fix(kernel): Use per-version tags in Docker build to isolate jobs

Prevent race conditions in concurrent job builds by introducing unique
Docker image tags per kernel version. This ensures isolated builds with
correct verm

.gitea/workflows/build-kernel.yml

@@ -51,23 +51,31 @@ jobs:
           if [ ! -e /proc/sys/fs/binfmt_misc/qemu-aarch64 ]; then
             docker run --privileged --rm tonistiigi/binfmt --install arm64
           fi
+          # Per-version image tag. The matrix entries can run concurrently on a
+          # single runner sharing one Docker daemon; a fixed tag (e.g. iec-kbuild)
+          # is then a shared mutable name and the builds race — whichever `docker
+          # build` finishes last wins the tag, so both `docker create` calls
+          # resolve to the same image and every job emits the same vermagic.
+          # A unique tag per kernel version isolates them.
+          img="iec-kbuild:${KERNEL_VERSION//[:\/]/-}"
           # Builder image: toolchain + matching raspberrypi kernel headers.
           docker build --platform linux/arm64 \
             --build-arg DEBIAN_SUITE="$DEBIAN_SUITE" \
             --build-arg HEADERS_PKG="$HEADERS_PKG" \
             --build-arg KERNEL_VERSION="$KERNEL_VERSION" \
-            -t iec-kbuild .
+            -t "$img" .
           # Compile inside the container. We use `docker cp` instead of the bind
           # mount that build-in-docker.sh uses for local builds: under the runner's
           # docker-in-docker, /workspace is a volume the host daemon can't see, so
           # `-v "$PWD:/build"` mounts an empty dir and make finds no Makefile.
-          cid=$(docker create --platform linux/arm64 --entrypoint sleep iec-kbuild infinity)
+          cid=$(docker create --platform linux/arm64 --entrypoint sleep "$img" infinity)
           docker start "$cid"
           docker cp ./. "$cid:/build"
           docker exec "$cid" /usr/local/bin/docker-entrypoint.sh clean
           docker exec "$cid" /usr/local/bin/docker-entrypoint.sh
           docker cp "$cid:/build/iec_listener.ko" ./iec_listener.ko
           docker rm -f "$cid"
+          docker rmi "$img" || true
 
       - name: Stage build output (modules/iec_listener_<kernel_version>.ko)
         working-directory: kernel

kernel/README.md

@@ -20,14 +20,35 @@ before connecting the real bus (see PLAN.md §10).
 ### Running it
 
 `selftest.sh` is non-persistent (nothing is installed into `/lib/modules`, no
-autoload): it checks vermagic, loads the module, runs the self-test, and always
-unloads it again.
+autoload): it detects the running kernel, picks the matching module, loads it,
+runs the self-test, and always unloads it again.
+
+A released package ships several kernel builds side by side:
+
+```
+comodore-iec-emu/
+├── selftest.sh
+└── modules/
+    ├── iec_listener_1-6.12.93-1+rpt1.ko   # built for 6.12.x (bookworm)
+    └── iec_listener_1-6.18.34-1+rpt1.ko   # built for 6.18.x (trixie)
+```
+
+You don't pick the file yourself: the script reads `uname -r`, then scans
+`modules/` (and a few fallback locations) and selects the `.ko` whose **vermagic**
+matches the running kernel. Matching is by vermagic rather than filename because
+the packaged name carries a Debian epoch/revision (`1:6.12.93-1+rpt1`) that
+`uname -r` (`6.12.93+rpt-rpi-v8`) does not.
 
 ```bash
-sudo ./selftest.sh                                # auto-finds ./ or ~/iec_listener.ko, address 4
-sudo ./selftest.sh ~/iec_listener.ko --address 5  # runs with ~/iec_listener.ko, address 5
+sudo ./selftest.sh                                # auto-selects the matching module, address 4
+sudo ./selftest.sh --address 5                    # same, address 5
+sudo ./selftest.sh ~/iec_listener.ko --address 5  # force a specific module file
 ```
 
