Document what I did on Asahi Linux

This... isn't really a true guide. I'm documenting what I did so
that it doesn't get lost elsewhere.

I did all my testing with this with a dummy monado profile,
but it would likely be *much* more useful to try this with
wivrn and a wireless headset, and I may try to arrange
circumstances where I can test it.

content/Asahi_Linux.md

@@ -0,0 +1,80 @@
+---
+title: Asahi Linux
+---
+
+# Asahi Linux
+
+*AKA: Fedora on aarch64 with extra steps*
+
+## Envision
+
+Fedora has the `envision` package, as well as the `envision-monado` and `envision-wivrn` metapackages which grab the necessary dependencies for building monado and wivrn, respectively.
+This *will not* be the most up-to-date with upstream envision, but seeing as Envision doesn't currently build aarch64 AppImages, this is the easiest way to build custom commits of monado/wivrn/opencomposite/xrizer.
+
+## Multiarch
+
+Depending on what openxr applications you are planning on running, you may need multiple builds of the same component, but for different architectures.
+I will refer to the components as monado and opencomposite going forward, but the same information holds for wivrn and xrizer.
+
+Here's how I created an environment that can run both aarch64 openxr/openvr applications, and x86_64 openxr/openvr applications:
+
+I started by using envision on an aarch64 machine and an x86_64 machine, building the same profile on the same commits.
+Each prefix (containing monado) was copied from `~/.local/share/envision/prefixes/{profile id}/` to a directory on my Asahi Linux install.
+(In my case, `~/multiarch_monado/monado-x86_64-prefix/` and `~/multiarch_monado/monado-aarch64-prefix/`.)
+The two instances of OpenComposite (located at `~/.local/share/envision/{profile id}/OpenComposite/build`) should be merged into a single directory.
+(In my case, `~/multiarch_monado/opencomposite`.)
+The x86_64 build of OpenComposite should contribute `bin/linux64/vrclient.so`, while the aarch64 build of OpenComposite should contribute `bin/linuxarm64/vrclient.so`.
+(If you are following along using an OpenComposite commit that pre-dates <https://gitlab.com/znixian/OpenOVR/-/merge_requests/179>,
+or an xrizer commit that pre-dates <https://github.com/Supreeeme/xrizer/pull/106>,
+you should rename the `bin/linux64` folder from the aarch64 build to `bin/linuxarm64`.
+Or you can choose to ignore the aarch64 build entirely, since Steam games don't currently require it.)
+
+Runtimes that have been copied from another machine should probably be setcap'd: `sudo setcap CAP_SYS_NICE=eip monado-service`
+
+To be able to run openxr applications, we need to create the symlinks `active_runtime.x86_64.json` and `active_runtime.aarch64.json` in `~/.config/openxr/1/`.
+On my machine, this looks like:
+```sh
+ln -s ~/multiarch_monado/monado-aarch64-prefix/share/openxr/1/openxr_monado.json ~/.config/openxr/1/active_runtime.aarch64.json
+ln -s ~/multiarch_monado/monado-x86_64-prefix/share/openxr/1/openxr_monado.json ~/.config/openxr/1/active_runtime.x86_64.json
+```
+
+To be able to run openvr applications, we need to create `~/.config/openvr/openvrpaths.vrpath`.
+This is overridden when you start steam in some cases, so make sure you keep an extra copy handy to re-override it.
+On my machine, the contents of `openvrpaths.vrpath` is as follows:
+```
+{
+        "jsonid": "vrpathreg",
+        "runtime": [
+                "/home/kitlith/multiarch_monado/opencomposite"
+        ],
+        "version": 1
+}
+```
+
+## Steam Games under muvm
+
+What worked for me was running `monado-service` manually, with all the environment variables that envision uses, and manually setting up environment variables for steam launch arguments.
+On my machine, the launch arguments look like: `PRESSURE_VESSEL_FILESYSTEMS_RW=/run/user/1000/monado_comp_ipc XR_RUNTIME_JSON=~/.config/openxr/1/active_runtime.x86_64.json %command%`
+There is some extra complication caused my muvm putting its `XDG_RUNTIME_DIR` in a weird spot interfering with monado's ability to connect to itself.
+Therefore, my reccomended launch order is as follows:
+
+Launch steam from inside a terminal (so that you can see logs when things inevitably work incorrectly):
+```sh
+steam
+```
+
+Lanuch monado-service:
+```sh
+muvm -it -- bash
+```
+
+```sh
+mkdir -p /run/user/1000/
+chmod 700 /run/user/1000/
+# setup the rest of the environment variables, ensuring XRT_DEBUG_UI is *not* enabled.
+XDG_RUNTIME_DIR=/run/user/1000/ ./monado-service
+```
+
+Ensure that `openvrpaths.vrpath` has the correct contents and hasn't been overwritten by steam.
+
+Launch a game.