Build Fedora aarch64 images for the Lenovo Yoga C630

Assembles a ready-to-write disk image via Gitea Actions. Mainline has carried
sdm850-lenovo-yoga-c630.dts since 5.5 and Fedora ships it in kernel-core, so
unlike aarch64-laptops/build there is no kernel or GRUB to compile — what is
left is producing an image that boots on firmware which hands Linux no device
tree.

The build runs in an aarch64 container under qemu-user and builds filesystems
from directory trees with mke2fs -d and mcopy rather than mounting loop
devices, so it works on runners that will not hand out /dev/loop-control.

A kernel-install hook writes the devicetree line into each BLS entry; without
it the first `dnf update kernel` would produce an unbootable system.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01XWRjNJMistCy6ngXH5aJLS

overlay/etc/default/grub.in

@@ -0,0 +1,13 @@
+GRUB_TIMEOUT=5
+GRUB_DISTRIBUTOR="$(sed 's, release .*$,,g' /etc/system-release)"
+GRUB_DEFAULT=saved
+GRUB_DISABLE_SUBMENU=true
+GRUB_TERMINAL_OUTPUT="console"
+GRUB_CMDLINE_LINUX="@DEVICE_CMDLINE@"
+GRUB_DISABLE_RECOVERY=true
+GRUB_ENABLE_BLSCFG=true
+
+# Consumed by grub2-mkconfig on aarch64. The BLS entries carry their own
+# `devicetree` line as well (written by 95-c630-devicetree.install), because
+# kernel-install does not read this file.
+GRUB_DEFAULT_DTB=/dtb/@DEVICE_DTB@

overlay/etc/dracut.conf.d/10-c630.conf

@@ -0,0 +1,12 @@
+# The image is built on a machine that is nothing like a C630, so the initramfs
+# must be generic — a host-only initramfs would contain the builder's drivers.
+hostonly="no"
+hostonly_cmdline="no"
+
+# UFS is the C630's only internal storage and the rootfs lives on it, so the
+# controller and PHY drivers have to be in the initramfs, not modules loaded
+# later from a filesystem we cannot yet read.
+add_drivers+=" ufshcd-core ufshcd-pltfrm ufs-qcom phy-qcom-qmp-ufs "
+
+# Needed before the display comes up, and cheap to include.
+add_drivers+=" nvmem_qfprom qcom_scm rtc-pm8xxx "

overlay/etc/kernel/install.d/95-c630-devicetree.install.in

@@ -0,0 +1,47 @@
+#!/usr/bin/bash
+#
+# Teach kernel-install about the C630's device tree.
+#
+# The C630's UEFI hands Linux no device tree, so GRUB has to load one. Fedora's
+# BLS snippets have a `devicetree` key for exactly this, but nothing in the
+# stock toolchain populates it — which means a plain `dnf update kernel` would
+# otherwise produce an unbootable entry. This hook runs after 20-grub.install
+# and patches the entry it just wrote.
+
+set -eu
+
+COMMAND="${1:?}"
+KERNEL_VERSION="${2:?}"
+
+DTB_REL="@DEVICE_DTB@"
+BOOT_ROOT="${KERNEL_INSTALL_BOOT_ROOT:-/boot}"
+ENTRIES_DIR="${BOOT_ROOT}/loader/entries"
+
+case "$COMMAND" in
+add)
+    dtb_path="/dtb-${KERNEL_VERSION}/${DTB_REL}"
+    if [ ! -e "${BOOT_ROOT}${dtb_path}" ]; then
+        echo "95-c630-devicetree: ${BOOT_ROOT}${dtb_path} is missing;" \
+             "leaving boot entries alone rather than writing a bad one" >&2
+        exit 0
+    fi
+
+    shopt -s nullglob
+    for entry in "${ENTRIES_DIR}"/*-"${KERNEL_VERSION}".conf; do
+        # Drop any stale devicetree line, then append the current one. Doing it
+        # in that order makes the hook idempotent across re-installs.
+        tmp="${entry}.c630.$$"
+        grep -v '^devicetree[[:space:]]' "$entry" > "$tmp"
+        printf 'devicetree %s\n' "$dtb_path" >> "$tmp"
+        mv -f "$tmp" "$entry"
+        echo "95-c630-devicetree: set devicetree ${dtb_path} in ${entry}"
+    done
+    ;;
+remove)
+    # The build writes its own bootstrap entry under a fixed name, which
+    # kernel-install would not otherwise clean up when the kernel goes away.
+    rm -f "${ENTRIES_DIR}/c630-${KERNEL_VERSION}.conf"
+    ;;
+esac
+
+exit 0

overlay/etc/motd.d/c630.in

@@ -0,0 +1,7 @@
+
+  Fedora @FEDORA_RELEASE@ for the @DEVICE_DESC@  (built @BUILD_DATE@ from @BUILD_REF@)
+
+  Graphics and WiFi work with the firmware Fedora ships. Audio, the sensor
+  hub and hardware video decode need per-model blobs from the Windows
+  partition — run `sudo c630-firmware` once to extract them.
+

overlay/etc/systemd/system/c630-growfs.service

@@ -0,0 +1,15 @@
+[Unit]
+Description=Grow C630 root filesystem to fill the medium
+DefaultDependencies=no
+After=systemd-remount-fs.service
+Before=local-fs.target sysinit.target
+ConditionPathExists=!/var/lib/c630/growfs-done
+
+[Service]
+Type=oneshot
+ExecStart=/usr/local/sbin/c630-growfs
+RemainAfterExit=yes
+StandardOutput=journal+console
+
+[Install]
+WantedBy=sysinit.target