3 files changed, 88 insertions, 0 deletions

diff --git a/Documentation/video4linux/v4l2-framework.txt b/Documentation/video4linux/v4l2-framework.txt
index 493ffd1b1cf5..fe53177f0d3c 100644
--- a/Documentation/video4linux/v4l2-framework.txt
+++ b/Documentation/video4linux/v4l2-framework.txt
@@ -316,6 +316,18 @@ If the subdev driver intends to process video and integrate with the media
 framework, it must implement format related functionality using
 v4l2_subdev_pad_ops instead of v4l2_subdev_video_ops.
 
+In that case, the subdev driver may set the link_validate field to provide
+its own link validation function. The link validation function is called for
+every link in the pipeline where both of the ends of the links are V4L2
+sub-devices. The driver is still responsible for validating the correctness
+of the format configuration between sub-devices and video nodes.
+
+If link_validate op is not set, the default function
+v4l2_subdev_link_validate_default() is used instead. This function ensures
+that width, height and the media bus pixel code are equal on both source and
+sink of the link. Subdev drivers are also free to use this function to
+perform the checks mentioned above in addition to their own checks.
+
 A device (bridge) driver needs to register the v4l2_subdev with the
 v4l2_device:
 
diff --git a/drivers/media/video/v4l2-subdev.c b/drivers/media/video/v4l2-subdev.c
index 268d80584101..db6e859b93d4 100644
--- a/drivers/media/video/v4l2-subdev.c
+++ b/drivers/media/video/v4l2-subdev.c
@@ -387,6 +387,70 @@ const struct v4l2_file_operations v4l2_subdev_fops = {
         .poll = subdev_poll,
 };
 
+#ifdef CONFIG_MEDIA_CONTROLLER
+int v4l2_subdev_link_validate_default(struct v4l2_subdev *sd,
+                                      struct media_link *link,
+                                      struct v4l2_subdev_format *source_fmt,
+                                      struct v4l2_subdev_format *sink_fmt)
+{
+        if (source_fmt->format.width != sink_fmt->format.width
+            || source_fmt->format.height != sink_fmt->format.height
+            || source_fmt->format.code != sink_fmt->format.code)
+                return -EINVAL;
+
+        return 0;
+}
+EXPORT_SYMBOL_GPL(v4l2_subdev_link_validate_default);
+
+static int
+v4l2_subdev_link_validate_get_format(struct media_pad *pad,
+                                     struct v4l2_subdev_format *fmt)
+{
+        switch (media_entity_type(pad->entity)) {
+        case MEDIA_ENT_T_V4L2_SUBDEV:
+                fmt->which = V4L2_SUBDEV_FORMAT_ACTIVE;
+                fmt->pad = pad->index;
+                return v4l2_subdev_call(media_entity_to_v4l2_subdev(
+                                                pad->entity),
+                                        pad, get_fmt, NULL, fmt);
+        default:
+                WARN(1, "Driver bug! Wrong media entity type %d, entity %s\n",
+                     media_entity_type(pad->entity), pad->entity->name);
+                /* Fall through */
+        case MEDIA_ENT_T_DEVNODE_V4L:
+                return -EINVAL;
+        }
+}
+
+int v4l2_subdev_link_validate(struct media_link *link)
+{
+        struct v4l2_subdev *sink;
+        struct v4l2_subdev_format sink_fmt, source_fmt;
+        int rval;
+
+        rval = v4l2_subdev_link_validate_get_format(
+                link->source, &source_fmt);
+        if (rval < 0)
+                return 0;
+
+        rval = v4l2_subdev_link_validate_get_format(
+                link->sink, &sink_fmt);
+        if (rval < 0)
+                return 0;
+
+        sink = media_entity_to_v4l2_subdev(link->sink->entity);
+
+        rval = v4l2_subdev_call(sink, pad, link_validate, link,
+                                &source_fmt, &sink_fmt);
+        if (rval != -ENOIOCTLCMD)
+                return rval;
+
+        return v4l2_subdev_link_validate_default(
+                sink, link, &source_fmt, &sink_fmt);
+}
+EXPORT_SYMBOL_GPL(v4l2_subdev_link_validate);
+#endif /* CONFIG_MEDIA_CONTROLLER */
+
 void v4l2_subdev_init(struct v4l2_subdev *sd, const struct v4l2_subdev_ops *ops)
 {
         INIT_LIST_HEAD(&sd->list);
diff --git a/include/media/v4l2-subdev.h b/include/media/v4l2-subdev.h
index 7e850355a6f0..1c2318b15bd2 100644
--- a/include/media/v4l2-subdev.h
+++ b/include/media/v4l2-subdev.h
@@ -470,6 +470,11 @@ struct v4l2_subdev_pad_ops {
                              struct v4l2_subdev_selection *sel);
         int (*set_selection)(struct v4l2_subdev *sd, struct v4l2_subdev_fh *fh,
                              struct v4l2_subdev_selection *sel);
+#ifdef CONFIG_MEDIA_CONTROLLER
+        int (*link_validate)(struct v4l2_subdev *sd, struct media_link *link,
+                             struct v4l2_subdev_format *source_fmt,
+                             struct v4l2_subdev_format *sink_fmt);
+#endif /* CONFIG_MEDIA_CONTROLLER */
 };
 
 struct v4l2_subdev_ops {
@@ -602,6 +607,13 @@ static inline void *v4l2_get_subdev_hostdata(const struct v4l2_subdev *sd)
         return sd->host_priv;
 }
 
+#ifdef CONFIG_MEDIA_CONTROLLER
+int v4l2_subdev_link_validate_default(struct v4l2_subdev *sd,
+                                      struct media_link *link,
+                                      struct v4l2_subdev_format *source_fmt,
+                                      struct v4l2_subdev_format *sink_fmt);
+int v4l2_subdev_link_validate(struct media_link *link);
+#endif /* CONFIG_MEDIA_CONTROLLER */
 void v4l2_subdev_init(struct v4l2_subdev *sd,
                       const struct v4l2_subdev_ops *ops);