Android 4.4 Kitkat 使能 USB adb 功能

    When building your kernel, make sure to configure in FunctionFS:
 
     Device Drivers -> USB Support -> USB Gadget Support
 
         -> USB Gadget Driver -> Function Filesystem  

    Modify your boot parameters to set the vendor and product ids so adb on your host recognizes the device.
 
     g_ffs.idVendor=0x18d1 g_ffs.idProduct=0x4e26
 
 
    Alternatively this can also be done if you built the gadget driver as a module at load time:
 

    insmod g_ffs.ko idVendor=0x18d1 idProduct=0x4e26

    Now here I’m assuming you’ve got a serial port working. Boot your target device with your new kernel (and insmod the g_ffs driver if necessary), and setup the functionfs directory:

    # mkdir /dev/usb-ffs
    # mkdir /dev/usb-ffs/adb
    # mount -o uid=2000,gid=2000 -t functionfs adb /dev/usb-ffs/adb

    If everything is working, you can kill adbd and when it restarts it should find the functionfs mount and make use of it.
 

    # ps adbd
    # kill <pid for adbd>

 On your host system, connect to the target using the adb program:

    $ ./adb shell
    root@android:/#

     Hooray there’s your shell!