hotplug: allow button timeout actions to trigger a subsequent timeout

This allows visual feedback when timeouts are reached.

In our case, there is a single button which on a normal press/release
will initiate DPP, but longer presses will first reboot then
factory reset. So users know they've held it down long enough,
it's nice to change the colour of the button.

This also fixes what seems to me a bug, in that you can attach
a timeout to a 'release' action but the timing was reset
(so you can't distinguish between a released timeout vs
a pressed timeout).

plug/hotplug.c

@@ -361,6 +361,17 @@ static struct cmd_handler {
 	},
 };
 
+/* This is a non-public handler used when a button event
+ * return a non-zero value, which is used as a timeout
+ * to subsequently call the same script.
+ */
+static struct cmd_handler BUTTON_TIMEOUT_HANDLER = {
+	.name = "button_timeout",
+	.handler = handle_exec,
+	.complete = handle_button_complete,
+};
+
+
 static void queue_next(void)
 {
 	struct cmd_queue *c;
@@ -441,13 +452,15 @@ static void handle_button_timeout(struct uloop_timeout *t)
 	blobmsg_add_string(&button_buf, "ACTION", "timeout");
 	snprintf(seen, sizeof(seen), "%d", b->seen);
 	blobmsg_add_string(&button_buf, "SEEN", seen);
-	queue_add(&handlers[HANDLER_EXEC], button_buf.head, b->data);
+	queue_add(&BUTTON_TIMEOUT_HANDLER, button_buf.head, b->data);
 	button_free(b);
 }
 
 static void handle_button_complete(struct blob_attr *msg, struct blob_attr *data, int ret)
 {
 	char *name = hotplug_msg_find_var(msg, "BUTTON");
+	char *action = hotplug_msg_find_var(msg, "ACTION");
+	char *seen = hotplug_msg_find_var(msg, "SEEN");
 	struct button_timeout *b;
 	int timeout = ret >> 8;
 
@@ -465,6 +478,13 @@ static void handle_button_complete(struct blob_attr *msg, struct blob_attr *data
 	b->name = strdup(name);
 	b->seen = timeout;
 
+	if (action && seen && (!strcmp(action, "timeout") || !strcmp(action, "released"))) {
+		/* If this happening due to a previous timeout or a released action,
+		 * then we should add on the previous SEEN time.
+		 */
+		b->seen += atoi(seen);
+	}
+
 	memcpy(b->data, data, blob_pad_len(data));
 	b->timeout.cb = handle_button_timeout;