Fixes to almost-ensure there is a working serial console

Why almost? Because Rpi0w uses ttyS1 instead of ttyAMA0 desipte being part of the RPi1 family...
...But it will work fine for the _second_ boot onwards, if things go according to plan.
For all other RPi models, it should work from the first boot on.

Makefile

@@ -25,6 +25,7 @@ raspi_1_buster.yaml: raspi_base_buster.yaml
 	sed "s/__LINUX_IMAGE__/linux-image-rpi/" | \
 	sed "s/__EXTRA_PKGS__/- firmware-brcm80211/" | \
 	sed "s/__DTB__/\\/usr\\/lib\\/linux-image-*-rpi\\/bcm*rpi-*.dtb/" |\
+	sed "s/__SERIAL_CONSOLE__/ttyACM0,115200/" |\
 	grep -v "__OTHER_APT_ENABLE__" |\
 	sed "s/__HOST__/rpi1/" > $@
 
@@ -33,6 +34,7 @@ raspi_2_buster.yaml: raspi_base_buster.yaml
 	sed "s/__LINUX_IMAGE__/linux-image-armmp/" | \
 	grep -v "__EXTRA_PKGS__" | \
 	sed "s/__DTB__/\\/usr\\/lib\\/linux-image-*-armmp\\/bcm*rpi*.dtb/" |\
+	sed "s/__SERIAL_CONSOLE__/ttyACM0,115200/" |\
 	sed "s/__OTHER_APT_ENABLE__//" |\
 	sed "s/__HOST__/rpi2/" > $@
 
@@ -41,6 +43,7 @@ raspi_3_buster.yaml: raspi_base_buster.yaml
 	sed "s/__LINUX_IMAGE__/linux-image-arm64/" | \
 	sed "s/__EXTRA_PKGS__/- firmware-brcm80211/" | \
 	sed "s/__DTB__/\\/usr\\/lib\\/linux-image-*-arm64\\/broadcom\\/bcm*rpi*.dtb/" |\
+	sed "s/__SERIAL_CONSOLE__/ttyS1,115200/" |\
 	sed "s/__OTHER_APT_ENABLE__//" |\
 	sed "s/__HOST__/rpi3/" > $@
 
@@ -52,6 +55,7 @@ raspi_4_buster.yaml: raspi_base_buster.yaml
 	sed "s/__LINUX_IMAGE__/linux-image-arm64\/buster-backports/" | \
 	sed "s/__EXTRA_PKGS__/- firmware-brcm80211\/buster-backports/" | \
 	sed "s/__DTB__/\\/usr\\/lib\\/linux-image-*-arm64\\/broadcom\\/bcm*rpi*.dtb/" |\
+	sed "s/__SERIAL_CONSOLE__/ttyS1,115200/" |\
 	sed "s/__OTHER_APT_ENABLE__/deb http:\/\/deb.debian.org\/debian\/ buster-backports main contrib non-free # raspi 4 needs a kernel and raspi-firmware newer than buster's/" |\
 	sed "s/__HOST__/rpi4/" > $@
 
@@ -67,6 +71,7 @@ raspi_1_bullseye.yaml: raspi_base_bullseye.yaml
 	sed "s/__LINUX_IMAGE__/linux-image-rpi/" | \
 	sed "s/__EXTRA_PKGS__/- firmware-brcm80211/" | \
 	sed "s/__DTB__/\\/usr\\/lib\\/linux-image-*-rpi\\/bcm*rpi-*.dtb/" |\
+	sed "s/__SERIAL_CONSOLE__/ttyACM0,115200/" |\
 	sed "s/__HOST__/rpi_1/" > $@
 
 raspi_2_bullseye.yaml: raspi_base_bullseye.yaml
@@ -74,6 +79,7 @@ raspi_2_bullseye.yaml: raspi_base_bullseye.yaml
 	sed "s/__LINUX_IMAGE__/linux-image-armmp/" | \
 	grep -v "__EXTRA_PKGS__" | \
 	sed "s/__DTB__/\\/usr\\/lib\\/linux-image-*-armmp\\/bcm*rpi*.dtb/" |\
+	sed "s/__SERIAL_CONSOLE__/ttyACM0,115200/" |\
 	sed "s/__HOST__/rpi_2/" > $@
 
