this was built from stock 2.4.2 kernel.
gcc -D__KERNEL__ -I/usr/src/RPM/BUILD/linux/include -Wall -Wstrict-prototypes
-O2 -fomit-frame-pointer -fno-strict-aliasing -pipe
-mpreferred-stack-boundary=2 -march=i586 -DMODULE -DMODVERSIONS -include
/usr/src/RPM/BUILD/linux/include/linux/modversions.h -c -o mkiss.o mkiss.c
gcc -D__KERNEL__ -I/usr/src/RPM/BUILD/linux/include -Wall -Wstrict-prototypes
-O2 -fomit-frame-pointer -fno-strict-aliasing -pipe
-mpreferred-stack-boundary=2 -march=i586 -DMODULE -DMODVERSIONS -include
/usr/src/RPM/BUILD/linux/include/linux/modversions.h -c -o 6pack.o 6pack.c
6pack.c: In function `sixpack_init_driver':
6pack.c:714: `KMALLOC_MAXSIZE' undeclared (first use in this function)
6pack.c:714: (Each undeclared identifier is reported only once
6pack.c:714: for each function it appears in.)
make[2]: *** [6pack.o] Error 1
make[2]: Leaving directory `/usr/src/RPM/BUILD/linux/drivers/net/hamradio'
make[1]: *** [_modsubdir_net/hamradio] Error 2
make[1]: Leaving directory `/usr/src/RPM/BUILD/linux/drivers'
make: *** [_mod_drivers] Error 2
Thanks
Jorg