How can I modify dmidecode information

Autonomous Machines Jetson & Embedded Systems Jetson Orin NX
1

Hi Nvidia,

We want to display custom information on dmidecode of L4T35.4.1.
(just like vender, board id, system version…)
Do I modify uefi file or other files?
Thanks help.

2

I can’t answer, but I’ll get you started.

Normally Jetson drivers only accept EDID data for setup. Other information tends to be ignored (desktops have more flexibility with this). That setup is expected via the DDC wire on the HDMI or DisplayPort upon hotplug detect. The normal setup which is available is only to pick which mode of the EDID which is to be used rather than specifying modes which are not in EDID.

Video drivers do have a fallback mode though. If EDID is not present, then a mode is chosen. I’m not sure where it is in the kernel, but sometimes people do set up the fallback mode to be a custom EDID they have placed in the kernel. If you want to see what EDID a given monitor is viewed as having, then you can check:

sudo find /sys -name 'edid'

In order to know what the driver actually thinks of that EDID (not all modes are supported sometimes) you would add this to your “/etc/X11/xorg.conf” section “Device”:

Section "Device"
   Option "ModeDebug"
...

Then, if you know your “$DISPLAY” (which is usually “:0”, but only the “0” matters), you can get information in the “/var/log/Xorg.0.log” (if not “0” for “$DISPLAY” swap with that number) as to what the driver thinks of the EDID (such as being invalid checksum or valid), plus each mode will be commented on to say what is accepted or rejected (and if rejected it might say why).

The file in the kernel to look at is named “edid.c”. I’m not sure of the details, and things have probably changed going from a 4.x kernel to a 5.x kernel, but generally speaking there is a section on “dc” (subdirectory name) for “display controller”. Some of that is out-of-tree, some is in tree. If you have the NVIDIA source, then there is a “kernel/nvidia/” subdirectory and a “kernel/kernel-5.10/” subdirectory for R35.x. If you cd to the location with both the “nvidia/” and “kernel/” subdirectories, try this search:
find . -type d -name 'dc'

That will get you started.

Also, be sure to check your EDID in http://www.edidreader.com.

3

Hi @linuxdev ,

Thanks reply,
But we want to modify DMI information, not EDID.

4

That’s one I cannot answer.

5

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