Add script for checking the HDMI status (#1924)

Resolves tiny-pilot/tinypilot-pro#1635.

This PR adds a privileged script for checking the status of the HDMI
capture chip. The check status is also included in the debug logs.

<img width="1022" height="506" alt="Screenshot 2025-10-16 at 21 54 42"
src="https://github.com/user-attachments/assets/3e24a6d0-7421-425d-9abc-b039fd770363"
/>

<img width="826" height="905" alt="Screenshot 2025-10-16 at 21 35 51"
src="https://github.com/user-attachments/assets/66471a78-13a1-42db-af46-aeb0a78df50d"
/>
<a data-ca-tag
href="https://codeapprove.com/pr/tiny-pilot/tinypilot/1924"><img
src="https://codeapprove.com/external/github-tag-allbg.png" alt="Review
on CodeApprove" /></a>

---------

Co-authored-by: Jan Heuermann <[email protected]>

Author: jotaen4tinypilot

debian-pkg/etc/sudoers.d/tinypilot

@@ -1,4 +1,5 @@
 tinypilot ALL=(ALL) NOPASSWD: /opt/tinypilot-privileged/scripts/change-hostname
+tinypilot ALL=(ALL) NOPASSWD: /opt/tinypilot-privileged/scripts/check-hdmi-status
 tinypilot ALL=(ALL) NOPASSWD: /opt/tinypilot-privileged/scripts/collect-debug-logs
 tinypilot ALL=(ALL) NOPASSWD: /opt/tinypilot-privileged/scripts/configure-janus
 tinypilot ALL=(ALL) NOPASSWD: /opt/tinypilot-privileged/scripts/disable-wifi

debian-pkg/opt/tinypilot-privileged/scripts/check-hdmi-status

@@ -0,0 +1,132 @@
+#!/bin/bash
+#
+# This script checks the status of the HDMI capture chip.
+# It reports the status as output on stdout (either as 'true' or 'false').
+#
+# Note: the script only supports checking tc358743 capture chips, whose input
+# is mapped to /dev/video0. This applies to e.g. Voyager 2a hardware products,
+# but not necessarily to Community/Hobbyist configurations.
+
+# Exit on unset variable.
+set -u
+
+# Exit on first error.
+set -e
+
+if (( "${EUID}" != 0 )); then
+  >&2 echo 'This script requires root privileges.'
+  >&2 echo 'Please re-run with sudo:'
+  >&2 echo "  sudo $0 $*"
+  >&2 exit 1
+fi
+
+print_help() {
+  cat << EOF
+Usage: ${0##*/} [--help | --power | --signal]
+
+Options:
+  --help      Display this help and exit.
+  --power     Check whether a powered HDMI cable is connected to the capture
+              chip. Note: this may not produce accurate results on Voyager 2a
+              hardware (or earlier).
+  --signal    Check whether the capture chip receives signal.
+              (This implies that a powered HDMI cable is connected.)
+EOF
+}
+
+readonly VIDEO_DEVICE='/dev/video0'
+
+# Check hardware preconditions.
+if ! [[ -e "${VIDEO_DEVICE}" ]]; then
+  >&2 echo "Error: no video input device mapped to '${VIDEO_DEVICE}'."
+  exit 1
+fi
+
+if ! grep -q 'dtoverlay=tc358743' /boot/config.txt; then
+  >&2 echo 'Error: no tc358743 capture chip found.'
+  exit 1
+fi
+
+# Parse command-line arguments.
+if [[ $# -eq 0 ]]; then
+  print_help
+  exit 1
+fi
+
+while (( "$#" > 0 )); do
+  case "$1" in
+    --help)
+      print_help
+      exit
+      ;;
+    --power)
+      if [[ -n "${ACTION:-}" ]]; then
+         >&2 echo 'Error: please only specify one flag.'
+         exit 1
+      fi
+      ACTION='power'
+      shift
+      ;;
+    --signal)
+      if [[ -n "${ACTION:-}" ]]; then
+         >&2 echo 'Error: please only specify one flag.'
+         exit 1
+      fi
+      ACTION='signal'
+      shift
+      ;;
+    *)
+      >&2 echo "Unknown option: $1"
+      print_help >&2
+      exit 1
+      ;;
+  esac
+done
+
+# Validate that ACTION is set.
+if [[ -z "${ACTION:-}" ]]; then
+  >&2 echo 'Error: please specify a valid flag.'
+  print_help >&2
+  exit 1
+fi
+readonly ACTION
+
+# Check for power.
+if [[ "${ACTION:-}" == 'power' ]]; then
+  # The output of the '--get-ctrl power_present' command is either
+  # 'power_present: 0' or 'power_present: 1'.
+  # Note that on devices prior to Voyager 3, the behavior of this command may
+  # be unexpected, as it can persistently report 'power_present: 1', even if
+  # no powered HDMI cable is connected (anymore).
+  OUTPUT="$(v4l2-ctl --device "${VIDEO_DEVICE}" --get-ctrl power_present)"
+  readonly OUTPUT
+  if [[ "${OUTPUT}" == 'power_present: 1' ]]; then
+    echo 'true'
+  else
+    echo 'false'
+  fi
+
+# Check whether there is an active signal.
+elif [[ "${ACTION:-}" == 'signal' ]]; then
+  # If there is signal, the output of '--get-input' will look like so:
+  #
+  #    Video input : 0 (Camera 0: ok)
+  #
+  # Otherwise, the output will look like so:
+  #
+  #    Video input : 0 (Camera 0: no signal, no sync lock)
+  #
+  # For reference, the output is assembled here:
+  # https://git.linuxtv.org/v4l-utils.git/tree/utils/v4l2-ctl/v4l2-ctl-io.cpp#n122
+  OUTPUT="$(v4l2-ctl --device "${VIDEO_DEVICE}" --get-input)"
+  readonly OUTPUT
+  if [[ "${OUTPUT}" == *'(Camera 0: ok)'* ]]; then
+    echo 'true'
+  else
+    echo 'false'
+  fi
+
+else
+  print_help
+  exit 1
+fi

debian-pkg/opt/tinypilot-privileged/scripts/collect-debug-logs

@@ -192,6 +192,16 @@ print_info "Checking TinyPilot streaming mode..."
   printf "\n\n"
 } >> "${LOG_FILE}"
 
+print_info "Checking status of HDMI capture chip..."
+{
+  echo "HDMI capture chip status"
+  HAS_POWER="$(/opt/tinypilot-privileged/scripts/check-hdmi-status --power)"
+  HAS_SIGNAL="$(/opt/tinypilot-privileged/scripts/check-hdmi-status --signal)"
+  echo "Power: ${HAS_POWER:-n/a}"
+  echo "Signal: ${HAS_SIGNAL:-n/a}"
+  printf "\n"
+} >> "${LOG_FILE}"
+
 print_info "Checking TinyPilot settings..."
 {
   printf "TinyPilot settings.yml\n"