SDL_PushEvent (3) - Linux Manuals
SDL_PushEvent: Pushes an event onto the event queue
NAMESDL_PushEvent - Pushes an event onto the event queue
The event queue can actually be used as a two way communication channel. Not only can events be read from the queue, but the user can also push their own events onto it. event is a pointer to the event structure you wish to push onto the queue.
Pushing device input events onto the queue doesn't modify the state of the device within SDL.
SDL_PollEvent, SDL_PeepEvents, SDL_Event