樹莓派使用 comfast 無線網卡

# 前緣

去年在淘寶上買了一個無線網卡，由于是給辦公室電腦用，系統是 Windows 10 ，就買了個便宜的，只支持 Windows 和 MAC ，

期間也嘗試過插在蝸牛星際上(Ubuntu Server 18.04)，只看到多了一個 usb 設備，并不能產生無線網路介面，問淘寶賣家，給了一個驅動鏈接

CF-811AC驅動下載地址：http://www.comfast.cn/index.php?m=content&c=index&a=show&catid=30&id=335

下載下來也沒編過，結果就沒在 Linux上用上，

# 再續

最近在研究 Wi-Fi ，又把它掏了出來，看看能不能在 Linux 上用起來，

直接插在樹莓派上，情況還是和之前在蝸牛星際上一樣，只顯示多了一個 usb 設備，并沒有無線網路介面產生，

網上搜到了這篇教程 《Linux安裝comfast 811AC usb網卡驅動》 ，就跟著上面的步驟下載編譯，

由于樹莓派里面沒有裝內核頭檔案，所以編譯報錯，解決辦法，安裝內核頭檔案

sudo apt install raspberrypi-kernel-headers

注意，ARM 架構的話要執行 README.md 里的三句指令

sudo cp /lib/modules/$(uname -r)/build/arch/arm/Makefile /lib/modules/$(uname -r)/build/arch/arm/Makefile.$(date +%Y%m%d%H%M)
sudo sed -i 's/-msoft-float//' /lib/modules/$(uname -r)/build/arch/arm/Makefile
sudo ln -s /lib/modules/$(uname -r)/build/arch/arm /lib/modules/$(uname -r)/build/arch/armv7l

繼續編譯，又報錯

/home/pi/project/c/DRIVERS/rtl8821CU/core/rtw_debug.c: In function ‘dump_drv_version’:
/home/pi/project/c/DRIVERS/rtl8821CU/core/rtw_debug.c:45:62: error: macro "__DATE__" might prevent reproducible builds [-Werror=date-time]
  RTW_PRINT_SEL(sel, "build time: %s %s\n", __DATE__, __TIME__);
                                                              ^
/home/pi/project/c/DRIVERS/rtl8821CU/core/rtw_debug.c:45:62: error: macro "__TIME__" might prevent reproducible builds [-Werror=date-time]
/home/pi/project/c/DRIVERS/rtl8821CU/core/rtw_debug.c:45:62: error: macro "__DATE__" might prevent reproducible builds [-Werror=date-time]
/home/pi/project/c/DRIVERS/rtl8821CU/core/rtw_debug.c:45:62: error: macro "__TIME__" might prevent reproducible builds [-Werror=date-time]
cc1: some warnings being treated as errors
make[2]: *** [scripts/Makefile.build:304: /home/pi/project/c/DRIVERS/rtl8821CU/core/rtw_debug.o] Error 1
make[1]: *** [Makefile:1522: _module_/home/pi/project/c/DRIVERS/rtl8821CU] Error 2
make[1]: Leaving directory '/usr/src/linux-headers-4.19.97-v7+'
make: *** [Makefile:2217: modules] Error 2

提示沒有 __TIME__ 、 __DATE__ 宏，grep查看一下哪些地方使用了這些宏

pi@raspberrypi:~/project/c/DRIVERS/rtl8821CU $ grep -rn "__DATE__"
core/rtw_debug.c:45:	RTW_PRINT_SEL(sel, "build time: %s %s\n", __DATE__, __TIME__);

本來想給它手動改個時間日期填上，發現只有一句，并且感覺不是什么重要的陳述句，就直接注釋掉了

void dump_drv_version(void *sel)
{
        RTW_PRINT_SEL(sel, "%s %s\n", DRV_NAME, DRIVERVERSION);
        //RTW_PRINT_SEL(sel, "build time: %s %s\n", __DATE__, __TIME__);
}

編譯通過，安裝到內核

pi@raspberrypi:~/project/c/DRIVERS/rtl8821CU$ sudo modprobe 8821cu

查看驅動是否安裝成功

pi@raspberrypi:~/project/c/DRIVERS/rtl8821CU$ lsmod
Module                  Size  Used by
8821cu               2404352  0
r8188eu               438272  0
lib80211               16384  1 r8188eu
nls_ascii              16384  1
btsdio                 20480  0
bluetooth             557056  1 btsdio
ecdh_generic           16384  1 bluetooth
ecc                    36864  1 ecdh_generic
brcmfmac              385024  0
brcmutil               24576  1 brcmfmac
bcm2835_v4l2           45056  0
bcm2835_mmal_vchiq     40960  1 bcm2835_v4l2
vc_sm_cma              45056  1 bcm2835_mmal_vchiq
v4l2_common            16384  1 bcm2835_v4l2
videobuf2_vmalloc      20480  1 bcm2835_v4l2
videobuf2_memops       20480  1 videobuf2_vmalloc
cfg80211              692224  3 r8188eu,brcmfmac,8821cu
videobuf2_v4l2         28672  1 bcm2835_v4l2

出現了 8821cu 說明驅動模塊載入內核成功，

接著，拔插無線網卡，看到無線網卡已經被成功驅動，并且可以正常使用了，wlan0 是樹莓派自帶的無線網卡，wlan1 就是 comfast 無線網卡，

pi@raspberrypi:~/project/c/DRIVERS/rtl8821CU $ ifconfig 
eth0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 192.168.2.116  netmask 255.255.255.0  broadcast 192.168.2.255
        inet6 fe80::c294:4582:7476:70d5  prefixlen 64  scopeid 0x20<link>
        ether b8:27:eb:8a:bc:f4  txqueuelen 1000  (Ethernet)
        RX packets 1122  bytes 123550 (120.6 KiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 849  bytes 280450 (273.8 KiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

lo: flags=73<UP,LOOPBACK,RUNNING>  mtu 65536
        inet 127.0.0.1  netmask 255.0.0.0
        inet6 ::1  prefixlen 128  scopeid 0x10<host>
        loop  txqueuelen 1000  (Local Loopback)
        RX packets 172  bytes 14084 (13.7 KiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 172  bytes 14084 (13.7 KiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

wlan0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 192.168.2.211  netmask 255.255.255.0  broadcast 192.168.2.255
        inet6 fe80::7186:984c:b898:8ef3  prefixlen 64  scopeid 0x20<link>
        ether de:88:c4:e0:37:89  txqueuelen 1000  (Ethernet)
        RX packets 330  bytes 42876 (41.8 KiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 225  bytes 31375 (30.6 KiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

wlan1: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 192.168.2.178  netmask 255.255.255.0  broadcast 192.168.2.255
        inet6 fe80::5ca7:f148:acc7:565a  prefixlen 64  scopeid 0x20<link>
        ether 6e:b8:f3:2a:7b:76  txqueuelen 1000  (Ethernet)
        RX packets 462  bytes 76567 (74.7 KiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 245  bytes 34741 (33.9 KiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0