From 4419b5ce7386569c848d4e0cb73c8f258e108e0a Mon Sep 17 00:00:00 2001
From: Brad Stein <brad.stein@gmail.com>
Date: Thu, 26 Jun 2025 01:11:14 -0500
Subject: [PATCH] server udc fix

---
 server/src/usb_gadget.rs | 24 +++++++++++++++++++++---
 1 file changed, 21 insertions(+), 3 deletions(-)

diff --git a/server/src/usb_gadget.rs b/server/src/usb_gadget.rs
index 4030444..c11890f 100644
--- a/server/src/usb_gadget.rs
+++ b/server/src/usb_gadget.rs
@@ -85,7 +85,26 @@ impl UsbGadget {
 
         /* 1 – detach gadget */
         info!("🔌 detaching gadget from {ctrl}");
-        Self::write_attr(self.udc_file, "none")?;
+        // a) drop pull‑ups (if the controller offers the switch)
+        let sc = format!("/sys/class/udc/{ctrl}/soft_connect");
+        let _ = Self::write_attr(&sc, "0");          // ignore errors – not all HW has it
+
+        // b) clear the UDC attribute; the kernel may transiently answer EBUSY
+        for attempt in 1..=10 {
+            match Self::write_attr(self.udc_file, "") {
+                Ok(_) => break,
+                Err(err) if {
+                    // only swallow EBUSY
+                    err.downcast_ref::<std::io::Error>()
+                       .and_then(|io| io.raw_os_error())
+                       == Some(libc::EBUSY) && attempt < 10
+                } => {
+                    trace!("⏳ UDC busy (attempt {attempt}/10) – retrying…");
+                    thread::sleep(Duration::from_millis(100));
+                }
+                Err(err) => return Err(err),
+            }
+        }
         Self::wait_state(&ctrl, "not attached", 3_000)?;
 
         /* 2 – reset driver */
@@ -97,7 +116,6 @@ impl UsbGadget {
         /* 4 – re‑attach + pull‑up */
         info!("🔌 re‑attaching gadget to {ctrl}");
         Self::write_attr(self.udc_file, &ctrl)?;
-        let sc = format!("/sys/class/udc/{ctrl}/soft_connect");
         if Path::new(&sc).exists() {
             // try to set the pull-up; ignore if the kernel rejects it
             match Self::write_attr(&sc, "1") {
@@ -107,7 +125,7 @@ impl UsbGadget {
                         match io.raw_os_error() {
                             // EINVAL | EPERM | ENOENT
                             Some(libc::EINVAL) | Some(libc::EPERM) | Some(libc::ENOENT) => {
-                                warn!("soft_connect unsupported ({io}); continuing");
+                                warn!("⚠️ soft_connect unsupported ({io}); continuing");
                             }
                             _ => return Err(err),        // propagate all other errors
                         }