Building ksmbd on Debian Buster (+bpo)

I am trying to build the ksmbd kernel module. I tried the tag version:

$ wget https://github.com/namjaejeon/ksmbd/archive/refs/tags/3.2.1.tar.gz$ tar xvfz 3.2.1.tar.gz$ cd ksmbd-3.2.1$ make[...]  CC [M]  /tmp/ksmbd-3.2.1/transport_tcp.o/tmp/ksmbd-3.2.1/transport_tcp.c: In function ‘create_socket’:/tmp/ksmbd-3.2.1/transport_tcp.c:484:10: error: incompatible type for argument 4 of ‘sock_setsockopt’          (char __user *)iface->name,          ^~~~~~~~~~~~~~~~~~~~~~~~~~

As well as the version from git/master:

$ git clone git@github.com:namjaejeon/ksmbd.git$ cd ksmbd$ makemake -C /lib/modules/5.10.0-0.bpo.7-amd64/build M=/tmp/ksmbd modulesmake[1]: Entering directory '/usr/src/linux-headers-5.10.0-0.bpo.7-amd64'make[3]: *** No rule to make target '/tmp/ksmbd/ksmbd_spnego_negtokeninit.asn1.c', needed by '/tmp/ksmbd/ksmbd_spnego_negtokeninit.asn1.o'.  Stop.make[2]: *** [/usr/src/linux-headers-5.10.0-0.bpo.7-common/Makefile:1845: /tmp/ksmbd] Error 2make[1]: *** [/usr/src/linux-headers-5.10.0-0.bpo.7-common/Makefile:185: __sub-make] Error 2make[1]: Leaving directory '/usr/src/linux-headers-5.10.0-0.bpo.7-amd64'make: *** [Makefile:47: all] Error 2

What's the trick to generate those *.asn1.c files ?

For reference:

$ cat Makefile [...]$(obj)/asn1.o: $(obj)/ksmbd_spnego_negtokeninit.asn1.h $(obj)/ksmbd_spnego_negtokentarg.asn1.h$(obj)/ksmbd_spnego_negtokeninit.asn1.o: $(obj)/ksmbd_spnego_negtokeninit.asn1.c $(obj)/ksmbd_spnego_negtokeninit.asn1.h$(obj)/ksmbd_spnego_negtokentarg.asn1.o: $(obj)/ksmbd_spnego_negtokentarg.asn1.c $(obj)/ksmbd_spnego_negtokentarg.asn1.h