No display found with ddcutil on Jetson Orin Nano

Autonomous Machines Jetson & Embedded Systems Jetson Orin Nano
1

I checked that the monitor supports ddc control and had success in controlling from other linux desktops.
When I input command “ddcutil detect -verbose” No display found returns.

I am using a passive dp to hdmi adapter to connect to the hdmi monitor I want to control. Should I use an “active” dp to hdmi adapter? Anyone had any luck with controlling their monitor with ddcutil on the Jetson Orin Nano?

2

Most GPUs you look at with this are PCIe. This means they are discrete GPUs (dGPU). Jetsons have a GPU which is directly integrated to the memory controller (an iGPU), and so some access, if using a standardized PCI function, don’t work on Jetsons. I can’t say for certain that this is the case, but it probably is.

If you just want to read the EDID, then what do you see from:
find /sys -name 'edid'

For each file found, cd to its location, and “cat edid” to see the content. This is directly from the driver, and is not something you can change by writing to it. One difference you will find between the iGPUs and dGPUs is that they configure only via EDID, and something xrandr can switch between modes, but cannot change to a mode which is not part of the EDID.

3

Thanks for your reply. If I want to control using tools like ddcutil, you are saying that it might not work as it is a Jetson GPU is a iGPU?

4

That is correct. It isn’t guaranteed, but it is highly likely that any generic GPU query tool uses a PCI bus query. However, if the query is from the “/sys” content (which is populated by the driver), then it should still work. The trouble with “/sys” content is that it tends to be variable depending on the driver; thus the more common case of trying to use a PCI query.

Incidentally, both DisplayPort and HDMI have a DDC wire, and this is what communicates the EDID (using an i2c protocol). A passive adapter between HDMI and DisplayPort is not an issue. The place where people get in trouble is with a passive adapter to VGA (which does not have DDC) or analog DVI (only digital DVI has DDC).

5

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