Add VFL_DIR_M2M to v4l2-loopback-dc

This allows other programs (eg. ffmpeg) to use the v4l2_dc device

Author: aramg

v4l2loopback/v4l2loopback-dc.c

@@ -2149,6 +2149,14 @@ init_vdev           (struct video_device *vdev)
     V4L2_CAP_VIDEO_CAPTURE |
     V4L2_CAP_STREAMING | V4L2_CAP_READWRITE;
   #endif
+
+  /* since kernel-3.7, there is a new field 'vfl_dir' that has to be
+   * set to VFL_DIR_M2M for bidrectional devices.
+   * For DroidCam, this allows other programs like ffmpeg to write to
+   * the device.  */
+  #ifdef VFL_DIR_M2M
+    vdev->vfl_dir = VFL_DIR_M2M;
+  #endif
 #if DEBUG
 #if LINUX_VERSION_CODE < KERNEL_VERSION(3, 20, 0)
    vdev->debug = V4L2_DEBUG_IOCTL | V4L2_DEBUG_IOCTL_ARG;