now ,I know .The depmod is just build the moudle dependencies . And the next is to use modporbe to insert the modul .
the g_mass_storage has been insert by the document 035-Loadable-Module-Test.txt .
But I have the same problem when I do next :
root@imx6qdlsolo:~# modprobe libcomposite
libcomposite: version magic '3.14.28-1.0.0_ga+g91cf351 SMP preempt mod_unload modversions ARMv7 p2v8 ' should be '3.14.28-1.0.0_ga-mfgtool+g91cf351 SMP preempt mod_unload modversions ARMv6 p2v8 '
modprobe: ERROR: could not insert 'libcomposite': Exec format error