server: supervise uvc helper

server/src/main.rs

@@ -7,8 +7,8 @@ use futures_util::{Stream, StreamExt};
 use gstreamer as gst;
 use std::sync::atomic::{AtomicBool, Ordering};
 use std::time::{Duration, SystemTime, UNIX_EPOCH};
-use std::{backtrace::Backtrace, panic, pin::Pin, process::Command, sync::Arc};
-use tokio::{fs::OpenOptions, io::AsyncWriteExt, sync::Mutex};
+use std::{backtrace::Backtrace, panic, pin::Pin, sync::Arc};
+use tokio::{fs::OpenOptions, io::AsyncWriteExt, process::Command, sync::Mutex};
 use tokio_stream::wrappers::ReceiverStream;
 use tonic::transport::Server;
 use tonic::{Request, Response, Status};
@@ -164,9 +164,12 @@ fn pick_uvc_device() -> anyhow::Result<String> {
     ))
 }
 
-fn spawn_uvc_control(uvc_dev: &str) -> anyhow::Result<std::process::Child> {
-    let bin = std::env::var("LESAVKA_UVC_CTRL_BIN")
-        .unwrap_or_else(|_| "/usr/local/bin/lesavka-uvc".to_string());
+fn uvc_ctrl_bin() -> String {
+    std::env::var("LESAVKA_UVC_CTRL_BIN")
+        .unwrap_or_else(|_| "/usr/local/bin/lesavka-uvc".to_string())
+}
+
+fn spawn_uvc_control(bin: &str, uvc_dev: &str) -> anyhow::Result<tokio::process::Child> {
     Command::new(bin)
         .arg("--device")
         .arg(uvc_dev)
@@ -174,6 +177,48 @@ fn spawn_uvc_control(uvc_dev: &str) -> anyhow::Result<std::process::Child> {
         .context("spawning lesavka-uvc")
 }
 
+async fn supervise_uvc_control(bin: String) {
+    let mut waiting_logged = false;
+    loop {
+        let uvc_dev = match pick_uvc_device() {
+            Ok(dev) => {
+                if waiting_logged {
+                    info!(%dev, "📷 UVC device discovered");
+                    waiting_logged = false;
+                }
+                dev
+            }
+            Err(e) => {
+                if !waiting_logged {
+                    warn!("⚠️  UVC device not ready: {e:#}");
+                    waiting_logged = true;
+                }
+                tokio::time::sleep(Duration::from_secs(2)).await;
+                continue;
+            }
+        };
+
+        match spawn_uvc_control(&bin, &uvc_dev) {
+            Ok(mut child) => {
+                info!(%uvc_dev, "📷 UVC control helper started");
+                match child.wait().await {
+                    Ok(status) => {
+                        warn!(%uvc_dev, "⚠️  lesavka-uvc exited: {status}");
+                    }
+                    Err(e) => {
+                        warn!(%uvc_dev, "⚠️  lesavka-uvc wait failed: {e:#}");
+                    }
+                }
+            }
+            Err(e) => {
+                warn!(%uvc_dev, "⚠️  failed to start lesavka-uvc: {e:#}");
+            }
+        }
+
+        tokio::time::sleep(Duration::from_secs(2)).await;
+    }
+}
+
 /*──────────────── Handler ───────────────────*/
 struct Handler {
     kb: Arc<Mutex<tokio::fs::File>>,
@@ -401,27 +446,12 @@ async fn main() -> anyhow::Result<()> {
     }));
 
     let gadget = UsbGadget::new("lesavka");
-    let _uvc_ctrl = if std::env::var("LESAVKA_DISABLE_UVC").is_err() {
-        match pick_uvc_device() {
-            Ok(uvc_dev) => match spawn_uvc_control(&uvc_dev) {
-                Ok(child) => {
-                    info!(%uvc_dev, "📷 UVC control helper started");
-                    Some(child)
-                }
-                Err(e) => {
-                    warn!("⚠️  failed to start lesavka-uvc: {e:#}");
-                    None
-                }
-            },
-            Err(e) => {
-                warn!("⚠️  UVC device not ready: {e:#}");
-                None
-            }
-        }
+    if std::env::var("LESAVKA_DISABLE_UVC").is_err() {
+        let bin = uvc_ctrl_bin();
+        tokio::spawn(supervise_uvc_control(bin));
     } else {
         info!("📷 UVC disabled (LESAVKA_DISABLE_UVC set)");
-        None
-    };
+    }
     let handler = Handler::new(gadget.clone()).await?;
 
     info!("🌐 lesavka-server listening on 0.0.0.0:50051");