what about " $(Q)@ " in toplevel Makefile???

[yihect]

Hi, all: 
  I'm reading top-level makefile of kernel version of 2.6.25, and 
being confused about "$(Q)@" in following lines:

    124 $(filter-out _all sub-make $(CURDIR)/Makefile, $(MAKECMDGOALS)) _all: 
sub-make
    125         $(Q)@:

  I know what's meaning for line 124, but what about line 125? Is it a command? 
I know the "$(Q)" indicates nothing if KBUILD_VERBOSE==1, and @ if 
KBUILD_VERBOSE
gave other values.

  Thanks.