Switching video port coding type from unused to used.

What does the standard say about the ability to switch a video port from a certain video coding type (color format unused)
to a certain color format (coding unused), using one call to OMX_SetParameter and either index OMX_VIDEO_PORTDEFINITIONTYPE or OMX_VIDEO_PARAM_PORTFORMATTYPE whilst both eCompressionFormat and eColorFormat is set accordingly.

Is it so that a port is not supposed to be able to switch say, output from YUV (no coding type) to MPEG (no color format)?