Here is more information about the nature of the build failure.
root@smp1:~# apt-get --reinstall install sl-modem-dkms
Reading package lists... Done
Building dependency tree
Reading state information... Done
0 upgraded, 0 newly installed, 1 reinstalled, 0 to remove and 3 not upgraded.
Need to get 0 B/205 kB of archives.
After this operation, 0 B of additional disk space will be used.
(Reading database ... 176139 files and directories currently installed.)
Preparing to unpack .../sl-modem-dkms_2.9.11~20110321-12_i386.deb ...
------------------------------
Deleting module version: 2.9.11~20110321
completely from the DKMS tree.
------------------------------
Done.
Unpacking sl-modem-dkms (2.9.11~20110321-12) over (2.9.11~20110321-12) ...
Setting up sl-modem-dkms (2.9.11~20110321-12) ...
Loading new sl-modem-2.9.11~20110321 DKMS files...
Building for 4.9.2-1custom01-686-pae
Building initial module for 4.9.2-1custom01-686-pae
Error! Build of slusb.ko failed for: 4.9.2-1custom01-686-pae (i686)
Consult the make.log in the build directory
/var/lib/dkms/sl-modem/2.9.11~20110321/build/ for more information.
DKMS make.log for sl-modem-2.9.11~20110321 for kernel 4.9.2-1custom01-686-pae
(i686)
Fri Feb 10 19:07:40 EST 2017
make: Entering directory '/var/lib/dkms/sl-modem/2.9.11~20110321/build/drivers'
doing %.o: %.c
cc -Wall -pipe -O3 -fomit-frame-pointer -D__KERNEL__ -DMODULE -DEXPORT_SYMTAB
`test -f /lib/modules/4.9.2-1custom01-686-pae/build/include/linux/modversions.h
&& echo -DMODVERSIONS --include
/lib/modules/4.9.2-1custom01-686-pae/build/include/linux/modversions.h
-I/lib/modules/4.9.2-1custom01-686-pae/build/include` -I. -I./../modem -o
amrmo_init.o -c amrmo_init.c
amrmo_init.c:57:26: fatal error: linux/module.h: No such file or directory
#include <linux/module.h>
^
compilation terminated.
Makefile:128: recipe for target 'amrmo_init.o' failed
make: *** [amrmo_init.o] Error 1
make: Leaving directory '/var/lib/dkms/sl-modem/2.9.11~20110321/build/drivers'
make: Entering directory
'/var/lib/dkms/sl-modem/2.9.11~20110321/build/ungrab-winmodem'
make modules -C /lib/modules/4.9.2-1custom01-686-pae/build
SUBDIRS=/var/lib/dkms/sl-modem/2.9.11~20110321/build/ungrab-winmodem
make[1]: Entering directory '/usr/src/linux-source-4.9'
--
.''`. Stephen Powell <zlinux...@fastmail.com>
: :' :
`. `'`
`-
