From 5cf25de966979de2f88e24975abc25386f820741 Mon Sep 17 00:00:00 2001
From: Brad Stein <brad.stein@gmail.com>
Date: Wed, 25 Jun 2025 21:02:29 -0500
Subject: [PATCH] server logging update

---
 server/src/usb_gadget.rs | 83 ++++++++++++++++++++++++++++++++++------
 1 file changed, 71 insertions(+), 12 deletions(-)

diff --git a/server/src/usb_gadget.rs b/server/src/usb_gadget.rs
index f8ef203..cbe32ae 100644
--- a/server/src/usb_gadget.rs
+++ b/server/src/usb_gadget.rs
@@ -1,6 +1,32 @@
-use std::{fs::OpenOptions, io::Write, thread, time::Duration};
+// server/src/usb_gadget.rs
+
+use std::{fs::{self, OpenOptions}, io::Write, thread, time::Duration};
 use anyhow::{Result, Context};
-use tracing::{info, warn};
+use tracing::{debug, error, info, warn};
+
+fn wait_for_detach(udc_path: &str) {
+    for _ in 0..20 {
+        // as soon as the file is **empty**, the detach succeeded
+        if fs::read_to_string(udc_path).map(|s| s.trim().is_empty()).unwrap_or(false) {
+            debug!("🔌 UDC is now *detached*");
+            return;
+        }
+        thread::sleep(Duration::from_millis(50));
+    }
+    warn!("⏳ UDC did not detach within the expected time-out");
+}
+
+/// Like `wait_for_detach`, but the opposite condition.
+fn wait_for_attach(udc_path: &str) {
+    for _ in 0..20 {
+        if fs::read_to_string(udc_path).map(|s| !s.trim().is_empty()).unwrap_or(false) {
+            debug!("🔌 UDC is *attached* again");
+            return;
+        }
+        thread::sleep(Duration::from_millis(50));
+    }
+    warn!("⏳ UDC did not attach within the expected time-out");
+}
 
 #[derive(Clone)]
 pub struct UsbGadget {
@@ -10,15 +36,24 @@ pub struct UsbGadget {
 impl UsbGadget {
     pub fn new(name: &'static str) -> Self {
         // /sys/kernel/config/usb_gadget/<name>/UDC
-        Self { udc_file: Box::leak(
-            format!("/sys/kernel/config/usb_gadget/{name}/UDC").into_boxed_str())
+        Self {
+            udc_file: Box::leak(
+                format!("/sys/kernel/config/usb_gadget/{name}/UDC").into_boxed_str(),
+            ),
         }
     }
 
-    /// Force the host to re‑enumerate our HID gadget.
+    /// Force the host to re-enumerate our HID gadget.
+    /// Retries on EBUSY so that a transient “resource busy” never kills the whole process.
     pub fn cycle(&self) -> Result<()> {
-        info!("🔌 UDC‑cycle: detaching gadget");
-        OpenOptions::new().write(true).open(self.udc_file)?.write_all(b"")?;
+        info!("🔌 UDC-cycle: detaching gadget");
+        OpenOptions::new()
+            .write(true)
+            .open(self.udc_file)?
+            .write_all(b"")?;                // empty string → detach
+        wait_for_detach(self.udc_file);
+
+        // Let the controller settle
         thread::sleep(Duration::from_millis(200));
 
         let udc_name = std::fs::read_dir("/sys/class/udc")?
@@ -26,10 +61,34 @@ impl UsbGadget {
             .transpose()?
             .context("no UDC present")?
             .file_name();
-        info!("🔌 UDC‑cycle: re‑attaching to {}", udc_name.to_string_lossy());
-        OpenOptions::new().write(true).open(self.udc_file)?
-            .write_all(udc_name.to_str().unwrap().as_bytes())?;
-        info!("🔌 USB‑gadget cycled");
-        Ok(())
+
+        // Retry loop for the notoriously fragile re-attach
+        for attempt in 0..5 {
+            info!("🔌 UDC-cycle: re-attaching to {} (try #{attempt})", udc_name.to_string_lossy());
+            match OpenOptions::new()
+                .write(true)
+                .open(self.udc_file)?
+                .write_all(udc_name.to_str().unwrap().as_bytes())
+            {
+                Ok(()) => {
+                    wait_for_attach(self.udc_file);
+                    info!("🟢 USB-gadget cycled successfully");
+                    return Ok(());
+                }
+                Err(e) if e.raw_os_error() == Some(libc::EBUSY) => {
+                    warn!("🚧 UDC busy on re-attach – retrying in 100 ms");
+                    thread::sleep(Duration::from_millis(100));
+                    continue;
+                }
+                Err(e) => {
+                    error!("💥 unexpected error while re-attaching UDC: {e:?}");
+                    return Err(e).context("re-attaching gadget to UDC");
+                }
+            }
+        }
+
+        Err(anyhow::anyhow!(
+            "giving up after 5 attempts – UDC remained busy"
+        ))
     }
 }