media: v4l2-subdev: Add v4l2_subdev_s_stream_helper() function

The v4l2_subdev_s_stream_helper() helper can be used by subdevs that
implement the stream-aware .enable_streams() and .disable_streams()
operations to implement .s_stream(). This is limited to subdevs that
have a single source pad.
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Reviewed-by: Jacopo Mondi <jacopo@jmondi.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>

drivers/media/v4l2-core/v4l2-subdev.c

@@ -1967,6 +1967,46 @@ int v4l2_subdev_disable_streams(struct v4l2_subdev *sd, u32 pad,
 }
 EXPORT_SYMBOL_GPL(v4l2_subdev_disable_streams);
 
+int v4l2_subdev_s_stream_helper(struct v4l2_subdev *sd, int enable)
+{
+	struct v4l2_subdev_state *state;
+	struct v4l2_subdev_route *route;
+	struct media_pad *pad;
+	u64 source_mask = 0;
+	int pad_index = -1;
+
+	/*
+	 * Find the source pad. This helper is meant for subdevs that have a
+	 * single source pad, so failures shouldn't happen, but catch them
+	 * loudly nonetheless as they indicate a driver bug.
+	 */
+	media_entity_for_each_pad(&sd->entity, pad) {
+		if (pad->flags & MEDIA_PAD_FL_SOURCE) {
+			pad_index = pad->index;
+			break;
+		}
+	}
+
+	if (WARN_ON(pad_index == -1))
+		return -EINVAL;
+
+	/*
+	 * As there's a single source pad, just collect all the source streams.
+	 */
+	state = v4l2_subdev_lock_and_get_active_state(sd);
+
+	for_each_active_route(&state->routing, route)
+		source_mask |= BIT_ULL(route->source_stream);
+
+	v4l2_subdev_unlock_state(state);
+
+	if (enable)
+		return v4l2_subdev_enable_streams(sd, pad_index, source_mask);
+	else
+		return v4l2_subdev_disable_streams(sd, pad_index, source_mask);
+}
+EXPORT_SYMBOL_GPL(v4l2_subdev_s_stream_helper);
+
 #endif /* CONFIG_VIDEO_V4L2_SUBDEV_API */
 
 #endif /* CONFIG_MEDIA_CONTROLLER */

include/media/v4l2-subdev.h

@@ -1731,6 +1731,23 @@ int v4l2_subdev_enable_streams(struct v4l2_subdev *sd, u32 pad,
 int v4l2_subdev_disable_streams(struct v4l2_subdev *sd, u32 pad,
 				u64 streams_mask);
 
+/**
+ * v4l2_subdev_s_stream_helper() - Helper to implement the subdev s_stream
+ *	operation using enable_streams and disable_streams
+ * @sd: The subdevice
+ * @enable: Enable or disable streaming
+ *
+ * Subdevice drivers that implement the streams-aware
+ * &v4l2_subdev_pad_ops.enable_streams and &v4l2_subdev_pad_ops.disable_streams
+ * operations can use this helper to implement the legacy
+ * &v4l2_subdev_video_ops.s_stream operation.
+ *
+ * This helper can only be used by subdevs that have a single source pad.
+ *
+ * Return: 0 on success, or a negative error code otherwise.
+ */
+int v4l2_subdev_s_stream_helper(struct v4l2_subdev *sd, int enable);
+
 #endif /* CONFIG_VIDEO_V4L2_SUBDEV_API */
 
 #endif /* CONFIG_MEDIA_CONTROLLER */