[media] v4l: subdev: Add pad config allocator and init

Add a new subdev operation to initialize a subdev pad config array, and
a helper function to allocate and initialize the array. This can be used
by bridge drivers to implement try format based on subdev pad
operations.

Signed-off-by: Laurent Pinchart <laurent.pinchart@linaro.org>
Acked-by: Vaibhav Hiremath <vaibhav.hiremath@linaro.org>
Acked-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
diff --git a/include/media/v4l2-subdev.h b/include/media/v4l2-subdev.h
index 11e2dfe..32fc7a4 100644
--- a/include/media/v4l2-subdev.h
+++ b/include/media/v4l2-subdev.h
@@ -572,6 +572,7 @@
 /**
  * struct v4l2_subdev_pad_ops - v4l2-subdev pad level operations
  *
+ * @init_cfg: initialize the pad config to default values
  * @enum_mbus_code: callback for VIDIOC_SUBDEV_ENUM_MBUS_CODE ioctl handler
  *		    code.
  * @enum_frame_size: callback for VIDIOC_SUBDEV_ENUM_FRAME_SIZE ioctl handler
@@ -607,6 +608,8 @@
  *                  may be adjusted by the subdev driver to device capabilities.
  */
 struct v4l2_subdev_pad_ops {
+	int (*init_cfg)(struct v4l2_subdev *sd,
+			struct v4l2_subdev_pad_config *cfg);
 	int (*enum_mbus_code)(struct v4l2_subdev *sd,
 			      struct v4l2_subdev_pad_config *cfg,
 			      struct v4l2_subdev_mbus_code_enum *code);
@@ -801,7 +804,12 @@
 				      struct v4l2_subdev_format *source_fmt,
 				      struct v4l2_subdev_format *sink_fmt);
 int v4l2_subdev_link_validate(struct media_link *link);
+
+struct v4l2_subdev_pad_config *
+v4l2_subdev_alloc_pad_config(struct v4l2_subdev *sd);
+void v4l2_subdev_free_pad_config(struct v4l2_subdev_pad_config *cfg);
 #endif /* CONFIG_MEDIA_CONTROLLER */
+
 void v4l2_subdev_init(struct v4l2_subdev *sd,
 		      const struct v4l2_subdev_ops *ops);