Fix device capability checking in v4l2 input.

The capabilities flags that were used previously describe all
capabilities the physical device offers. This would cause devices
that are accessible through multiple device nodes to show up with
all device nodes while only one of the nodes might actually offer
the needed video capture capability.

If the device has more nodes the CAP_DEVICES_CAP flag might be set
in which case the device_caps field is filled with the capabilities
that only apply to that specific node that is opened.

plugins/linux-v4l2/v4l2-input.c

@@ -233,8 +233,6 @@ static void v4l2_device_list(obs_property_t prop, obs_data_t settings)
 {
 	DIR *dirp;
 	struct dirent *dp;
-	int fd;
-	struct v4l2_capability video_cap;
 	struct dstr device;
 	bool first = true;
 
@@ -247,6 +245,10 @@ static void v4l2_device_list(obs_property_t prop, obs_data_t settings)
 	dstr_init_copy(&device, "/dev/");
 
 	while ((dp = readdir(dirp)) != NULL) {
+		int fd;
+		uint32_t caps;
+		struct v4l2_capability video_cap;
+
 		if (dp->d_type == DT_DIR)
 			continue;
 
@@ -261,23 +263,33 @@ static void v4l2_device_list(obs_property_t prop, obs_data_t settings)
 		if (v4l2_ioctl(fd, VIDIOC_QUERYCAP, &video_cap) == -1) {
 			blog(LOG_INFO, "Failed to query capabilities for %s",
 			     device.array);
-		} else if (video_cap.capabilities & V4L2_CAP_VIDEO_CAPTURE) {
-			obs_property_list_add_string(prop,
-					(char *) video_cap.card,
-					device.array);
-			if (first) {
-				obs_data_set_string(settings,
-					"device_id", device.array);
-				first = false;
-			}
-			blog(LOG_INFO, "Found device '%s' at %s",
-			     video_cap.card, device.array);
+			close(fd);
+			continue;
 		}
-		else {
+
+		caps = (video_cap.capabilities & V4L2_CAP_DEVICE_CAPS)
+			? video_cap.device_caps
+			: video_cap.capabilities;
+
+		if (!(caps & V4L2_CAP_VIDEO_CAPTURE)) {
 			blog(LOG_INFO, "%s seems to not support video capture",
 			     device.array);
+			close(fd);
+			continue;
 		}
 
+		obs_property_list_add_string(prop, (char *) video_cap.card,
+				device.array);
+
+		if (first) {
+			obs_data_set_string(settings, "device_id",
+					device.array);
+			first = false;
+		}
+
+		blog(LOG_INFO, "Found device '%s' at %s", video_cap.card,
+				device.array);
+
 		close(fd);
 	}