Error when compiling Driver with DKMS

[v01ded]

Getting the following errors when compiling the driver. My setup:

uname -r
5.4.0-0.bpo.4-amd64

Tried the temporary workaround suggested here:

Just a temporary workaround, but you can still compile and install the driver if you add the following line to the top of the Makefile:
USER_EXTRA_CFLAGS=-Wno-error=incompatible-pointer-types

Make[2]:` *** [/usr/src/linux-headers-5.4.0-0.bpo.4-common/Makefile:1665: /var/lib/dkms/rtl8821CU/5.8.1/build] Error 2
make[1]: *** [/usr/src/linux-headers-5.4.0-0.bpo.4-common/Makefile:179: sub-make] Error 2
make[1]: Leaving directory '/usr/src/linux-headers-5.4.0-0.bpo.4-amd64'
make: *** [Makefile:2336: modules] Error 2
/var/lib/dkms/rtl8821CU/5.8.1/build/os_dep/linux/os_intfs.c:1707:22: error: initialization of ‘u16 (*)(struct net_device *, struct sk_buff *, struct net_device *)’ {aka ‘short unsigned int (*)(struct net_device *, struct sk_buff *, struct net_device *)’} from incompatible pointer type ‘u16 (*)(struct net_device *, struct sk_buff *, struct net_device *, u16 (*)(struct net_device *, struct sk_buff *, struct net_device *))’ {aka ‘short unsigned int (*)(struct net_device *, struct sk_buff *, struct net_device *, short unsigned int (*)(struct net_device *, struct sk_buff *, struct net_device *))’} [-Werror=incompatible-pointer-types]
  .ndo_select_queue = rtw_select_queue,
                      ^~~~~~~~~~~~~~~~
/var/lib/dkms/rtl8821CU/5.8.1/build/os_dep/linux/os_intfs.c:1707:22: note: (near initialization for ‘rtw_netdev_ops.ndo_select_queue’)
/var/lib/dkms/rtl8821CU/5.8.1/build/os_dep/linux/os_intfs.c:3058:22: error: initialization of ‘u16 (*)(struct net_device *, struct sk_buff *, struct net_device *)’ {aka ‘short unsigned int (*)(struct net_device *, struct sk_buff *, struct net_device *)’} from incompatible pointer type ‘u16 (*)(struct net_device *, struct sk_buff *, struct net_device *, u16 (*)(struct net_device *, struct sk_buff *, struct net_device *))’ {aka ‘short unsigned int (*)(struct net_device *, struct sk_buff *, struct net_device *, short unsigned int (*)(struct net_device *, struct sk_buff *, struct net_device *))’} [-Werror=incompatible-pointer-types]
  .ndo_select_queue = rtw_select_queue,
                      ^~~~~~~~~~~~~~~~
/var/lib/dkms/rtl8821CU/5.8.1/build/os_dep/linux/os_intfs.c:3058:22: note: (near initialization for ‘rtw_netdev_vir_if_ops.ndo_select_queue’)
  CC [M]  /var/lib/dkms/rtl8821CU/5.8.1/build/os_dep/linux/usb_ops_linux.o
cc1: some warnings being treated as errors
make[3]: *** [/usr/src/linux-headers-5.4.0-0.bpo.4-common/scripts/Makefile.build:271: /var/lib/dkms/rtl8821CU/5.8.1/build/os_dep/linux/os_intfs.o] Error 1
make[3]: *** Waiting for unfinished jobs....
make[2]: *** [/usr/src/linux-headers-5.4.0-0.bpo.4-common/Makefile:1665: /var/lib/dkms/rtl8821CU/5.8.1/build] Error 2
make[1]: *** [/usr/src/linux-headers-5.4.0-0.bpo.4-common/Makefile:179: sub-make] Error 2
make[1]: Leaving directory '/usr/src/linux-headers-5.4.0-0.bpo.4-amd64'
make: *** [Makefile:2336: modules] Error 2

Any idea to relve this issue will be very much appreciated! :)

Stay safe and healthy.
Stanley

[v01ded]

Found a solution to solve the error and gotthe driver complied successfully. As I'm not a programmer and do not know the impact on rest of the code , use it at your own risk

Open file /var/lib/dkms/rtl8821CU/5.8.1/source/os_dep/linux/os_intfs.c

nano /var/lib/dkms/rtl8821CU/5.8.1/source/os_dep/linux/os_intfs.c

Look for the following section of code:

static u16 rtw_select_queue(struct net_device *dev, struct sk_buff *skb
#if LINUX_VERSION_CODE >= KERNEL_VERSION(3, 13, 0)
	#if LINUX_VERSION_CODE >= KERNEL_VERSION(4, 19, 0)
	, struct net_device *sb_dev
	#else
	, void *accel_priv
	#endif
	#if LINUX_VERSION_CODE >= KERNEL_VERSION(3, 14, 0)
	, select_queue_fallback_t fallback
	#endif
#endif
)

Replace with

static u16 rtw_select_queue(struct net_device *dev, struct sk_buff *skb
#if LINUX_VERSION_CODE >= KERNEL_VERSION(3, 13, 0)
        #if LINUX_VERSION_CODE >= KERNEL_VERSION(4, 19, 0)
        , struct net_device *sb_dev
        #else
        , void *accel_priv
        #endif
        #if ((LINUX_VERSION_CODE >= KERNEL_VERSION(3, 14, 0)) && (LINUX_VERSION_CODE < KERNEL_VERSION(5, 2, 0)))
        , select_queue_fallback_t fallback
        #endif

#endif
)

[BlueHeart0621]

make error!
./include/linux/slub_def.h:112:28: error: field ‘memcg_params’ has incomplete type 112 | struct memcg_cache_params memcg_params;