DIY IPMI fans

It was pointed out on the Raptor discussion board that the ibmpowernv hwmon module doesn't report fan speed for Raptor family systems, and I suspect this is true for most things based on the Romulus reference design (you can only see the fan of the graphics card, and of course only if it's installed). This means most of the GNOME shell extensions to display system status won't display it. However, it is accessible by talking to the BMC over IPMI, so you should be able to get it that way. Here's a quick-and-dirty method to put your Blackbird or T2 fan speed(s) into your GNOME shell (and probably works fine for other systems with IPMI-accessible fans). This is using Fedora 31; adjust for your distro to taste.

1. First, verify that you do have fans. You'll need to do this as root: sudo ipmitool sdr type fan

   This will show output like this, after a couple seconds:

   fan0   | DDh | ok  | 29.1 | 2100 revolution
   fan1   | DEh | ok  | 29.2 | 2100 revolution
   fan2   | DFh | ok  | 29.3 | 1900 revolution
   fan3   | E2h | ok  | 29.4 | 2000 revolution
   fan4   | E3h | ok  | 29.5 | 1700 revolution
   fan5   | E4h | ok  | 29.6 | 1700 revolution
   fan6   | E5h | ns  | 29.7 | Disabled
   

2. We don't want to have to constantly query the BMC as root, so create a ipmi group and put yourself in it (with vigr, vigr -s and vipw as needed). Log out and log back in, and check groups to make sure you have ipmi privileges.

3. Create a udev rule to make IPMI group-accessible by our new group ipmi. In /etc/udev/rules.d/99_my.rules, I have

   # allow ipmi to be seen by ipmi group
   KERNEL=="ipmi*", GROUP="ipmi", MODE="0660"

   Restart your system to make sure this sticks, and/or chgrp ipmi /dev/ipmi0 ; chmod 0660 /dev/ipmi0 to make the change live. You should now be able to just do ipmitool sdr type fan as your IPMI-group user.

Now that your system is configured, let's actually integrate the output. At some point I'll maybe make this into a full-fledged extension but for prototyping and playing around purposes, there is an easier way: Argos. Though sadly the maintainer is no longer a GNOME user, the extension seems to work fine still for this purpose as of this writing.

1. Install the Argos GNOME extension if not already done. You may wish to chmod -x ~/.config/argos/argos.sh afterwards to get the demo menu out of your menu bar.

2. Download this simple script to format the output from ipmitool into Argos BitBar output. Its only dependencies are bash, awk and ipmitool. It gets the IPMI information, caches it (because it's expensive), and then figures out the fastest fan and puts that into the Argos button (click that for all the fans in the system, as shown in the screenshot).

3. The script goes into ~/.config/argos, but the filename will be based on where you want it and how quickly you want it to update itself. My filename is ipmitool.6r.5s.sh, which says set it to position six on the right side of the shell bar (this varies on other shell components you have there) and updates every 5 seconds.

4. Once you have selected position and interval, chmod +x ~/.config/argos/[filename].sh, Argos will automatically see it, and it will start updating at the interval encoded in the filename. If it's in the wrong place, or you don't like how quickly or slowly it updates, just rename the file and Argos will "do the right thing" live.