docs: nvidia/: TODO, research and test instructions for the NVIDIA fix (moved here from the steamify-cachyos branch); AGENTS.md: feature notes live in this repo

nvidia/TODO.md

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+# TODO: NVIDIA fix for gaming mode
+
+Product code: branch `feature/nvidia-gaming-fix` in steamify-cachyos (github.com/theupriser/steamify-cachyos). These notes live here, in
+steamify-cachyos-dev, on purpose: they are not part of the product and must not be in its history. The branch only has
+a `.no-release-yet` marker pointing here.
+
+When the feature is released, move what is still useful to steamify-cachyos' `TECHNICAL.md` and delete this folder (`nvidia/`).
+Written 2026-10-01 so a new session can pick this up.
+
+## Problem
+A PC with an NVIDIA RTX 5080 (Blackwell, open kernel modules) shows a corrupted
+image when gaming mode (gamescope) starts. Cause not confirmed. Steamify had no
+NVIDIA handling at all. Likely: `nvidia-drm.modeset=1` / `nvidia-drm.fbdev=1`
+missing, or a gamescope/driver mismatch.
+
+## What is built (all on the product branch, pushed)
+- `lib/nvidia.sh`: part of the SteamOS conversion (`gaming_enable` / `gaming_disable`).
+  With an NVIDIA GPU + driver it adds `nvidia-drm.modeset=1 nvidia-drm.fbdev=1` to the
+  kernel command line (Limine, systemd-boot, GRUB; backup first) and, only when every
+  installed kernel has `nvidia_drm`, `/etc/mkinitcpio.conf.d/90-steamify-nvidia.conf`.
+  Rebuilds initramfs + boot entries, verifies the config and the generated entries
+  have the parameters (error otherwise). Undone on disable. Description: `TECHNICAL.md`.
+- `FEATURE_VERSION[gaming]=2.9.7` so installs that already have the conversion re-apply it.
+- Test hooks `NVIDIA_DRM_DIR`, `NVIDIA_MODULES_DIR`, `NVIDIA_LIMINE_CONF`,
+  `NVIDIA_SDBOOT_DIR`, `NVIDIA_GRUB_CFG`: only set by tests; defaults are the real paths.
+
+## Tested
+- `bash tests/nvidia-test.sh`: 22 checks against a fake RTX 5080 beside an iGPU, a stub
+  `modinfo`, temp boot loader files. All pass.
+- Real VMs (QEMU/KVM, Limine, systemd-boot, GRUB): enable, reboot, kernel command line
+  has the parameters; disable, reboot, original command line. All pass. Found and fixed:
+  Limine pasted an appended `+=` line as text into the cmdline; a kernel without the
+  NVIDIA modules made limine-mkinitcpio skip its boot entry.
+
+## Kernel changes (done, VM-tested 2026-10-01, Limine)
+The early-load drop-in is kept right by a pacman hook (`patches/steamify-nvidia-initramfs.{sh,hook}`,
+installed by `nvidia_enable`, `/etc/pacman.d/hooks/85-steamify-nvidia-initramfs.hook`). Real pacman
+transactions in a Limine VM: the hook runs between "Updating module dependencies" and "Updating
+linux initcpios" (real hook names there: 60-*-remove, 80-limine-efi-deploy, 90-limine-mkinitcpio-remove-post,
+90-mkinitcpio-install; DKMS would be 71-): the drop-in is present while every kernel has the modules, removed
+when the LTS kernel loses them, back when they return; initramfs nvidia files 1 -> 5 -> 1 -> 5 -> 1
+(1 = baseline, 4 modules added); no ERROR/skipping in any rebuild; cmdline kept the parameters after a reboot;
+disable removes hook, script and drop-in. Found on the way: an empty hook/script was installed when
+`patch_file` failed (now an error). Only tested with fake modules (renamed copies of a small module), on
+Limine; systemd-boot and GRUB use the same hook but were not run with pacman transactions.
+
+## Opt-out toggle (new request, 2026-10-01: not built yet)
+When a compatible NVIDIA card is listed there should be a menu option, on by default (opt-out), named
+"NVIDIA compatibility", as a sub-option of the SteamOS conversion, directly under "Boot into" (`boot`).
+Today the fix runs unconditionally inside `gaming_enable`/`gaming_disable`.
+- [ ] New component `nvidia` in `lib/menu.sh`: `COMPONENTS` right after `boot`, `PARENT[nvidia]=gaming`, `LABEL`,
+      `FEATURE_VERSION[nvidia]`, `component_available` -> `nvidia_available` (= `nvidia_present`); not in
+      `NO_PRESELECT` (ticked by default, `feature_new` ticks it for installs that already have the conversion).
+      `nvidia_status` from the system (hook + parameters present), `nvidia_enable`/`nvidia_disable` = the code now
+      called from `gaming_enable`/`gaming_disable` (remove those calls). Check `toggle_component` dependencies,
+      `feature_record_unticked`, the plan texts ("This will: ...").
+- [ ] The app: `ui/qml/Texts.qml` item texts, `AppState.qml`, the screen rows, `lib/backend.sh` if it lists ids;
+      `--defaults [--options <ids>]` (the Steam Machine ISO's installer pages: it names the ids) and `--skip`.