 raspi_3_bullseye.yaml: raspi_base_bullseye.yaml
@@ -81,6 +87,7 @@ raspi_3_bullseye.yaml: raspi_base_bullseye.yaml
 	sed "s/__LINUX_IMAGE__/linux-image-arm64/" | \
 	sed "s/__EXTRA_PKGS__/- firmware-brcm80211/" | \
 	sed "s/__DTB__/\\/usr\\/lib\\/linux-image-*-arm64\\/broadcom\\/bcm*rpi*.dtb/" |\
+	sed "s/__SERIAL_CONSOLE__/ttyS1,115200/" |\
 	sed "s/__HOST__/rpi_3/" > $@
 
 raspi_4_bullseye.yaml: raspi_base_bullseye.yaml
@@ -89,6 +96,7 @@ raspi_4_bullseye.yaml: raspi_base_bullseye.yaml
 	sed "s/__LINUX_IMAGE__/linux-image-arm64/" | \
 	sed "s/__EXTRA_PKGS__/- firmware-brcm80211/" | \
 	sed "s/__DTB__/\\/usr\\/lib\\/linux-image-*-arm64\\/broadcom\\/bcm*rpi*.dtb/" |\
+	sed "s/__SERIAL_CONSOLE__/ttyS1,115200/" |\
 	sed "s/__HOST__/rpi_4/" > $@
 
 %.sha256: %.img.xz

raspi_master.yaml

@@ -102,8 +102,11 @@ steps:
       mkdir -p "${ROOT?}/etc/systemd/system/systemd-remount-fs.service.requires/"
       ln -s /etc/systemd/system/rpi-resizerootfs.service "${ROOT?}/etc/systemd/system/systemd-remount-fs.service.requires/rpi-resizerootfs.service"
 
-      install -m 644 -o root -g root rootfs/etc/systemd/system/rpi-generate-ssh-host-keys.service "${ROOT?}/etc/systemd/system/"
+      install -m 644 -o root -g root rootfs/etc/systemd/system/rpi-reconfigure-raspi-firmware.service "${ROOT?}/etc/systemd/system/"
       mkdir -p "${ROOT?}/etc/systemd/system/multi-user.target.requires/"
+      ln -s /etc/systemd/system/rpi-reconfigure-raspi-firmware.service "${ROOT?}/etc/systemd/system/multi-user.target.requires/rpi-reconfigure-raspi-firmware.service"
+
+      install -m 644 -o root -g root rootfs/etc/systemd/system/rpi-generate-ssh-host-keys.service "${ROOT?}/etc/systemd/system/"
       ln -s /etc/systemd/system/rpi-generate-ssh-host-keys.service "${ROOT?}/etc/systemd/system/multi-user.target.requires/rpi-generate-ssh-host-keys.service"
       rm -f "${ROOT?}"/etc/ssh/ssh_host_*_key*
     root-fs: /
@@ -122,9 +125,12 @@ steps:
 
   # Modify the kernel commandline we take from the firmware to boot from
   # the partition labeled raspiroot instead of forcing it to mmcblk0p2
+  #
+  # These changes will be overwritten after the hardware is probed
+  # after dpkg reconfigures raspi-firmware (upon first boot).
   - chroot: /
     shell: |
-      ls -aR /boot
+      sed -i 's/^/console=__SERIAL_CONSOLE__ /' /boot/firmware/cmdline.txt
       sed -i 's/.dev.mmcblk0p2/LABEL=RASPIROOT/' /boot/firmware/cmdline.txt
 
   # TODO(https://github.com/larswirzenius/vmdb2/issues/24): remove once vmdb

rootfs/etc/systemd/system/rpi-reconfigure-raspi-firmware.service

@@ -0,0 +1,14 @@
+[Unit]
+Description=Reconfigure raspi-firmware to regenerate config.txt matching actual hardware
+Before=local-fs-pre.target
+DefaultDependencies=no
+RequiresMountsFor=/boot/firmware
+
+[Service]
+Type=oneshot
+TimeoutSec=infinity
+ExecStart=/usr/sbin/dpkg-reconfigure raspi-firmware
+ExecStart=/bin/systemctl --no-reload disable %n
+
+[Install]
+RequiredBy=local-fs-pre.target