expo: Allow setting the start of the dynamic-ID range

Provide a way to set this value so that it is easy to separate the
statically allocated IDs (generated by the caller) from those
generated dynamically by expo itself.

Signed-off-by: Simon Glass <sjg@chromium.org>

boot/expo.c

@@ -56,6 +56,21 @@ void expo_destroy(struct expo *exp)
 	free(exp);
 }
 
+uint resolve_id(struct expo *exp, uint id)
+{
+	if (!id)
+		id = exp->next_id++;
+	else if (id >= exp->next_id)
+		exp->next_id = id + 1;
+
+	return id;
+}
+
+void expo_set_dynamic_start(struct expo *exp, uint dyn_start)
+{
+	exp->next_id = dyn_start;
+}
+
 int expo_str(struct expo *exp, const char *name, uint id, const char *str)
 {
 	struct expo_string *estr;

boot/scene.c

@@ -18,16 +18,6 @@
 #include <linux/input.h>
 #include "scene_internal.h"
 
-uint resolve_id(struct expo *exp, uint id)
-{
-	if (!id)
-		id = exp->next_id++;
-	else if (id >= exp->next_id)
-		exp->next_id = id + 1;
-
-	return id;
-}
-
 int scene_new(struct expo *exp, const char *name, uint id, struct scene **scnp)
 {
 	struct scene *scn;

doc/develop/expo.rst

@@ -85,6 +85,9 @@ or even the IDs of objects. Programmatic creation of many items in a loop can be
 handled by allocating space in the enum for a maximum number of items, then
 adding the loop count to the enum values to obtain unique IDs.
 
+Where dynamic IDs are need, use expo_set_dynamic_start() to set the start value,
+so that they are allocated above the starting (enum) IDs.
+
 All text strings are stored in a structure attached to the expo, referenced by
 a text ID. This makes it easier at some point to implement multiple languages or
 to support Unicode strings.

include/expo.h

@@ -257,6 +257,25 @@ int expo_new(const char *name, void *priv, struct expo **expp);
  */
 void expo_destroy(struct expo *exp);
 
+/**
+ * expo_set_dynamic_start() - Set the start of the 'dynamic' IDs
+ *
+ * It is common for a set of 'static' IDs to be used to refer to objects in the
+ * expo. These typically use an enum so that they are defined in sequential
+ * order.
+ *
+ * Dynamic IDs (for objects not in the enum) are intended to be used for
+ * objects to which the code does not need to refer. These are ideally located
+ * above the static IDs.
+ *
+ * Use this function to set the start of the dynamic range, making sure that the
+ * value is higher than all the statically allocated IDs.
+ *
+ * @exp: Expo to update
+ * @dyn_start: Start ID that expo should use for dynamic allocation
+ */
+void expo_set_dynamic_start(struct expo *exp, uint dyn_start);
+
 /**
  * expo_str() - add a new string to an expo
  *