On Dienstag, 8. Februar 2022 06:45:45 CET Song Liu wrote: Hi Song, > > -struct raid6_calls raid6_call; > > +extern struct raid6_calls raid6_call; > > Can we just remove this line? oh yes indeed, it is already declared in the header file. that is much simpler. I've sent a PATCH v2 just now. Thank you, Dirk