+If no module matches the running kernel, the script lists the modules it found
+(with the kernel each was built for) and exits — rebuild for the current kernel,
+or pass a path explicitly.
+
 It exits non-zero unless the result is a full pass (`0x1F`), so it is usable in
 scripts/CI.
 

kernel/selftest.sh

@@ -62,13 +62,60 @@ done
 case "$ADDRESS" in ''|*[!0-9]*) die "address must be 0-30 (got '$ADDRESS')" ;; esac
 { [ "$ADDRESS" -ge 0 ] && [ "$ADDRESS" -le 30 ]; } || die "address out of range 0-30: $ADDRESS"
 
+command -v modinfo >/dev/null || die "modinfo not found (install kmod)"
+
+# ---- locate the module matching the running kernel ----------------------
+# A released package ships one module per supported kernel under modules/.
+# The build workflow names each file iec_listener_<kernel_version>.ko, with
+# ':' and '/' in the version replaced by '-' (1:6.12.93-1+rpt1 ->
+# iec_listener_1-6.12.93-1+rpt1.ko); local builds produce a bare
+# iec_listener.ko. The glob below ($MODULE*.ko) matches both.
+#
+# We select by vermagic, not by filename: the package name carries a Debian
+# epoch/revision (1:6.12.93-1+rpt1) that `uname -r` (6.12.93+rpt-rpi-v8) does
+# not, so the .ko whose vermagic matches the running kernel is the one to load.
+RUNNING="$(uname -r)"
+
+# Where to look, de-duplicated ($(dirname "$0") is often "." when run locally).
+SEARCH_DIRS=()
+for d in "$(dirname "$0")/modules" "$(dirname "$0")" "./modules" "." "$HOME"; do
+	skip=0
+	for s in "${SEARCH_DIRS[@]:-}"; do [ "$s" = "$d" ] && skip=1; done
+	[ "$skip" = 0 ] && SEARCH_DIRS+=("$d")
+done
+
 if [ -z "$KO" ]; then
-	for cand in "./${MODULE}.ko" "$HOME/${MODULE}.ko" "$(dirname "$0")/${MODULE}.ko"; do
-		[ -f "$cand" ] && { KO="$cand"; break; }
+	info "running kernel: $RUNNING"
+	for dir in "${SEARCH_DIRS[@]}"; do
+		[ -d "$dir" ] || continue
+		for cand in "$dir"/${MODULE}*.ko; do
+			[ -f "$cand" ] || continue
+			vm="$(modinfo -F vermagic "$cand" 2>/dev/null)" || continue
+			if [ "${vm%% *}" = "$RUNNING" ]; then
+				KO="$cand"; break 2
+			fi
+		done
 	done
 fi
-[ -n "$KO" ] && [ -f "$KO" ] || die "module not found; pass the path, e.g. sudo $0 ~/${MODULE}.ko"
-command -v modinfo >/dev/null || die "modinfo not found (install kmod)"
+
+if [ -z "$KO" ]; then
+	msg="no module matching the running kernel ($RUNNING) found.
+     Pass a path explicitly (sudo $0 path/to/${MODULE}.ko), or rebuild for
+     this kernel. Modules seen:"
+	any=0
+	for dir in "${SEARCH_DIRS[@]}"; do
+		[ -d "$dir" ] || continue
+		for cand in "$dir"/${MODULE}*.ko; do
+			[ -f "$cand" ] || continue
+			vm="$(modinfo -F vermagic "$cand" 2>/dev/null)"
+			msg="$msg"$'\n'"       $cand (built for ${vm%% *})"
+			any=1
+		done
+	done
+	[ "$any" = 1 ] || msg="$msg"$'\n'"       (none)"
+	die "$msg"
+fi
+[ -f "$KO" ] || die "module not found: $KO"
 
 info "module:  $KO"
 info "address: $ADDRESS"