LinuxQuestions.org - RedHat Detecting Monitor Status

- Linux - Hardware (https://www.linuxquestions.org/questions/linux-hardware-18/)

- - RedHat Detecting Monitor Status (https://www.linuxquestions.org/questions/linux-hardware-18/redhat-detecting-monitor-status-733041/)

RedHat Detecting Monitor Status

Hello all,

I am new to Red Hat Enterprise 5. I am trying to figure out whether the monitor attached to the machine is attached to a power source or not. I have tried xrandr, and the output is below, but I don't see any difference between whether the system's monitor is on or not. I have tried using sense codes and ddcprobe, but my version of Linux does not even recognize ddcprobe, and I am not allowed to add anything to the system other than what is available, and what I can get approved. If anyone has any commands that might get me the information I need, I would greatly appreciate it, thank you.

SZ: Pixels Physical Refresh
0 1024 x 768 ( 347mm x 260mm ) 85 75 70 60 0
1 832 x 624 ( 281mm x 211mm ) 75
2 800 x 600 ( 271mm x 203mm ) 85 75 72 60 56 0
3 640 x 480 ( 216mm x 162mm ) 85 75 73 60 0
4 720 x 400 ( 243mm x 135mm ) 85
5 640 x 400 ( 216mm x 135mm ) 85 0
6 640 x 350 ( 216mm x 118mm ) 85
7 320 x 240 ( 108mm x 81mm ) 0
8 400 x 300 ( 135mm x 101mm ) 0
9 512 x 384 ( 173mm x 130mm ) 0
10 1152 x 864 ( 390mm x 292mm ) 0
11 1280 x 960 ( 433mm x 325mm ) 0
12 1400 x 1050 ( 474mm x 355mm ) 0
13 1600 x 1200 ( 542mm x 406mm ) 0
14 1920 x 1440 ( 650mm x 487mm ) 0
15 2048 x 1536 ( 694mm x 520mm ) 0
16 854 x 480 ( 289mm x 162mm ) 0
17 1280 x 720 ( 433mm x 243mm ) 0
18 1366 x 768 ( 462mm x 260mm ) 0
19 1920 x 1080 ( 650mm x 365mm ) 0
20 1280 x 800 ( 433mm x 270mm ) 0
21 1440 x 900 ( 487mm x 304mm ) 0
22 1680 x 1050 ( 569mm x 355mm ) 0
23 1920 x 1200 ( 650mm x 406mm ) 0
24 720 x 480 ( 243mm x 162mm ) 0
25 720 x 576 ( 243mm x 195mm ) 0
26 320 x 200 ( 108mm x 67mm ) 0
27 800 x 480 ( 271mm x 162mm ) 0
28 1280 x 768 ( 433mm x 260mm ) 0
29 1280 x 1024 ( 433mm x 346mm ) 0
30 2360 x 1770 ( 799mm x 599mm ) 0
*31 1076 x 874 ( 364mm x 295mm ) *0
Current rotation - normal
Current reflection - none
Rotations possible - normal
Reflections possible - none

Quote:

Originally Posted by davidov541

I am trying to figure out whether the monitor attached to the machine is attached to a power source or not.

Are you unable to physically view the machine & monitor?

Are you querying for the EDID? If so it may not matter if the monitor is powered off...

Quote:

Providing +5 volts allows the DDC circuit in the monitor to remain active even when the monitor itself is powered off. Ref.: Section 4.1.4.1

So if the card is provided +5v like it should... then you're still going to be able to query the monitor and get an answer.

Quote:

Q: What are the intended uses for the +5V output?

A: +5V is needed as a power source for the DDC and EDID circuits of a display monitor when the host is attempting to read the monitor's EDID data and the monitor's own local power supply is not yet turned on.

Both quotes come from http://vesa.org/FAQ/standardsFAQ.htm

I guess I need to clairify a little as to what I'm trying to do. I have a power strip set up such that I can turn on or off the power to any of the outlets programmatically through my C++ program. I am writing a program which will toggle each outlet one by one, and verify that the device that should be plugged in into that outlet (and thus should have one less power source when the outlet is off) is the right one. In order to do this with the monitor, I need some way of detecting when I turn off the power to the monitor, that the monitor has no power (since it is not backed up like the other devices are). Hopefully that clears things up.