对于本项目，我们需要有 ddcutil 库才能通过 I2C 访问 HDMI 显示设置。要将 ddcutil 库包含到您的定制 linux 系统中，您必须为其创建定制方案。#### ddcutil_git.bb 方案

在您的定制 meta 层中创建文件夹“recipes-support/ddcutil”。在此文件夹中，创建文件“ddcutil_git.bb”。

SUMMARY = "Tool to modify display settings by ddc (hdmi)"
HOMEPAGE = "http://www.ddcutil.com"
AUTHOR = "Sanford Rockowitz  rockowitz@minsoft.com"
LICENSE = "GPLv2"
LIC_FILES_CHKSUM = "file://COPYING;md5=b234ee4d69f5fce4486a80fdaf4a4263"
BRANCH = "master"
SRCREV = "5080161b456cc6a1fd3e6db3dc537e1dcd1c809b"
PV = "1.2.2+${SRCPV}"
SRC_URI = " 

git://github.com/rockowitz/ddcutil;branch=${BRANCH};protocol=https; 

"
disable trying to fetch from mirrors
PREMIRRORS = ""
MIRRORS = ""
DEPENDS += "

i2c-tools 

libusb1 

libdrm 

libgudev 

"
RDEPENDS_${PN} += "

i2c-tools 

i2c-tools-misc 

libdrm 

"
S = "${WORKDIR}/git"
EXTRA_OECONF += "

--disable-x11 --enable-drm --disable-usb --enable-lib --disable-doxygen 

"
inherit autotools pkgconfig

将 ddcutil 包含到您的镜像种

您必须将方案包含在您的 Yocto Linux 中：

IMAGE_INSTALL:append = " ddcutil"

您现在可以对您的对镜像执行 bitbake 命令并测试结果。

登录到您的定制嵌入式系统或通过 SSH 连接。现在，您可以使用 ddcutil 命令查看该实现是否成功。#### 探测到报告显示器

首先，您可以检测 HDMI 监视器是否已连接并可通过 ddcutil 使用。使用以下命令：

ddcutil detect

输出应该是这个样子：

Display 1
   I2C bus:  /dev/i2c-3
   EDID synopsis:
      Mfg id:               IVM
      Model:                PLT2236
      Product code:         22057
      Serial number:        11402A7100051
      Binary serial number: 51 (0x00000033)
      Manufacture year:     2017,  Week: 1
   VCP version:         2.1

获取所有设置

要获取所有设置，请使用以下命令：

ddcutil getvcp all

输出应该是这个样子：

VCP code 0x02 (New control value             ): No user controls are present (0xff)
VCP code 0x0b (Color temperature increment   ): 50 degree(s) Kelvin
VCP code 0x0c (Color temperature request     ): 3000 + 70 * (feature 0B color temp increment) degree(s) Kelvin
VCP code 0x10 (Brightness                    ): current value =   100, max value =   100
VCP code 0x12 (Contrast                      ): current value =    50, max value =   100
VCP code 0x14 (Select color preset           ): User 1 (sl=0x0b)
VCP code 0x16 (Video gain: Red               ): current value =   100, max value =   100
VCP code 0x18 (Video gain: Green             ): current value =   100, max value =   100
VCP code 0x1a (Video gain: Blue              ): current value =   100, max value =   100
VCP code 0x52 (Active control                ): Value: 0x00
VCP code 0x60 (Input Source                  ): DVI-1 (sl=0x03)
VCP code 0x62 (Audio speaker volume          ): current value =    49, max value =   100
VCP code 0x6c (Video black level: Red        ): current value =    50, max value =   100
VCP code 0x6e (Video black level: Green      ): current value =    50, max value =   100
VCP code 0x70 (Video black level: Blue       ): current value =    50, max value =   100
VCP code 0x8d (Audio Mute                    ): Unmute the audio (sl=0x02)
VCP code 0xac (Horizontal frequency          ): 1964 hz
VCP code 0xae (Vertical frequency            ): 60.00 hz
VCP code 0xb2 (Flat panel sub-pixel layout   ): Red/Green/Blue vertical stripe (sl=0x01)
VCP code 0xb6 (Display technology type       ): LCD (active matrix) (sl=0x03)
VCP code 0xc0 (Display usage time            ): Usage time (hours) = 1030 (0x000406) mh=0xff, ml=0xff, sh=0x04, sl=0x06
VCP code 0xc6 (Application enable key        ): 0x006f
VCP code 0xc8 (Display controller type       ): Mfg: Novatek (sl=0x12), controller number: mh=0xff, ml=0xff, sh=0x00
VCP code 0xc9 (Display firmware level        ): 0.2
VCP code 0xca (OSD                           ): OSD Enabled (sl=0x02)
VCP code 0xcc (OSD Language                  ): English (sl=0x02)
VCP code 0xd6 (Power mode                    ): DPM: On,  DPMS: Off (sl=0x01)
VCP code 0xdc (Display Mode                  ): User defined (sl=0x04)
VCP code 0xdf (VCP Version                   ): 2.1

设置亮度

要将显示器的亮度设置为 50 %，请使用以下命令：

ddcutil setvcp 10 50

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本项目源代码根据 GPL-3.0 许可证获得许可。