cppc_set_auto_act_window(9)

💖 cppc_set_auto_act_window 💖

okay bestie, welcome to the Kernel API Manual, section 9 — yes we're in the kernel docs, yes it's giving big-brain energy, and yes you're gonna get it. this one's about writing to a register. a little register. a fancy little register. let's go 🎀

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✨ NAME ✨

cppc_set_auto_act_window — literally just writes the autonomous activity window register. that's the whole job. she's focused, she's employed, she slays 💅

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🌸 SYNOPSIS 🌸

int cppc_set_auto_act_window (int cpu , u64 auto_act_window );

returns an int, takes two args, no drama. 🦋

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🧚 ARGUMENTS 🧚

• cpu — the CPU you're writing the register on. like, which CPU, bestie. pick one. be specific 👑
• auto_act_window — the usec value you're writing into the autonomous activity window register. it's a u64, it's a usec value, it's the moment ✨

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🔥 DESCRIPTION 🔥

so according to ACPI 6.5, s8.4.6.1.6 (iykyk), the value you write to the autonomous activity window register isn't just one lil number — it's actually two parts glued together:

• a 7 bits value that indicates the significand
• a 3 bits value that indicates the exponent

that's it, that's the whole encoding. 7 + 3, a little math sandwich, no cap 🥪💀

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💜 SEE ALSO 💜

the whole friend group, fr fr — they all live in the kernel file ./drivers/acpi/cppc_acpi.c:

• acpi_get_psd_map(9)
• cpc_ffh_supported(9)
• cpc_supported_by_cpu(9)
• pcc_data_alloc(9)
• acpi_cppc_processor_probe(9)
• acpi_cppc_processor_exit(9)
• cpc_read_ffh(9)
• cpc_read_ffh_fb_ctrs(9)
• cpc_write_ffh(9)
• cppc_get_desired_perf(9)
• cppc_get_nominal_perf(9)
• cppc_get_highest_perf(9)
• cppc_get_epp_perf(9)
• cppc_get_perf_caps(9)
• cppc_perf_ctrs_in_pcc_cpu(9)
• cppc_perf_ctrs_in_pcc(9)
• cppc_get_perf_ctrs(9)
• cppc_set_epp(9)
• cppc_get_auto_act_window(9)
• cppc_get_auto_sel(9)
• cppc_set_auto_sel(9)
• cppc_set_enable(9)
• cppc_get_perf(9)
• cppc_set_perf(9)
• cppc_get_perf_limited(9)
• cppc_set_perf_limited(9)
• cppc_get_transition_latency(9)

go read them all, bestie, they're literally iconic 🌈⭐

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and that's the page!! 💖 shouting out ./drivers/acpi for keeping it real, and stamping it October 2026 like a lil time capsule 🎀🫶 you understood the assignment, bestie — now go write that register the correct way, periodt 🔥👑