibe. let's get into it 🫶

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🌸 NAME 🌸

usb_acpi_add_usb4_devlink — adds a device link to the USB4 Host Interface for tunneled USB3 devices 🦋

like yes, that's the whole bit. she links things. respectfully. 💅

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✨ SYNOPSIS ✨

int usb_acpi_add_usb4_devlink (struct usb_device *udev );

one function, one arg, one return type. minimal, clean, ate. 👑

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🎀 ARGUMENTS 🎀

• udev — the tunneled USB3 device that's connected to a roothub. that's her. that's the queen in question. 🌈

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💖 DESCRIPTION 💖

so what she actually does: she adds a device link between a tunneled USB3 device and the USB4 Host Interface device. why? to ensure correct runtime PM suspend and resume order. it's giving "choreography" honestly — everybody has to wake up and go to sleep in the right sequence or the whole thing falls apart. 😭

big important note, bestie: this function should only be called for tunneled USB3 devices. read that again. don't be out here calling it on random devices, that's not the vibe. 🚫

and where does she find the USB4 Host Interface that this tunneled device depends on? she gets it from the roothub port's ACPI device specific data _DSD entry. iykyk. 🧚

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💀 RETURN 💀

• negative error code on failure 😔
• 0 otherwise ✅

that's it. no in-between. slay. 🍓

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🌟 SEE ALSO 🌟

• kernel file ./drivers/usb/core/usb-acpi.c — literally the source, go read her 📖
• usb_acpi_power_manageable(9)
• usb_acpi_port_lpm_incapable(9)
• usb_acpi_set_power_state(9)

the whole friend group fr fr 🫶

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and that's the page!! 💜 this little baddie lives over in ./drivers/usb/core, and this edition is dated October 2026 — go off, calendar icon. 🎀✨ see you in the group chat, bestie 💖