+- [ ] README rows/screenshot rule (a release that adds a menu row retakes `assets/screenshot-menu.png`), TECHNICAL.md,
+      CHANGELOG, `tests/nvidia-test.sh` (status/enable/disable through the component), VM menu test in
+      steamify-cachyos-dev (`share/vmtest/menu`, TESTPLAN.md row).
+- [x] What "compatible" means (decided 2026-10-01): RTX 20 series or newer, the same check as the VRAM booster
+      (`vram_nvidia_legacy_id`: a card on chwd's legacy lists `/var/lib/chwd/ids/nvidia-*.ids` is older; without the
+      lists every card counts). `nvidia_present` = such a card + `nvidia_drm` available; the toggle's `nvidia_available`
+      is the same function. Older cards (GTX 10/9 series) are left alone: no promise they work with gamescope.
+
+## Older cards and other research
+Decision 2026-10-01: support RTX 20 series or newer only, with the VRAM booster's check (done in `lib/nvidia.sh`).
+The user had hoped older GPUs would work too; not promised. Full notes with sources: **`nvidia/RESEARCH.md`**.
+Short version: open kernel modules need Turing+, Maxwell/Pascal/Volta need the proprietary driver (580 legacy branch);
+`nvidia-drm.modeset/fbdev` exist in both, so the fix applies to any card with `nvidia_drm`, but nothing found says gamescope
+works better or worse there (a GTX 1050 Ti has a known gamescope>3.16.16 start problem on HDMI, not ours). Cannot be promised:
+needs a test on a real older card. Design for the toggle: on by default for any card with `nvidia_drm`, the label says
+what it does, `tests/nvidia-hardware-test.sh` reports GPU and driver so results can be compared.
+
+## Still to do
+1. [ ] **On the NVIDIA PC** (only place the real fix can be judged; the full steps, how to read the results and the undo
+   are in `nvidia/INSTRUCTIONS.md`), from the steamify-cachyos checkout on that branch:
+   `bash tests/nvidia-hardware-test.sh check` (before), `... apply` (asks sudo), reboot,
+   `... check` (after: `nvidia_drm modeset/fbdev = Y`), boot gaming mode, then
+   `... visual` (was the picture clean?). Everything goes to `~/steamify-nvidia-report.txt`:
+   paste it into the session.
+2. [ ] If the parameters apply but the picture is still corrupted: look at the report's
+   gamescope/NVIDIA log lines and the versions (`nvidia-open`, `nvidia-utils`, `gamescope`,
+   `gamescope-session-cachyos`); the cause is then probably a gamescope/driver mismatch
+   for Blackwell, not this fix.
+3. [ ] Not covered by any test: the early-load drop-in with the REAL NVIDIA modules (the VMs only have renamed
+   fake ones), and systemd-boot/GRUB with a pacman transaction (only Limine was run).
+4. [ ] **Verify the RTX 20+ check on the PC** (decided 2026-10-01, only unit-tested with a fake chwd list; this laptop and the VMs
+   have no `/var/lib/chwd/ids`): `bash tests/nvidia-hardware-test.sh check` prints the NVIDIA PCI id, whether it is on a chwd legacy
+   list, and whether the lists exist at all. Expect for the RTX 5080: "supported", "not on a legacy list". If it says "no chwd
+   legacy lists found" the check cannot tell old from new there (every card then counts as supported, like the VRAM booster):
+   look at what `chwd`/`/var/lib/chwd/ids` provide on CachyOS and whether another source (the open-driver device list, the
+   `nvidia-open` package) would be better for both the VRAM booster and this fix. Also try `check` on any older NVIDIA card
+   that turns up (GTX 10/9 series): it must say "older than RTX 20 ... not applied" and `apply` must change nothing.
+5. [ ] Changelog: fill in the commit hashes of this feature's lines (next commit, per AGENTS.md).
+6. [ ] Build the opt-out toggle (section above) before release.
+7. [ ] When complete and tested: ask the user whether it may be released. On a yes delete
+   `.no-release-yet` (and this folder in the dev repo), open the PR into `release/2.9.7` (local branch only so
+   far, one commit `chore: Version 2.9.7`; push it then) and merge it. The user merges
+   `release/2.9.7` into `main`.
+
+## Working rules (steamify-cachyos `AGENTS.md` and this repo's `AGENTS.md`)
+- Never work on `main` or a `release/*` branch; no `Co-Authored-By` / "Generated with
+  Claude" lines in commits or PRs. No git identity on the dev laptop: use
+  `git -c user.name="Rick Peters" -c user.email="rickpeters@upriser.nl" commit`.
+- Don't push `release/2.9.7` before the PR (a push can start a dev ISO build).
+
+## If the VM tests need repeating (dev laptop, Ubuntu)
+- `scripts/vminstall.sh` (steamify-cachyos-dev) with `VM_BOOTLOADER=limine|systemd-boot|grub`,
+  `CI=1`, a short `VM_DIR` (`~/vms/...`: socket paths over 108 bytes fail) and `VM_SSH_KEY`.
+- This session's shell lacked the `kvm` group: run QEMU steps as `sg kvm -c "..."`.
+- `/tmp/vminstall-iso.lock` belongs to another user and there is no `bsdtar`: use a copy of
+  `vminstall.sh` with another lock path and a `bsdtar` shim (Python `pycdlib` in a venv).
+- Delete everything afterwards (`~/vms` incl. `pkg-cache`, the 3 GB ISO, keys).