From 8559b460b1caf1b619ef25ef9bb251cfa8282db9 Mon Sep 17 00:00:00 2001
From: Krzysztof Nazarewski <gpg@kdn.im>
Date: Thu, 18 Apr 2024 13:33:19 +0200
Subject: [PATCH] edido: init

---
 pkgs/by-name/ed/edido/edido.sh    | 176 ++++++++++++++++++++++++++++++
 pkgs/by-name/ed/edido/package.nix |  19 ++++
 2 files changed, 195 insertions(+)
 create mode 100755 pkgs/by-name/ed/edido/edido.sh
 create mode 100644 pkgs/by-name/ed/edido/package.nix

diff --git a/pkgs/by-name/ed/edido/edido.sh b/pkgs/by-name/ed/edido/edido.sh
new file mode 100755
index 000000000000..136205386ee1
--- /dev/null
+++ b/pkgs/by-name/ed/edido/edido.sh
@@ -0,0 +1,176 @@
+#!/usr/bin/env bash
+set -eEuo pipefail
+test -z "${DEBUG:-}" || set -x
+set -eEuo pipefail
+
+FIRMWARE_PATH="${EDID_PATH:-"/run/current-system/firmware"}"
+mapfile -t edid_paths <<<"${FIRMWARE_PATH//":"/$'\n'}"
+
+err() {
+  LOGGER="ERROR" log "$@"
+  return 1
+}
+
+log() {
+  # shellcheck disable=SC2059
+  printf "[${LOGGER:-"INFO"}] $1\n" "${@:2}" >&2
+}
+
+find_path() {
+  local filePath="$1"
+  mapfile -t candidates < <(
+    set -x
+    find -L "${@:2}" -path "*/${filePath}"
+  )
+  if test "${#candidates[@]}" -eq 0; then
+    log "'%s' path not found" "${filePath}"
+    return 1
+  fi
+  log "'%s' path found at %s" "${filePath}" "${candidates[0]}"
+  echo -n "${candidates[0]}"
+}
+
+wait_for_file() {
+  local filePath="$1"
+  until find_path "${filePath}" "${@:2}"; do
+    backoff "${filePath}"
+  done
+}
+
+backoff() {
+  local what="$1" sleepFor
+
+  backoff_start="${backoff_start:-"5"}"
+  backoff_current="${backoff_current:-"${backoff_start}"}"
+  backoff_jitter_multiplier="${backoff_jitter_multiplier:-"0.3"}"
+  backoff_multiplier="${backoff_multiplier:-1.5}"
+
+  sleepFor="$(bc <<<"${backoff_current} + ${RANDOM} % (${backoff_current} * ${backoff_jitter_multiplier})")"
+
+  log "still waiting for '%s', retry in %s sec..." "${what}" "${sleepFor}"
+  sleep "${sleepFor}"
+  backoff_current="$(bc <<<"scale=2; ${backoff_current} * ${backoff_multiplier}")"
+
+}
+
+force_mode() {
+  local connPath="$1" newMode="$2" currentMode
+  currentMode="$(cat "$connPath/force")"
+  if test "${currentMode}" == "${newMode}"; then
+    log "video mode is already '%s'" "${currentMode}"
+    return
+  fi
+  log "changing video mode from '%s' to '%s'" "${currentMode}" "${newMode}"
+  echo "${newMode}" >"$connPath/force"
+  CHANGED=1
+}
+
+force_edid() {
+  local connPath="$1" edidPath="$2"
+}
+
+apply_mode() {
+  local connPath="$1" mode="$2"
+  test -n "$mode" || return
+  log "setting up fb mode..."
+
+  # see https://github.com/torvalds/linux/blob/8cd26fd90c1ad7acdcfb9f69ca99d13aa7b24561/drivers/gpu/drm/drm_sysfs.c#L202-L207
+  # see https://docs.kernel.org/fb/modedb.html
+  case "${mode}" in
+  *d) force_mode "$connPath" off ;;
+  *e) force_mode "$connPath" on ;;
+  *D) force_mode "$connPath" on-digital ;;
+  esac
+}
+
+apply_edid() {
+  local connPath="$1" edidFilename="$2" edidPath
+  test -n "${edidFilename}" || return
+  log "loading EDID override..."
