Make the kiosk autologin survive a reboot, and allow forcing a display mode

Two problems on musicdolphin, found after its first reboot.

getty@tty1 was never enabled. The role installed the autologin drop-in and the
handler restarted the unit, which works until the next boot - these images do
not enable getty@tty1 themselves, getty.target pulls in getty-static.service and
nothing else, so after a reboot nobody logs in and the kiosk never starts. Enable
it as well as starting it.

And the attached screen reads back 0 bytes of EDID on both micro-HDMI ports while
reporting "disconnected", so the kernel offers no modes, no framebuffer is
created, and X exits with "no screens found". That is the signature of a cable or
adapter whose DDC/HPD lines are broken but whose video pairs are fine. Forcing
the connector on is not enough on its own - with no EDID there is still no mode
to set - so allow a `video=` kernel parameter, which forces the output and names
the mode. hdmi_force_hotplug=1 is no use here; vc4-kms-v3d ignores it.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

host_vars/musicdolphin.yml

@@ -16,3 +16,8 @@ mediapi_has_dhtsensor: true
 mediapi_install_kidsmusic: true
 mediapi_has_monitor: true
 musicmouse_version: deploy/musicdolphin
+
+# The attached screen reads back 0 bytes of EDID on both micro-HDMI ports and reports
+# "disconnected", so the kernel offers no modes and X dies with "no screens found".
+# Force the mode instead. Use the port nearest the USB-C jack (HDMI0 = HDMI-A-1).
+pi_kiosk_force_mode: "HDMI-A-1:1920x1080@60e"

roles/pi_kiosk/defaults/main.yml

@@ -1,3 +1,14 @@
 ---
 pi_kiosk_user: "kiosk"
 pi_kiosk_url: "http://localhost:8080"
+
+# Force a mode on the kiosk output, as a `video=` kernel parameter, e.g.
+# "HDMI-A-1:1920x1080@60e" (the trailing `e` forces the output enabled). Empty means
+# "let EDID decide", which is what you want whenever EDID can be read.
+#
+# This is for a display the Pi cannot see: a micro-HDMI cable or adapter whose DDC/HPD
+# lines are broken but whose video pairs are fine reads back 0 bytes of EDID and
+# reports "disconnected", while displaying perfectly once a mode is forced. Note
+# hdmi_force_hotplug=1 does nothing here - it is ignored by the vc4-kms-v3d driver
+# these images use.
+pi_kiosk_force_mode: ""

roles/pi_kiosk/handlers/main.yml

@@ -4,3 +4,9 @@
     name: "getty@tty1"
     state: restarted
     daemon_reload: "yes"
+
+- name: Warn that a reboot is needed
+  ansible.builtin.debug:
+    msg: >-
+      /boot/firmware/cmdline.txt changed - the forced display mode only takes effect
+      after a reboot.

roles/pi_kiosk/tasks/main.yml

@@ -29,6 +29,17 @@
     mode: "0644"
   notify: Reload systemd and restart getty
 
+- name: Enable the autologin getty on tty1
+  # Enabling it is the part that survives a reboot. These images do not enable
+  # getty@tty1 themselves - getty.target pulls in getty-static.service and nothing
+  # else - so without this the drop-in above is installed, the handler starts the unit
+  # once, and the kiosk then silently stops coming up after the next reboot.
+  ansible.builtin.systemd:
+    name: "getty@tty1"
+    enabled: true
+    state: started
+    daemon_reload: true
+
 - name: Install .bash_profile (starts X on tty1 login)
   ansible.builtin.template:
     src: bash_profile.j2
@@ -57,3 +68,23 @@
     src: policies.json
     dest: /etc/firefox-esr/policies.json
     mode: "0644"
+
+- name: Read the current kernel command line
+  ansible.builtin.slurp:
+    src: /boot/firmware/cmdline.txt
+  register: pi_kiosk_cmdline
+  when: pi_kiosk_force_mode | length > 0
+
+- name: Force a mode on the kiosk output
+  # cmdline.txt is a single line of space-separated parameters. Rebuild it by dropping
+  # any video= we set before and appending the current one, so changing the mode
+  # replaces it rather than stacking a second one.
+  ansible.builtin.copy:
+    dest: /boot/firmware/cmdline.txt
+    content: >-
+      {{ ((pi_kiosk_cmdline.content | b64decode).split()
+          | reject('match', '^video=') | list
+          + ['video=' ~ pi_kiosk_force_mode]) | join(' ') }}
+    mode: "0755"
+  when: pi_kiosk_force_mode | length > 0
+  notify: Warn that a reboot is needed