feat(ci): Add kernel module build and release workflow

Introduce a workflow to build kernel modules for multiple header packages on PRs and releases. PR builds verify compilation, while release builds package outputs and publish them to a Gitea release. This enhances automation and ensures compatibility across target environments.

.gitea/workflows/build-kernel.yml

@@ -0,0 +1,92 @@
+name: Build kernel module
+
+on:
+  # Release flow: triggered when a version tag is pushed (tag a commit on master).
+  # Builds every target and publishes the modules to a Gitea release.
+  push:
+    tags:
+      - 'v*'
+  # Compile-check flow: every PR that targets master. Builds only, no release.
+  pull_request:
+    branches:
+      - master
+
+jobs:
+  # Build (and thereby compile-check) the module for each header package. Runs on
+  # both triggers — on a PR this is the whole story; on a tag the `release` job
+  # below consumes the artifacts. All packages build against the latest archive
+  # kernel; the exact version is auto-resolved from the image at build time.
+  build:
+    runs-on: ubuntu-latest
+    strategy:
+      # Don't cancel the other targets if one package fails to build.
+      fail-fast: false
+      matrix:
+        headers_pkg:
+          - linux-headers-rpi-v8   # 64-bit (Pi Zero 2 W)
+          - linux-headers-rpi-v7   # 32-bit
+          - linux-headers-rpi-v6   # 32-bit (older Pis)
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Build module (${{ matrix.headers_pkg }})
+        working-directory: kernel
+        env:
+          HEADERS_PKG: ${{ matrix.headers_pkg }}
+        run: ./build-in-docker.sh
+
+      - name: Stage build output (<kernel_version>/<headers_pkg>.ko)
+        working-directory: kernel
+        run: |
+          # Ask the just-built image which kernel tree it installed, then drop the
+          # -rpi-vN arch suffix so every package shares one version folder.
+          kver=$(docker run --rm --platform linux/arm64 --entrypoint sh \
+                   "${IMAGE:-iec-kbuild}" -c 'ls -1 /lib/modules | sort -V | tail -n1')
+          ver="${kver%-rpi-*}"
+          echo "resolved kernel: $kver -> version folder: $ver"
+          mkdir -p "out/$ver"
+          mv iec_listener.ko "out/$ver/${{ matrix.headers_pkg }}.ko"
+
+      - name: Upload build output
+        uses: actions/upload-artifact@v4
+        with:
+          # Name by headers_pkg so artifact names stay unique; the shared
+          # <kernel_version>/ folder is reassembled at download via merge-multiple.
+          name: ${{ matrix.headers_pkg }}
+          path: kernel/out
+          if-no-files-found: error
+
+  # Release flow only: reassembles the <kernel_version>/ folders, wraps them in a
+  # single repo-named top folder alongside selftest.sh, zips it and attaches it to
+  # the Gitea release for the pushed tag. Skipped entirely on pull requests.
+  release:
+    needs: build
+    if: startsWith(github.ref, 'refs/tags/')
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Download all build output
+        uses: actions/download-artifact@v4
+        with:
+          path: modules
+          # Merge every artifact back into the shared <kernel_version>/ tree.
+          merge-multiple: true
+
+      - name: Assemble release package
+        run: |
+          repo="${{ github.event.repository.name }}"
+          root="package/$repo"
+          mkdir -p "$root"
+          cp -r modules/. "$root"/          # <kernel_version>/<headers_pkg>.ko
+          cp kernel/selftest.sh "$root"/    # selftest.sh only at the package root
+          (cd package && zip -r "../${repo}-${{ github.ref_name }}.zip" "$repo")
+
+      - name: Publish to Gitea release
+        uses: actions/gitea-release-action@v1.3.6
+        with:
+          api_key: ${{ secrets.GITEA_TOKEN }}
+          files: |-
+            *.zip