+  edidPath="$(find_path "${edidFilename}" "${edid_paths[@]/%/"/"}" -maxdepth 2)"
+
+  force_edid "${connPath}" "$edidPath"
+  cat "$edidPath" >"${connPath}/edid_override"
+
+  if cmp "${connPath}/edid_override" "${edidPath}" &>/dev/null; then
+    log "EDID is already up to date with '%s'" "${edidPath}"
+  else
+    log "applying EDID override from ${edidPath}"
+    cat "$edidPath" >"${connPath}/edid_override"
+    CHANGED=1
+  fi
+}
+
+load() {
+  local conn="$1" edidFilename="$2" mode="$3"
+  export LOGGER="$conn:${edidFilename}:$mode"
+  CHANGED="${CHANGED:-0}"
+
+  log "starting configuration"
+  local connPath
+  connPath="$(wait_for_file "$conn" /sys/kernel/debug/dri/ -maxdepth 2 -type d)"
+  apply_edid "${connPath}" "${edidFilename}"
+  apply_mode "${connPath}" "$mode"
+
+  if test "${CHANGED}" != 0; then
+    log "changes detected, triggering hotplug"
+    echo 1 >"${connPath}/trigger_hotplug"
+  else
+    log "no changes detected, skipping hotplug trigger"
+  fi
+}
+
+main() {
+  if [[ $EUID -ne 0 ]]; then
+    err "must be run as root"
+  fi
+
+  if test "$#" == 0; then
+    log "loading kernel parameters from /proc/cmdline"
+    # replace script arguments with kernel parameters
+    mapfile -t args < <(xargs -n1 </proc/cmdline)
+  else
+    log "loading kernel parameters compatible arguments from commandline"
+    args=("$@")
+  fi
+
+  local -A edids modes connectors
+  local -a entries
+  local key value
+
+  for arg in "${args[@]}"; do
+    key="${arg%%=*}"
+    value=""
+    test "${key}" == "${arg}" || value="${arg#*=}"
+
+    case "${key}" in
+    video)
+      # one argument per connector:
+      #   video=DP-4:e video=DP-1:e
+      connector="${value%:*}"
+      mode="${value#*:}"
+      connectors["${connector}"]=""
+      modes["$connector"]="$mode"
+      ;;
+    drm.edid_firmware)
+      # single argument for all connectors:
+      #   drm.edid_firmware=DP-4:edid/one.bin,DP-1:edid/two.bin
+      mapfile -t entries <<<"${value//","/$'\n'}"
+      for entry in "${entries[@]}"; do
+        connector="${entry%:*}"
+        edidFilename="${entry#*:}"
+        connectors["${connector}"]=""
+        edids["${connector}"]="${edidFilename}"
+      done
+      ;;
+    esac
+  done
+
+  for connector in "${!connectors[@]}"; do
+    # spawn in a subshell to easily adjust and runtime modify global variables
+    (load "${connector}" "${edids["${connector}"]:-""}" "${modes["${connector}"]:-""}") &
+  done
+  wait
+}
+
+main "$@"
diff --git a/pkgs/by-name/ed/edido/package.nix b/pkgs/by-name/ed/edido/package.nix
new file mode 100644
index 000000000000..2d1f69e6a740
--- /dev/null
+++ b/pkgs/by-name/ed/edido/package.nix
@@ -0,0 +1,19 @@
+{ lib
+, writeShellApplication
+, bc
+, diffutils
+, findutils
+, coreutils
+, firmwarePaths ? [
+    "/run/current-system/firmware"
+  ]
+}:
+writeShellApplication {
+  name = "edido";
+  meta.description = "A tool to apply display configuration from `boot.kernelParams`.";
+  runtimeInputs = [ diffutils findutils coreutils bc ];
+  text = ''
+    FIRMWARE_PATH="''${FIRMWARE_PATH:-"${builtins.concatStringsSep ":" firmwarePaths}"}"
+    ${builtins.readFile ./edido.sh}
+  '';
+}