usb-host: handle USBDEVFS_SETCONFIGURATION returning EBUSY

In case the host uses the usb device usbfs will refuse to set the
configuration due to the device being busy.  Handle this case by
disconnection the interfaces, then trying again.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

usb-linux.c

@@ -485,6 +485,26 @@ static int usb_host_disconnect_ifaces(USBHostDevice *dev, int nb_interfaces)
     return 0;
 }
 
+static int usb_linux_get_num_interfaces(USBHostDevice *s)
+{
+    char device_name[64], line[1024];
+    int num_interfaces = 0;
+
+    if (usb_fs_type != USB_FS_SYS) {
+        return -1;
+    }
+
+    sprintf(device_name, "%d-%s", s->bus_num, s->port);
+    if (!usb_host_read_file(line, sizeof(line), "bNumInterfaces",
+                            device_name)) {
+        return -1;
+    }
+    if (sscanf(line, "%d", &num_interfaces) != 1) {
+        return -1;
+    }
+    return num_interfaces;
+}
+
 static int usb_host_claim_interfaces(USBHostDevice *dev, int configuration)
 {
     const char *op = NULL;
@@ -901,14 +921,28 @@ static int usb_host_set_address(USBHostDevice *s, int addr)
 
 static int usb_host_set_config(USBHostDevice *s, int config)
 {
+    int ret, first = 1;
+
     trace_usb_host_set_config(s->bus_num, s->addr, config);
 
     usb_host_release_interfaces(s);
 
-    int ret = ioctl(s->fd, USBDEVFS_SETCONFIGURATION, &config);
+again:
+    ret = ioctl(s->fd, USBDEVFS_SETCONFIGURATION, &config);
 
     DPRINTF("husb: ctrl set config %d ret %d errno %d\n", config, ret, errno);
 
+    if (ret < 0 && errno == EBUSY && first) {
+        /* happens if usb device is in use by host drivers */
+        int count = usb_linux_get_num_interfaces(s);
+        if (count > 0) {
+            DPRINTF("husb: busy -> disconnecting %d interfaces\n", count);
+            usb_host_disconnect_ifaces(s, count);
+            first = 0;
+            goto again;
+        }
+    }
+
     if (ret < 0) {
         return ctrl_error();
     }