Title: Bootloop with a RTX 4070 on Debian with GNOME
Date: 2023-07-28 23:00

Thanks to fortunate circumstances,
I became the owner of an [Nvidia GeForce RTX 4070](https://www.nvidia.com/en-us/geforce/graphics-cards/40-series/rtx-4070-4070ti/):
[DLSS](https://en.wikipedia.org/wiki/Deep_learning_super_sampling), [ray tracing](https://en.wikipedia.org/wiki/Ray_tracing_(graphics)), better power efficiency, …
I can hang out with the gamers now!
Unfortunately, on my Debian Sid with [GNOME](http://gnome.org/), the GPU is too recent for [nouveau](https://nouveau.freedesktop.org/) to work,
and the
garbage/secure-boot-breaking/binary-blob/[fuck-you-nvidia](https://arstechnica.com/information-technology/2012/06/linus-torvalds-says-f-k-you-to-nvidia/)
[proprietary drivers](https://wiki.debian.org/NvidiaGraphicsDrivers) leads to a bootloop.

Somewhere hidden in the huge syslog, one can see the following:

```logs
2023-07-28T19:16:38.600949+02:00 facilier /usr/libexec/gdm-x-session[1573]: /etc/gdm3/Xsession: Beginning session setup...
2023-07-28T19:16:38.611970+02:00 facilier /usr/libexec/gdm-x-session[1584]: dbus-update-activation-environment: setting DBUS_SESSION_BUS_ADDRESS=unix:path=/run/user/1000/bus
2023-07-28T19:16:38.611994+02:00 facilier /usr/libexec/gdm-x-session[1584]: dbus-update-activation-environment: setting DISPLAY=:0
2023-07-28T19:16:38.612010+02:00 facilier /usr/libexec/gdm-x-session[1584]: dbus-update-activation-environment: setting XAUTHORITY=/X11/Xauthority
2023-07-28T19:16:38.612554+02:00 facilier dbus-daemon[1115]: [system] Successfully activated service 'org.freedesktop.UPower'
2023-07-28T19:16:38.612678+02:00 facilier systemd[1]: Started upower.service - Daemon for power management.
2023-07-28T19:16:38.615580+02:00 facilier /usr/libexec/gdm-x-session[1587]: Authorization required, but no authorization protocol specified
2023-07-28T19:16:38.615619+02:00 facilier /usr/libexec/gdm-x-session[1587]: xrdb: Resource temporarily unavailable
2023-07-28T19:16:38.615636+02:00 facilier /usr/libexec/gdm-x-session[1587]: xrdb: Can't open display ':0'
2023-07-28T19:16:38.618702+02:00 facilier /usr/libexec/gdm-x-session[1594]: Authorization required, but no authorization protocol specified
2023-07-28T19:16:38.618727+02:00 facilier /usr/libexec/gdm-x-session[1594]: xhost:  unable to open display ":0"
2023-07-28T19:16:38.685466+02:00 facilier gnome-session[1573]: gnome-session-binary[1573]: WARNING: software acceleration check failed: Child process exited with code 1
2023-07-28T19:16:38.685489+02:00 facilier gnome-session-binary[1573]: WARNING: software acceleration check failed: Child process exited with code 1
2023-07-28T19:16:38.692650+02:00 facilier gnome-session[1617]: Authorization required, but no authorization protocol specified
2023-07-28T19:16:38.692909+02:00 facilier gnome-session-f[1617]: Cannot open display:
```

The interesting part being `software acceleration check failed`, from
`gnome-session`, as well as `gdm-x-session`. I have automatic login, so it seems that 
[GDM](https://wiki.gnome.org/Projects/GDM) is launching an [X](https://www.x.org/wiki/) session instead of
a [Wayland](https://wayland.freedesktop.org/) one, and gnome-session falls over trying to use hardware acceleration
there.

Looking at GDM's source code, and searching for `wayland` leads to a property called
[`WaylandEnabled`](https://gitlab.gnome.org/search?search=WaylandEnable&nav_source=navbar&project_id=1856&group_id=8&search_code=true&repository_ref=main),
used in a couple of places, including [`/lib/udev/rules.d/61-gdm.rules`](https://gitlab.gnome.org/GNOME/gdm/-/blob/main/data/61-gdm.rules.in),
where it can be automatically disabled should some [udev](https://en.wikipedia.org/wiki/Udev) rules match.

Getting rid of the bootloop is simply a matter of commenting the two `RUN` lines telling GDM to prefer Xorg and to disable Wayland:

```ini
LABEL="gdm_prefer_xorg"
#RUN+="/usr/libexec/gdm-runtime-config set daemon PreferredDisplayServer xorg"
GOTO="gdm_end"

LABEL="gdm_disable_wayland"
#RUN+="/usr/libexec/gdm-runtime-config set daemon WaylandEnable false"
GOTO="gdm_end"
```

A proper fix would be of course to make GDM properly detect that the GPU
supports Wayland with hardware acceleration, but I wasted enough time on it
already, and I __really__ don't want to
touch anything display/Xorg related anymore, ever. I still have PTSD from
trying to write a Xorg.conf by hand, 15 years ago.