VESA DDC连接是一个I2C连接，可用于查询监视器的存在。
Linux暴露了I2C设备，用户程序可以直接与监视器通信，代码如http://jaffar.cs.msu.su/oleg/ddcci/
请注意以下内容：Control 0xe1: +/1/1 [SAM: Power control (0 - off/1 - on)]
# ddcci-tool /dev/i2c-2 -e -c -d
ddcci-tool version 0.03
Reading EDID : 0x50@/dev/i2c-2
Plug and Play ID: SAM00BA
Input type: Analog
Using ddc/ci : 0x37@/dev/i2c-2
Capabilities:
(type(LCD)vcp(04 05 10 12 60(1 3) B0(1 2) B6 C6 C8 C9 D6(1 4) DC(1 2 3 4) DF))
Controls (valid/current/max):
Control 0x04: +/0/1 [Reset Factory Defaults]
Control 0x05: +/0/1 [SAM: Reset Brightness and Contrast]
Control 0x06: +/0/1 [Reset Factory Geometry]
Control 0x08: +/0/1 [Reset Factory Default Color]
Control 0x0e: +/60/120 [SAM: Image Lock Coarse]
Control 0x10: +/0/100 [Brightness]
Control 0x12: +/50/100 [Contrast]
Control 0x16: +/8/16 [Red Video Gain]
Control 0x18: +/8/16 [Green Video Gain]
Control 0x1a: +/8/16 [Blue Video Gain]
Control 0x1e: +/0/2 [SAM: Auto Size Center]
Control 0x20: +/50/100 [Horizontal Position]
Control 0x30: +/25/54 [Vertical Position]
Control 0x3e: +/39/50 [SAM: Image Lock Fine]
Control 0x60: +/1/3 [Input Source Select]
Control 0x62: +/0/100 [Audio Speaker Volume Adjust]
Control 0x6c: +/140/255 [Red Video Black Level]
Control 0x6e: +/127/255 [Green Video Black Level]
Control 0x70: +/121/255 [Blue Video Black Level]
Control 0xb0: +/0/2 [Settings]
Control 0xb6: +/3/8 [???]
Control 0xc6: +/1/1 [???]
Control 0xc8: +/5/16 [???]
Control 0xc9: +/1/0 [???]
Control 0xca: +/2/2 [On Screen Display]
Control 0xcc: +/2/11 [SAM: On Screen Display Language]
Control 0xd6: +/1/4 [SAM: DPMS control (1 - on/4 - stby)]
Control 0xdc: +/4/4 [SAM: MagicBright (1 - text/2 - internet/3 - entertain/4 - custom)]
Control 0xdf: +/512/0 [VCP Version]
Control 0xe0: +/0/2 [SAM: Color preset (0 - normal/1 - warm/2 - cool)]
Control 0xe1: +/1/1 [SAM: Power control (0 - off/1 - on)]
Control 0xe2: +/0/1 [???]
Control 0xed: +/108/255 [SAM: Red Video Black Level]
Control 0xee: +/101/255 [SAM: Green Video Black Level]
Control 0xef: +/103/255 [SAM: Blue Video Black Level]
一个有趣的问题是您的监视器是否返回该数据，如果不是，它是否会响应，如果它当前关闭。
