ACPIVGA(4)

✨ ACPIVGA(4) — like, the ACPI Display Adapter & Output Devices page, but make it make sense ✨

okay bestie, so this one lives in the Kernel Interfaces Manual section, and it's genuinely one of those pages that sounds scary but is actually just "your laptop screen brightness + which screen stuff goes to" energy. let's get into it 💅

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🌸 SYNOPSIS 🌸

acpivga* at acpi?
acpiout* at acpivga?

that's it. that's the whole configuration vibe. acpivga* attaches at acpi?, and acpiout* attaches at acpivga? — the outputs are literally the children of the adapter, iykyk 🦋

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💖 DESCRIPTION 💖

so the acpivga driver is the generic-support bestie for brightness control and output switching, and it does all of that through the ACPI video extensions. and here's the thing — the ACPI specification requires that systems with a built-in display adapter implement these extensions in their ACPI BIOS. so if your machine has a screen built in, the BIOS is supposed to have this. periodt ✨

the driver handles brightness hotkeys and display switch hotkeys — like when you smash the fn key with the sun icon, that's her 💅

on top of that, you get these sysctl(8) read/write variables, but only when hardware support is actually available (vibe check first, always):

• hw.acpi.acpivga0.bios_switch — the BIOS output switching policy. this is a boolean, and it controls how the BIOS behaves when a display switch hotkey gets pressed 🎀
  • 1 — the BIOS should automatically switch outputs, with no interaction from acpivga. she handles it, you don't even have to ask.
  • 0 — the BIOS should only notify acpivga of the desired output state changes. so it tells her, and she does the actual work.
• hw.acpi.acpiout0.brightness — the brightness level, obviously 💡 this integer variable typically ranges from 0 to 100, but honestly any integer value is accepted — the driver just uses the closest brightness level the device actually supports. so go off, put 9999, she'll cope.

⚠️ ok important heads up bestie: future versions of acpivga may remove these sysctl(8) variables without prior notice. no warning, no text, no nothing 😭 so don't build your whole personality on them.

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🦋 SEE ALSO 🦋

• acpi(4)
• vga(4)
• sysctl(8)

also this reference, which is very "cited source realness":

Microsoft Corporation, Mobile System Displays and Windows, Version 1.2c, http://www.microsoft.com/whdc/archive/mobiledisplay.mspx, December 4, 2001.

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👑 HISTORY 👑

the acpivga driver appeared in NetBSD 6.0. a legend was born ✨

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🫶 AUTHORS 🫶

Grégoire Sutre ⟨gsutre@NetBSD.org⟩ — thank you for your service, icon 🌈

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💀 CAVEATS 💀

okay this is the part where we get real, no cap:

• the acpivga driver only supports PCI/PCI-X/PCI-E display adapters. that's the whole list. if yours isn't one of those, she can't help you 🙈
• many ACPI BIOSes implement only part of the ACPI video extensions. and in particular, display output switching via these extensions often does not work. yes, really. it's giving "we tried" 😭
• for that exact reason, acpivga enables hw.acpi.acpivga0.bios_switch by default. so if the display switch hotkey doesn't work with that default setting, try setting hw.acpi.acpivga0.bios_switch to 0. that's your troubleshooting move, bestie 🎀
• brightness level should be controlled via wsconsctl(8) instead of sysctl(8) — like, that's the correct door to walk through, ok? don't do it the other way 💅

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anyway that's the page!! written by the Debian crew and dated October 28, 2010 — a whole vintage moment ⭐ slay, bye 💜