diff --git a/.github/workflows/docker-images/yocto-builder/entrypoint-yocto-check-layer.sh b/.github/workflows/docker-images/yocto-builder/entrypoint-yocto-check-layer.sh
index 5cf3736..55566a9 100755
--- a/.github/workflows/docker-images/yocto-builder/entrypoint-yocto-check-layer.sh
+++ b/.github/workflows/docker-images/yocto-builder/entrypoint-yocto-check-layer.sh
@@ -30,5 +30,18 @@ done
 
 # shellcheck disable=SC1091,SC2240
 . ./openembedded-core/oe-init-build-env build
+
+# Build configuration
+printf "\n# ------ ci ------\n" >> conf/local.conf
+cat <<EOCONF >>conf/local.conf
+LICENSE_FLAGS_ACCEPTED = "synaptics-killswitch"
+EOCONF
+
+MACHINES="$(find "$GIT_REPO_PATH/conf/machine" -maxdepth 1 -name '*.conf' \
+    -exec basename {} .conf \; | sort)"
+[ -n "$MACHINES" ] ||
+    error "No machines found under $GIT_REPO_PATH/conf/machine ."
+
+# shellcheck disable=SC2086
 yocto-check-layer --with-software-layer-signature-check --debug \
-    "$GIT_REPO_PATH"
+    "$GIT_REPO_PATH" --machines $MACHINES
diff --git a/.github/workflows/yocto-builds.yml b/.github/workflows/yocto-builds.yml
index b16cb09..997af5c 100644
--- a/.github/workflows/yocto-builds.yml
+++ b/.github/workflows/yocto-builds.yml
@@ -14,23 +14,15 @@ jobs:
     strategy:
       fail-fast: true
       matrix:
+        # Tier 1: one machine per tune / kernel defconfig. All machines are
+        # signature checked by yocto-check-layer in yocto-layer.yml.
         machine:
-          - raspberrypi
-          - raspberrypi0-2w-64
-          - raspberrypi0-2w
-          - raspberrypi0
           - raspberrypi0-wifi
-          - raspberrypi2-64
-          - raspberrypi2
-          - raspberrypi3-64
-          - raspberrypi3
-          - raspberrypi4-64
-          - raspberrypi4
-          - raspberrypi5
-          - raspberrypi-cm3
-          - raspberrypi-cm
           - raspberrypi-armv7
           - raspberrypi-armv8
+          - raspberrypi3-64
+          - raspberrypi4-64
+          - raspberrypi5
         image: [rpi-test-image]
         distro: [poky]
     runs-on: [self-hosted, Linux]
diff --git a/.github/workflows/yocto-layer.yml b/.github/workflows/yocto-layer.yml
index 555241b..69ee81c 100644
--- a/.github/workflows/yocto-layer.yml
+++ b/.github/workflows/yocto-layer.yml
@@ -27,6 +27,7 @@ jobs:
             .github/workflows/docker-images/yocto-builder/**
             .github/workflows/docker-images/*.sh
             .github/workflows/yocto-builds.yml
+            .github/workflows/yocto-layer.yml
             classes/**
             conf/**
             dynamic-layers/**