basic working buildroot - rauc example

scripts/flash-cm4.sh

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+#!/bin/bash
+# flash-cm4.sh - Flash CM4 eMMC while EMMC_DISABLE jumper is bridged
+# Usage: ./scripts/flash-cm4.sh [/dev/sdX]
+#   If no device given, auto-detects the CM4 USB mass storage device.
+set -euo pipefail
+
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+BEACON_DIR="$(cd "$SCRIPT_DIR/.." && pwd)"
+REPO_ROOT="$(cd "$BEACON_DIR/.." && pwd)"
+USBBOOT_DIR="$REPO_ROOT/usbboot"
+IMAGE="$REPO_ROOT/output/images/sdcard.img.xz"
+
+# Build rpiboot from source if not already compiled
+if [ ! -x "$USBBOOT_DIR/rpiboot" ]; then
+    echo "==> Building rpiboot from source..."
+    make -C "$USBBOOT_DIR"
+fi
+
+# Step 1: Expose CM4 eMMC as USB mass storage
+echo "==> Running rpiboot to expose CM4 eMMC (EMMC_DISABLE jumper must be bridged)..."
+sudo "$USBBOOT_DIR/rpiboot" -d "$USBBOOT_DIR/mass-storage-gadget64"
+echo "==> rpiboot done, waiting for block device..."
+
+# Step 2: Find the device (explicit arg or auto-detect USB disk ~8 GiB)
+if [ -n "${1:-}" ]; then
+    DEVICE="$1"
+    echo "==> Using specified device: $DEVICE"
+else
+    DEVICE=""
+    for i in $(seq 1 30); do
+        sleep 1
+        # Detect USB block device of 7-8 GiB (CM4 eMMC)
+        DEVICE=$(lsblk -dno NAME,TRAN,SIZE \
+            | awk '$2=="usb" && ($3~/^7\.[0-9]+G$/ || $3~/^8\.[0-9]+G$/) {print "/dev/"$1}' \
+            | head -1)
+        [ -n "$DEVICE" ] && break
+        printf "  waiting... (%ds)\r" "$i"
+    done
+    if [ -z "$DEVICE" ]; then
+        echo "ERROR: CM4 eMMC did not appear as a USB block device within 30s."
+        echo "       Run 'lsblk' manually and re-run with explicit device: $0 /dev/sdX"
+        exit 1
+    fi
+    echo "==> Auto-detected CM4 eMMC at $DEVICE"
+fi
+
+# Step 3: Safety check - refuse to flash the host nvme/sata disk
+if echo "$DEVICE" | grep -qE '^/dev/(nvme|sd[a-z]{2,}|sda$)'; then
+    lsblk -dno TRAN "$DEVICE" | grep -qx usb || {
+        echo "ERROR: $DEVICE does not appear to be a USB device. Aborting."
+        exit 1
+    }
+fi
+
+# Step 4: Unmount any auto-mounted partitions
+echo "==> Unmounting $DEVICE partitions..."
+sudo umount "${DEVICE}"?* 2>/dev/null || true
+sudo umount "${DEVICE}"[0-9]* 2>/dev/null || true
+
+# Step 5: Flash via bmaptool
+echo "==> Flashing $IMAGE -> $DEVICE ..."
+sudo bmaptool copy "$IMAGE" "$DEVICE"
+sudo sync
+
+echo ""
+echo "==> Flash complete!"
+echo "    Remove the EMMC_DISABLE jumper, then power-cycle the CM4."