feat: add Interface::clear_halt(endpoint: u8) for direct endpoint halt clearing

Allows clearing a halt/stall condition by raw endpoint address without
needing to construct a typed Endpoint object. Implemented on all three
platform backends (Linux usbfs, macOS IOKit, Windows WinUSB).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/device.rs

@@ -391,6 +391,19 @@ impl Interface {
         self.backend.clone().set_alt_setting(alt_setting)
     }
 
+    /// Clear a halt / stall condition on the given endpoint and reset the
+    /// host-side data toggle.
+    ///
+    /// Use this after receiving
+    /// [`TransferError::Stall`][crate::transfer::TransferError::Stall] to clear
+    /// the error and resume use of the endpoint.
+    ///
+    /// Unlike [`Endpoint::clear_halt`], this operates directly by endpoint
+    /// address without requiring an open [`Endpoint`].
+    pub fn clear_halt(&self, endpoint: u8) -> impl MaybeFuture<Output = Result<(), Error>> {
+        self.backend.clone().clear_halt(endpoint)
+    }
+
     /// Get the current alternate setting of this interface.
     pub fn get_alt_setting(&self) -> u8 {
         self.backend.get_alt_setting()

src/platform/linux_usbfs/device.rs

@@ -757,6 +757,16 @@ impl LinuxInterface {
         })
     }
 
+    pub fn clear_halt(self: Arc<Self>, endpoint: u8) -> impl MaybeFuture<Output = Result<(), Error>> {
+        Blocking::new(move || {
+            debug!("Clear halt, endpoint {endpoint:02x}");
+            usbfs::clear_halt(&self.device.fd, endpoint).map_err(|e| match e {
+                Errno::NODEV => Error::new_os(ErrorKind::Disconnected, "device disconnected", e),
+                _ => Error::new_os(ErrorKind::Other, "failed to clear halt", e),
+            })
+        })
+    }
+
     pub fn endpoint(
         self: &Arc<Self>,
         descriptor: EndpointDescriptor,

src/platform/macos_iokit/device.rs

@@ -422,6 +422,23 @@ impl MacInterface {
         })
     }
 
+    pub fn clear_halt(self: Arc<Self>, endpoint: u8) -> impl MaybeFuture<Output = Result<(), Error>> {
+        Blocking::new(move || {
+            debug!("Clear halt, endpoint {endpoint:02x}");
+            let pipe_ref = self.interface.find_pipe_ref(endpoint).ok_or_else(|| {
+                Error::new(ErrorKind::NotFound, "endpoint not found on interface")
+            })?;
+            self.interface
+                .clear_pipe_stall_both_ends(pipe_ref)
+                .map_err(|e| match e {
+                    io_kit_sys::ret::kIOReturnNoDevice => {
+                        Error::new_os(ErrorKind::Disconnected, "device disconnected", e)
+                    }
+                    _ => Error::new_os(ErrorKind::Other, "failed to clear halt on endpoint", e),
+                })
+        })
+    }
+
     pub fn get_alt_setting(&self) -> u8 {
         self.state.lock().unwrap().alt_setting
     }

src/platform/windows_winusb/device.rs

@@ -508,6 +508,21 @@ impl WindowsInterface {
         })
     }
 
+    pub fn clear_halt(self: Arc<Self>, endpoint: u8) -> impl MaybeFuture<Output = Result<(), Error>> {
+        Blocking::new(move || {
+            debug!("Clear halt, endpoint {endpoint:02x}");
+            unsafe {
+                if WinUsb_ResetPipe(self.winusb_handle, endpoint) == TRUE {
+                    Ok(())
+                } else {
+                    Err(match GetLastError() {
+                        e => Error::new_os(ErrorKind::Other, "failed to clear halt", e),
+                    })
+                }
+            }
+        })
+    }
+
     pub fn get_alt_setting(&self) -> u8 {
         self.state.lock().unwrap().alt_setting
     }