Linux: improve resume handling

Author: manuelbl

java-does-usb/src/main/java/net/codecrete/usb/linux/LinuxAsyncTask.java

@@ -32,7 +32,7 @@
 import static net.codecrete.usb.linux.gen.epoll.epoll.EPOLLOUT;
 import static net.codecrete.usb.linux.gen.epoll.epoll.EPOLLWAKEUP;
 import static net.codecrete.usb.linux.gen.errno.errno.EINTR;
-import static net.codecrete.usb.linux.gen.errno.errno.ENOENT;
+import static net.codecrete.usb.linux.gen.errno.errno.ENODEV;
 import static net.codecrete.usb.linux.gen.fcntl.fcntl.FD_CLOEXEC;
 import static net.codecrete.usb.linux.gen.usbdevice_fs.usbdevice_fs.USBDEVFS_URB_TYPE_BULK;
 import static net.codecrete.usb.linux.gen.usbdevice_fs.usbdevice_fs.USBDEVFS_URB_TYPE_CONTROL;
@@ -174,8 +174,9 @@ synchronized void removeFromAsyncIOCompletion(LinuxUsbDevice device) {
             if (isMatch) {
                 var transfer = e.getValue();
                 transfer.urb = null;
-                transfer.setResultCode(ENOENT());
+                transfer.setResultCode(ENODEV());
                 transfer.setResultSize(0);
+                transfer.completion().completed(transfer);
                 availableURBs.add(urb);
             }
             return isMatch;

java-does-usb/src/main/java/net/codecrete/usb/linux/LinuxUsbDeviceRegistry.java

@@ -19,12 +19,14 @@
 import java.util.List;
 
 import static java.lang.System.Logger.Level.INFO;
+import static java.lang.foreign.MemorySegment.NULL;
 import static net.codecrete.usb.linux.EPoll.epoll_create1;
 import static net.codecrete.usb.linux.EPoll.epoll_wait;
 import static net.codecrete.usb.linux.Linux.allocateErrorState;
 import static net.codecrete.usb.linux.LinuxUsbException.throwException;
 import static net.codecrete.usb.linux.LinuxUsbException.throwLastError;
 import static net.codecrete.usb.linux.gen.epoll.epoll.EPOLLIN;
+import static net.codecrete.usb.linux.gen.errno.errno.EINTR;
 import static net.codecrete.usb.linux.gen.fcntl.fcntl.FD_CLOEXEC;
 
 /**
@@ -44,6 +46,9 @@ public class LinuxUsbDeviceRegistry extends UsbDeviceRegistry {
     private static final MemorySegment ATTR_PRODUCT;
     private static final MemorySegment ATTR_SERIAL;
 
+    private MemorySegment monitor;
+    private int monitorFd;
+
     static {
         var global = Arena.global();
 
@@ -58,13 +63,8 @@ public class LinuxUsbDeviceRegistry extends UsbDeviceRegistry {
         ATTR_SERIAL = global.allocateFrom("serial");
     }
 
-    @SuppressWarnings({"java:S1181", "java:S2189"})
-    @Override
-    protected void monitorDevices() {
-
-        int fd;
-        MemorySegment monitor;
-
+    @SuppressWarnings("java:S1181")
+    private boolean setupMonitor() {
         try {
             // setup udev monitor
             var udevInstance = udev.udev_new();
@@ -81,26 +81,34 @@ protected void monitorDevices() {
             if (udev.udev_monitor_enable_receiving(monitor) < 0)
                 throwException("internal error (udev_monitor_enable_receiving)");
 
-            fd = udev.udev_monitor_get_fd(monitor);
-            if (fd < 0)
+            monitorFd = udev.udev_monitor_get_fd(monitor);
+            if (monitorFd < 0)
                 throwException("internal error (udev_monitor_get_fd)");
 
             // create initial list of devices
             var deviceList = enumeratePresentDevices(udevInstance);
             setInitialDeviceList(deviceList);
+            return true;
 
         } catch (Throwable e) {
             enumerationFailed(e);
-            return;
+            return false;
         }
+    }
+
+    @SuppressWarnings("java:S2189")
+    @Override
+    protected void monitorDevices() {
+        if (!setupMonitor())
+            return;
 
         try (var arena = Arena.ofConfined()) {
             // create epoll
             var errorState = allocateErrorState(arena);
             var epfd = epoll_create1(FD_CLOEXEC(), errorState);
             if (epfd < 0)
                 throwLastError(errorState, "internal error (epoll_create)");
-            EPoll.addFileDescriptor(epfd, EPOLLIN(), fd);
+            EPoll.addFileDescriptor(epfd, EPOLLIN(), monitorFd);
 
             // allocate event (as output for epoll_wait)
             var event = arena.allocate(epoll_event.layout());
@@ -111,22 +119,27 @@ protected void monitorDevices() {
                 try (var cleanup = new ScopeCleanup()) {
 
                     // wait for next change
-                    epoll_wait(epfd, event, 1, -1, errorState);
+                    int res = epoll_wait(epfd, event, 1, -1, errorState);
+                    if (res < 0) {
+                        var err = Linux.getErrno(errorState);
+                        if (err == EINTR())
+                            continue; // continue on interrupt
+                        throwException(err, "internal error (epoll_wait)");
+                    }
 
                     // retrieve change
                     var udevDevice = udev.udev_monitor_receive_device(monitor);
-                    if (udevDevice == null)
-                        continue; // shouldn't happen
-
-                    cleanup.add(() -> udev.udev_device_unref(udevDevice));
+                    if (udevDevice != NULL) {
+                        cleanup.add(() -> udev.udev_device_unref(udevDevice));
 
-                    // get details
-                    var action = getDeviceAction(udevDevice);
+                        // get details
+                        var action = getDeviceAction(udevDevice);
 
-                    if ("add".equals(action)) {
-                        onDeviceConnected(udevDevice);
-                    } else if ("remove".equals(action)) {
-                        onDeviceDisconnected(udevDevice);
+                        if ("add".equals(action)) {
+                            onDeviceConnected(udevDevice);
+                        } else if ("remove".equals(action)) {
+                            onDeviceDisconnected(udevDevice);
+                        }
                     }
                 }
             }

java-does-usb/src/test/java/net/codecrete/usb/special/Continuous.java

@@ -24,7 +24,7 @@ public static void main(String[] args) throws IOException {
         new Thread(() -> readData(device)).start();
         new Thread(() -> sendData(device)).start();
 
-        System.out.println("Press Enter to exit");
+        System.out.println("Press RETURN to exit");
         System.in.read();
         device.close();
     }

test-devices/loopback-stm32/README.md

@@ -52,7 +52,7 @@ The device can be put into suspend mode by the host. It will go into a low-power
 
 A MacBook with macOS usually puts the device into suspend mode about 1 minuate after is has gone to sleep if it is not connected to a power supply. The device will wake up when the MacBook is woken up.
 
-On Windows, the device is put to sleep immediately when the Windows computer is put to sleep.
+On Windows and Linux, the device is put to sleep immediately when the computer is put to sleep or suspended.
 
 
 ## Building the firmware