Linux内核编译初探—USB转网口驱动模块config文件配置方法
最近在调试USB转网口，涉及到Linux内核编译配置文件的更改，记录一下调试过程。
首先需要了解USB设备接入后系统的识别信息，打印内核日志：
root@MyDevice:/# dmesg | tail -20
[ 5364.325642] usb 1-1.1: new high-speed USB device number 5 using xhci-hcd
[ 5364.426138] usb 1-1.1: New USB device found, idVendor=0bda, idProduct=8152
[ 5364.426145] usb 1-1.1: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[ 5364.426148] usb 1-1.1: Product: USB 10/100 LAN
[ 5364.426152] usb 1-1.1: Manufacturer: Realtek
[ 5364.426155] usb 1-1.1: SerialNumber: 00E04C3607A9注意idProduct和Manufacturer内容，我用的这款USB转网口设备嵌入的是瑞昱的8152网口芯片。
进入Linux内核源码的kernel目录执行
make menuconfig进入到图形化配置界面，依次键选[Device Drivers -> Network device support -> USB Network Adapters]
找到 Realtek RTL8152/RTL8153 Based USB Ethernet Adapters选项使能即可。
以上选项信息参考博文：https://www.eefocus.com/toradex/blog/16-12/401923_7db7d.html
然而，编译出的内核版本验证未成功，进入menuconfig图形界面发现勾选已失效（无法正常保存勾选），因此在内核源码目录下寻找config文件进行手动更改配置项
.../configs/.../normal_kernel.config
查看代码
...
CONFIG_USB_NET_DRIVERS=y
# CONFIG_USB_CATC is not set
# CONFIG_USB_KAWETH is not set
# CONFIG_USB_PEGASUS is not set
#CONFIG_USB_RTL8150 is not set
#CONFIG_USB_RTL8152 is not set
# CONFIG_USB_LAN78XX is not set
CONFIG_USB_USBNET=y
CONFIG_USB_NET_AX8817X=y
CONFIG_USB_NET_AX88179_178A=y
CONFIG_USB_NET_CDCETHER=y
# CONFIG_USB_NET_CDC_EEM is not set
...将CONFIG_USB_RTL8150和CONFIG_USB_RTL8152设为使能，进入menuconfig查看相应配置项，已更新为勾选。
制作内核版本，烧写至设备后上电启动，dmesg查看USB接口信息：
[ 471.409739] usb 1-1.1: new high-speed USB device number 4 using xhci-hcd
[ 471.510346] usb 1-1.1: New USB device found, idVendor=0bda, idProduct=8152
[ 471.510353] usb 1-1.1: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[ 471.510357] usb 1-1.1: Product: USB 10/100 LAN
[ 471.510360] usb 1-1.1: Manufacturer: Realtek
[ 471.510364] usb 1-1.1: SerialNumber: 00E04C3607A9
[ 471.701309] usb 1-1.1: reset high-speed USB device number 4 using xhci-hcd
[ 471.882926] r8152 1-1.1:1.0 eth1: v1.09.9可以发现，多出了一行识别信息，r8152被识别为eth1（此时ifconfig发现新的网卡，但是没有IP等信息），使用udhcpc命令为eth1分配动态ip地址：
udhcpc -i eth1ifconfig查看网络配置情况：
root@MyDevice:~# ifconfig
eth0 Link encap:Ethernet HWaddr 00:0D:0D:D6:B6:21
inet6 addr: fe80::20d:dff:fed6:b621/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:367 errors:0 dropped:0 overruns:0 frame:0
TX packets:525 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:92887 (90.7 KiB) TX bytes:74001 (72.2 KiB)
Interrupt:30
eth0.10 Link encap:Ethernet HWaddr 00:0D:0D:D6:B6:21
inet addr:10.16.7.122 Bcast:10.16.7.255 Mask:255.255.255.0
inet6 addr: 2001:10:16:8::60/64 Scope:Global
inet6 addr: fe80::20d:dff:fed6:b621/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:97 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:0 (0.0 B) TX bytes:18767 (18.3 KiB)
eth1 Link encap:Ethernet HWaddr 00:E0:4C:36:07:A9
inet addr:192.168.1.101 Bcast:192.168.1.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:20 errors:0 dropped:0 overruns:0 frame:0
TX packets:13 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:4679 (4.5 KiB) TX bytes:2086 (2.0 KiB)
lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
inet6 addr: ::1/128 Scope:Host
UP LOOPBACK RUNNING MTU:65536 Metric:1
RX packets:201 errors:0 dropped:0 overruns:0 frame:0
TX packets:201 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:22516 (21.9 KiB) TX bytes:22516 (21.9 KiB发现eth1的IP地址生效，且与eth0.30在同一局域网，接着验证eth1的网络性能，发现无法ping通局域网中的其他设备。
route add default gw 192.168.1.1 eth1进一步设置eth1的默认网关，再ping成功。t802:~# route add default gw 192.168.1.1 eth1