Implement power button monitor, document device input devices

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

docs/rg35xx-plus.md

@@ -33,6 +33,19 @@ All required shared libraries are pre-installed. Most are at `/usr/lib/`, some a
 
 Shared libraries are already present — no need to bundle or build them. A native aarch64 compile (e.g. inside the arm64 Docker container) produces working binaries. Must link against glibc ≤ 2.35.
 
+## Input Devices
+
+Three input devices are registered via `/proc/bus/input/devices`:
+
+| Device | Handlers | Purpose |
+|--------|----------|---------|
+| `axp2202-pek` | `event0` | Power button (`KEY_POWER`, code 116) |
+| `ANBERNIC-keys` | `event1`, `js0` | Gamepad (d-pad, face buttons) |
+| `dierct-keys-polled` | `event2` | Shoulder buttons, menu/function keys |
+
+- **logind**: `HandlePowerKey=ignore` in `/etc/systemd/logind.conf` — systemd does not act on the power button, leaving it free for userspace handling.
+- **evtest**: Available at `/usr/bin/evtest` for debugging input events.
+
 ## Partition Layout
 
 | Device | Mount point | Filesystem | Contents |

docs/sdlamp2-fsd.md

@@ -43,6 +43,10 @@ This document specifies the functional requirements for an SDL2 based media play
 
 ## 6. Changelog
 
+### 2026-02-13 — Power button monitor in device wrapper
+
+- **Power button handling**: The `rg35xx-wrapper.sh` script now monitors `/dev/input/event0` (`axp2202-pek`) for `KEY_POWER` press events via `evtest`. On power button press, sends SIGTERM to sdlamp2 (which saves position and volume), waits 1 second, then calls `poweroff` for a clean shutdown.
+
 ### 2026-02-13 — Clean shutdown on SIGTERM/SIGINT
 
 - **Signal handling**: sdlamp2 now catches SIGTERM and SIGINT via a `sig_atomic_t` flag checked in the main loop. On signal, the existing cleanup path runs (save position, save volume, close decoder, SDL_Quit) instead of being killed instantly. This ensures position is saved when the system shuts down or the process is terminated by a wrapper script.

tools/rg35xx-wrapper.sh

@@ -4,9 +4,8 @@
 #
 # Launched by dmenu_ln instead of sdlamp2 directly. Handles device-specific
 # concerns that don't belong in the player binary:
-#   1. Start WiFi hotspot (AP mode for SSH access)
+#   1. Monitor power button and trigger clean shutdown
-#   2. Launch sdlamp2 as the foreground process
+#   2. Launch sdlamp2 as the main process
-#   3. Monitor power button and trigger clean shutdown
 #
 # Install: copy to /mnt/vendor/bin/rg35xx-wrapper.sh
 # Config:  set CMD in dmenu_ln to point here instead of sdlamp2 directly
@@ -15,49 +14,42 @@ SDLAMP2="/mnt/vendor/bin/sdlamp2"
 AUDIO_DIR="/mnt/sdcard/Music"
 
 # --- WiFi hotspot ---
-# TODO: Investigate how the stock menu starts AP mode.
+# Deprioritized: connecting the device as a WiFi client to a shared network
-# Likely candidates: hostapd, nmcli, or a vendor script in /mnt/vendor/ctrl/.
+# works fine even when sdlamp2 replaces the stock menu. Hotspot/AP mode isn't
-# Run these on the device to find out:
+# needed — SSH access works over the shared network.
-#   grep -r 'hostapd\|hotspot\|ap_mode\|wifi' /mnt/vendor/ctrl/
-#   systemctl list-units | grep -i net
-#   nmcli general status && nmcli connection show
-#
-# Placeholder — uncomment/replace once the mechanism is known:
-# nmcli connection up hotspot 2>/dev/null || true
 
 # --- Power button monitor ---
-# TODO: Investigate power button input device.
+# axp2202-pek on /dev/input/event0 sends KEY_POWER (code 116).
-# Run on device:
+# logind has HandlePowerKey=ignore, so we handle it here.
-#   cat /proc/bus/input/devices   (find the power button event device)
+POWER_EVENT_DEV="/dev/input/event0"
-#   evtest /dev/input/eventN      (confirm KEY_POWER event code)
+
-#   cat /etc/systemd/logind.conf  (check HandlePowerKey setting)
+monitor_power_button() {
-#
+  # evtest writes one line per event; filter for KEY_POWER press (value 1)
-# Strategy: read key events from the power button input device in background.
+  evtest "$POWER_EVENT_DEV" 2>/dev/null | while read -r line; do
-# When KEY_POWER (code 116) is detected, send SIGTERM to sdlamp2 and poweroff.
+    case "$line" in
-#
+      *"code 116"*"value 1"*)
-# POWER_EVENT_DEV="/dev/input/eventN"  # TBD: set after investigation
+        kill -TERM "$SDLAMP2_PID" 2>/dev/null
-#
+        sleep 1
-# monitor_power_button() {
+        poweroff
-#   # evtest writes one line per event; filter for KEY_POWER press (value 1)
+        ;;
-#   evtest "$POWER_EVENT_DEV" 2>/dev/null | while read -r line; do
+    esac
-#     case "$line" in
+  done
-#       *"code 116"*"value 1"*)
+}
-#         kill -TERM "$SDLAMP2_PID" 2>/dev/null
-#         sleep 1
-#         poweroff
-#         ;;
-#     esac
-#   done
-# }
-# monitor_power_button &
-# MONITOR_PID=$!
 
 # --- Launch sdlamp2 ---
-"$SDLAMP2" "$AUDIO_DIR"
+# Run in background so we can capture PID for the power button monitor.
+"$SDLAMP2" "$AUDIO_DIR" &
+SDLAMP2_PID=$!
+
+monitor_power_button &
+MONITOR_PID=$!
+
+# Wait for sdlamp2 to finish (signal or normal exit).
+wait "$SDLAMP2_PID"
 SDLAMP2_EXIT=$?
 
 # --- Cleanup ---
 # Kill the power button monitor if it's still running
-# kill "$MONITOR_PID" 2>/dev/null
+kill "$MONITOR_PID" 2>/dev/null
 
 exit "$SDLAMP2_EXIT"