expo: Add some scene fields needed for text entry

Add the CLI state, a buffer to hold the old value of the text being
edited and a place to save vidconsole entry context. These will be use
by the textline object.

Set an upper limit on the maximum number of characters in a textline
object supported by expo, at least for now.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/boot/scene.c b/boot/scene.c
index 314dd7c..0b44a13 100644
--- a/boot/scene.c
+++ b/boot/scene.c
@@ -32,6 +32,14 @@
 		return log_msg_ret("name", -ENOMEM);
 	}
 
+	abuf_init(&scn->buf);
+	if (!abuf_realloc(&scn->buf, EXPO_MAX_CHARS + 1)) {
+		free(scn->name);
+		free(scn);
+		return log_msg_ret("buf", -ENOMEM);
+	}
+	abuf_init(&scn->entry_save);
+
 	INIT_LIST_HEAD(&scn->obj_head);
 	scn->id = resolve_id(exp, id);
 	scn->expo = exp;
@@ -57,6 +65,8 @@
 	list_for_each_entry_safe(obj, next, &scn->obj_head, sibling)
 		scene_obj_destroy(obj);
 
+	abuf_uninit(&scn->entry_save);
+	abuf_uninit(&scn->buf);
 	free(scn->name);
 	free(scn);
 }
diff --git a/include/expo.h b/include/expo.h
index c16b3dd..a535bc1 100644
--- a/include/expo.h
+++ b/include/expo.h
@@ -7,11 +7,14 @@
 #ifndef __EXPO_H
 #define __EXPO_H
 
+#include <abuf.h>
 #include <dm/ofnode_decl.h>
 #include <linux/list.h>
 
 struct udevice;
 
+#include <cli.h>
+
 /**
  * enum expoact_type - types of actions reported by the expo
  *
@@ -121,6 +124,9 @@
  * @id: ID number of the scene
  * @title_id: String ID of title of the scene (allocated)
  * @highlight_id: ID of highlighted object, if any
+ * @cls: cread state to use for input
+ * @buf: Buffer for input
+ * @entry_save: Buffer to hold vidconsole text-entry information
  * @sibling: Node to link this scene to its siblings
  * @obj_head: List of objects in the scene
  */
@@ -130,6 +136,9 @@
 	uint id;
 	uint title_id;
 	uint highlight_id;
+	struct cli_line_state cls;
+	struct abuf buf;
+	struct abuf entry_save;
 	struct list_head sibling;
 	struct list_head obj_head;
 };
@@ -180,6 +189,11 @@
 	SCENEOF_OPEN	= 1 << 2,
 };
 
+enum {
+	/* Maximum number of characters allowed in an line editor */
+	EXPO_MAX_CHARS		= 250,
+};
+
 /**
  * struct scene_obj - information about an object in a scene
  *