Confused with MCP of gm-1.5 and gm-1.4pre48 !

Hello:
  We have been using gm-1.4pre48 on our cluster before, and now using gm-1.5.
It seems that the MCP directory of gm-1.4pre48 has gm_sdma.h/gm_send.h/
gm_recv.h/gm_rdma.h files for SDMA/SEND/RECV/RDMA DMA engines respectively. But 
for gm-1.5, the MCP directory added gm_sdma.c/gm_send.c/gm_recv.c/gm_rdma.c, that
is, it includes gm_sdma.h/gm_sdma.c, gm_send.h/gm_send.c,gm_recv.h/gm_recv.c, and gm_rdma.h/gm_rdma.c for SDMA/SEND/RECV/RDMA DMA engines. Some Mark_LABEL micros in the *.h servers as handlers for recving/sending messages. But for the added files: *.c, there are also some function such as L__START_poll_sdma(...), which seems mainly the same as the correspondent *.h files.Then what's the use of these *.c files, since in the gm-1.4pre48, no such *.c files
available. 
  I'm not experienced with the compilation of MCP/GM. Could anyboby
give some explanation ? Any information would be greatly appreciated!

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Best regards
Geoge Zhang