Question please, could someone share the meaning of the parameters for drmModeSetPlane in libdrm?

int drmModeSetPlane(int fd, uint32_t plane_id, uint32_t crtc_id,

                                    uint32_t fb_id, uint32_t flags,

                                    int32_t crtc_x, int32_t crtc_y,

                                    uint32_t crtc_w, uint32_t crtc_h,

                                    uint32_t src_x, uint32_t src_y,

                                    uint32_t src_w, uint32_t src_h)

My problem is, whatever value I set, the video is not full screen mode,

Anything I missed?

Thanks

William