> For the complete documentation index, see [llms.txt](https://book.bsdcn.org/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://book.bsdcn.org/man/man4/acpi_video.4.md).

# acpi\_video.4

`acpi_video` — ACPI 视频扩展驱动

## 名称

`acpi_video`

## 概要

`device acpi_video`

## 描述

此驱动使用 ACPI 视频扩展来控制显示切换和背光亮度。[sysctl(8)](/man/man8/sysctl.8.md) 变量的可用性取决于主机的 ACPI 实现所提供的功能。

## SYSCTL 变量

目前实现了以下 sysctl，其中 <`device`> 为 `crt`、`lcd` 或 `tv`：

**`hw.acpi.video.`** <`device`>`.active` 输出设备的当前状态。

**`hw.acpi.video.`** <`device`>`.levels` 支持的亮度级别列表。

**`hw.acpi.video.`** <`device`>`.brightness` 设备当前的亮度级别。

**`hw.acpi.video.`** <`device`>`.fullpower` 全功率模式下使用的预设亮度级别。

**`hw.acpi.video.`** <`device`>`.economy` 经济模式下使用的预设亮度级别。

这些变量的默认值可在 [sysctl.conf(5)](/man/man5/sysctl.conf.5.md) 中设置，该文件在引导时解析。

## 兼容性

为使 `acpi_video` 正确附加，`acpi_video` 应在任何 DRM 内核模块之后加载。这可通过在 [rc.conf(5)](/man/man5/rc.conf.5.md) 中使用 kld\_list 指令设置正确的顺序来实现。

## 参见

[acpi(4)](/man/man4/acpi.4.md), loader.conf(5), [sysctl.conf(5)](/man/man5/sysctl.conf.5.md), [sysctl(8)](/man/man8/sysctl.8.md)

## 历史

`acpi_video` 驱动首次出现于 FreeBSD 5.3。

## 作者

`acpi_video` 驱动由 Taku YAMAMOTO <taku@cent.saitama-u.ac.jp> 编写。本手册页由 Mark Santcroos <marks@ripe.net> 编写。

## 缺陷

某些系统尽管通过 ACPI 导出了正确的信息，但仅通过 SMM 执行输出切换。在此类系统上，必须改用相应的热键或 OEM 驱动（例如 [acpi\_toshiba(4)](/man/man4/acpi_toshiba.4.md)）。


---

# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.

## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter:

```
GET https://book.bsdcn.org/man/man4/acpi_video.4.md?ask=<question>&goal=<endgoal>
```

`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal.

The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.