Compile problem on Slackware64-15.0

[BusinessKid]

I have a usb dongle with an RTL8811CU chip (usb id: 0bda:c811), and tried compiling this for kernel 5.15.27. It pukes:
bash-5.1$ make
make -C /lib/modules/5.15.27/build M=/home/dec/tmp/rtw88-usb
make[1]: Entering directory '/usr/src/linux-5.15.27'
CC [M] /home/dec/tmp/rtw88-usb/mac80211.o
/home/dec/tmp/rtw88-usb/mac80211.c:812:35: error: initialization of ‘void (*)(struct ieee80211_hw *, struct ieee80211_vif *, struct ieee80211_prep_tx_info )’ from incompatible pointer type ‘void ()(struct ieee80211_hw *, struct ieee80211_vif , u16)’ {aka ‘void ()(struct ieee80211_hw *, struct ieee80211_vif *, short unsigned int)’} [-Werror=incompatible-pointer-types]
812 | .mgd_prepare_tx = rtw_ops_mgd_prepare_tx,
| ^~~~~~~~~~~~~~~~~~~~~~
/home/dec/tmp/rtw88-usb/mac80211.c:812:35: note: (near initialization for ‘rtw_ops.mgd_prepare_tx’)
cc1: some warnings being treated as errors
make[2]: *** [scripts/Makefile.build:277: /home/dec/tmp/rtw88-usb/mac80211.o] Error 1
make[1]: *** [Makefile:1868: /home/dec/tmp/rtw88-usb] Error 2
make[1]: Leaving directory '/usr/src/linux-5.15.27'
make: *** [Makefile:112: all] Error 2
bash-5.1$ sudo make clean
rm -f .o ..d *.a .ko ..cmd .mod *.order *.symvers .tmp_versions
bash-5.1$ make
make -C /lib/modules/5.15.27/build M=/home/dec/tmp/rtw88-usb
make[1]: Entering directory '/usr/src/linux-5.15.27'
CC [M] /home/dec/tmp/rtw88-usb/main.o
CC [M] /home/dec/tmp/rtw88-usb/mac80211.o
/home/dec/tmp/rtw88-usb/mac80211.c:812:35: error: initialization of ‘void ()(struct ieee80211_hw *, struct ieee80211_vif *, struct ieee80211_prep_tx_info )’ from incompatible pointer type ‘void ()(struct ieee80211_hw *, struct ieee80211_vif , u16)’ {aka ‘void ()(struct ieee80211_hw *, struct ieee80211_vif *, short unsigned int)’} [-Werror=incompatible-pointer-types]
812 | .mgd_prepare_tx = rtw_ops_mgd_prepare_tx,
| ^~~~~~~~~~~~~~~~~~~~~~
/home/dec/tmp/rtw88-usb/mac80211.c:812:35: note: (near initialization for ‘rtw_ops.mgd_prepare_tx’)
cc1: some warnings being treated as errors
make[2]: *** [scripts/Makefile.build:277: /home/dec/tmp/rtw88-usb/mac80211.o] Error 1
make[1]: *** [Makefile:1868: /home/dec/tmp/rtw88-usb] Error 2
make[1]: Leaving directory '/usr/src/linux-5.15.27'
make: *** [Makefile:112: all] Error 2

Because it was saying "some warnings as errors, I cleaned up and ran 'make -k' which continued past thyose errors and then failed this way:
… CC [M] /home/dec/tmp/rtw88-usb/usb.o
LD [M] /home/dec/tmp/rtw88-usb/rtw88_usb.o
make[2]: Target '__build' not remade because of errors.
make[1]: *** [Makefile:1868: /home/dec/tmp/rtw88-usb] Error 2
make[1]: Target '__all' not remade because of errors.
make[1]: Leaving directory '/usr/src/linux-5.15.27'
make: *** [Makefile:112: all] Error 2

I'm not a coder so I can't do much more really.