背景

在 Linux-3.8 以後，Android 的內核分支，便去掉了 f_adb，改使用 USB function FS，在用戶空間實現 USB adb 功能。這篇文章根據原作者的 Google+ 文章，在 Atmel sama5 開發板上做了測試，將步驟記錄如下，供需要使用的讀者參考，你也可以查看作者原文：https://plus.google.com/111524780435806926688/posts/AaEccFjKNHE

在 Linux-3.10 上使能 USB ADB

編譯內核時使能 USB FunctionFS

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

設置正確的 USB vendor ID 和 Product ID

這個設置可以放在 bootcmd 或者加載內核模塊的時候通過參數傳遞： 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

啟動 Android 並掛載 functionFS， 使能 USB adb

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

重啟 adbd 守護進程

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 

然後進入 cmd 或者 Linux Host 就可以成功連接 usb adb 獲得 Android shell 了

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

    $ ./adb shell
    root@android:/#

Hooray there's your shell!