Roku DIAL is only able to launch/exit the channel, is there inputs too?

Currently, from any DIAL client, after getting the 'Application-URL' using M_SEARCH and 

POST http://host:8060/dial/dial_title, with URL-encoded params ("dial_payload"), we are able to launch the channel on Roku device. And, also DELETE http://host:8060/dial/dial_title/run will exit the channel.

But, how can we send the params ("dial_payload") to the Roku channel while the channel is already launched and running via DIAL?