apply_constraint(9)

💅 apply_constraint(9) — the Kernel API Manual moment

ok so bestie, we're in the Kernel API Manual, section 9, and today's main character is apply_constraint. no cap, this one's a little internal helper but she's important — she's the one actually pushing your power-management wishes into the system. 🎀

✨ NAME ✨

apply_constraint — Add/modify/remove device PM QoS request.

🦋 SYNOPSIS 🦋

int apply_constraint (struct dev_pm_qos_request *req , enum
pm_qos_req_action action , s32 value );

🌸 ARGUMENTS 🌸

• req — the constraint request to apply, like the little envelope you're handing over 💌
• action — the action to perform (add/update/remove). pick your fighter.
• value — the value to assign to the QoS request. this is the actual number, so be normal about it.

🔥 DESCRIPTION 🔥

okay so this is an internal function — like, not the one you call from your driver and post about, she's behind the scenes 👑 — and her whole job is updating the constraints list using the PM QoS core code, and then, if needed, calling the per-device callbacks.

that's it. the way that she just quietly does the plumbing so everything stays in sync. iconic behavior honestly 🫶

💜 SEE ALSO 💜

Kernel file ./drivers/base/power/qos.c — go read it, the lore is in there iykyk 📖

• __dev_pm_qos_flags(9)
• dev_pm_qos_flags(9)
• __dev_pm_qos_resume_latency(9)
• dev_pm_qos_read_value(9)
• dev_pm_qos_constraints_destroy(9)
• dev_pm_qos_add_request(9)
• __dev_pm_qos_update_request(9)
• dev_pm_qos_update_request(9)
• dev_pm_qos_remove_request(9)
• dev_pm_qos_add_notifier(9)
• dev_pm_qos_remove_notifier(9)
• dev_pm_qos_add_ancestor_request(9)
• dev_pm_qos_expose_latency_limit(9)
• dev_pm_qos_hide_latency_limit(9)
• dev_pm_qos_expose_flags(9)
• dev_pm_qos_hide_flags(9)
• dev_pm_qos_update_flags(9)
• dev_pm_qos_get_user_latency_tolerance(9)
• dev_pm_qos_update_user_latency_tolerance(9)
• dev_pm_qos_expose_latency_tolerance(9)
• dev_pm_qos_hide_latency_tolerance(9)

that's the whole page, bestie — go forth and constrain responsibly 🌈💖

source: ./drivers/base/power · version/date: October 2026 — mwah, signed off with love from your favorite kernel girlie 🧚✨