Add CM5 support: ubuntu-24.04-arm runner, extensions, workflow improvements, README updates

README.md

@@ -1,7 +1,9 @@
 # Raspberry Pi 5 Talos Builder
-This repository serves as the glue to build custom Talos images for the Raspberry Pi 5. It patches the Kernel and Talos build process to use the Linux Kernel source provided by [raspberrypi/linux](https://github.com/raspberrypi/linux). 
+
+This repository serves as the glue to build custom Talos images for the Raspberry Pi 5. It patches the Kernel and Talos build process to use the Linux Kernel source provided by [raspberrypi/linux](https://github.com/raspberrypi/linux).
 
 ## Tested on
+
 So far, this release has been verified on:
 
 | ✅ Hardware                                                |
@@ -11,30 +13,49 @@ So far, this release has been verified on:
 | Raspberry Pi 5b with [RS-P11 for RS-P22 RPi5](https://wiki.52pi.com/index.php?title=EP-0234) |
 
 ## What's not working?
+
 * Booting from USB: USB is only available once LINUX has booted up but not in U-Boot.
 
 ## How to use?
-The releases on this repository align with the corresponding Talos version. There is a raw disk image (initial setup) and an installer image (upgrades) provided. 
+
+The releases on this repository align with the corresponding Talos version. There is a raw disk image (initial setup) and an installer image (upgrades) provided.
 
 ### Examples
+
 Initial:
-```
+
+```bash
 unzstd metal-arm64-rpi.raw.zst
 dd if=metal-arm64-rpi.raw of=<disk> bs=4M status=progress
 sync
 ```
 
 Upgrade:
-```
+
+```bash
 talosctl upgrade \
   --nodes <node IP> \
   --image ghcr.io/talos-rpi5/installer:<version>
 ```
 
 ## Building
+
+### Using GitHub Actions
+
+The CI workflow builds and publishes images automatically. It can be triggered two ways:
+
+- **Push a tag** matching `v*.*.*` — this triggers the full build and creates a GitHub Release:
+  ```bash
+  git tag v1.11.5-cm5
+  git push origin v1.11.5-cm5
+  ```
+- **Manual run** — go to Actions → build → "Run workflow" to trigger a build without creating a release.
+
+### Local build
+
 If you'd like to make modifications, it is possible to create your own build. Bellow is an example of the standard build.
 
-```
+```bash
 # Clones all dependencies and applies the necessary patches
 make checkouts patches
 
@@ -48,5 +69,45 @@ make REGISTRY=ghcr.io REGISTRY_USERNAME=<username> overlay
 make REGISTRY=ghcr.io REGISTRY_USERNAME=<username> installer
 ```
 
+### Extensions support
+
+Talos [system extensions](https://www.talos.dev/latest/talos-guides/configuration/system-extensions/) can be baked into the installer image at build time.
+
+**Makefile variables:**
+
+```makefile
+EXTENSIONS ?=
+EXTENSION_ARGS = $(foreach ext,$(EXTENSIONS),--system-extension-image $(ext))
+```
+
+`EXTENSIONS` is a space-separated list of `image:tag@sha256:digest` references passed as a make variable at build time — no Makefile edits needed. Internally, the Makefile expands each entry into a `--system-extension-image` flag and passes them all to the Talos imager.
+
+**Adding extensions to the CI build:**
+
+Just add a new `EXTENSION_*` env var at the top of `.github/workflows/build.yaml` — the digest resolution step automatically loops through all vars matching that prefix:
+
+```yaml
+env:
+  EXTENSION_ISCSI_IMAGE: ghcr.io/siderolabs/iscsi-tools:v0.2.0
+  EXTENSION_UTIL_LINUX_IMAGE: ghcr.io/siderolabs/util-linux-tools:2.41.2
+  EXTENSION_MY_IMAGE: ghcr.io/siderolabs/my-extension:v1.0.0   # ← just add this
+```
+
+The workflow resolves the digest for each at build time and assembles the full `EXTENSIONS` string automatically.
+
+**Adding extensions for a local build:**
+
+```bash
+# Resolve the digest first
+DIGEST=$(crane digest ghcr.io/siderolabs/foo-extension:v1.0.0)
+
+make REGISTRY=ghcr.io REGISTRY_USERNAME=<username> \
+  EXTENSIONS="ghcr.io/siderolabs/foo-extension:v1.0.0@${DIGEST}" \
+  installer-pi5
+```
+
+Pass multiple extensions as a space-separated string inside the quotes.
+
 ## License
+
 See [LICENSE](LICENSE).