Here is a list of all documented files with brief descriptions:

xtmrctr.c
xtmrctr.h
xtmrctr_g.c
xtmrctr_i.h
xtmrctr_intr.c
xtmrctr_l.c
xtmrctr_l.h
xtmrctr_options.c
xtmrctr_selftest.c
xtmrctr_sinit.c
xtmrctr_stats.c