升级我的华为电话（rooted）到Android 5.1.1（cm 12.1）"USB调试" 选项呈现出邮件：
禁用开发人员模式并再次启用 禁用开发人员模式，重新启动手机并再次启用它 卸下电缆并尝试所有上述解决方案
After upgrading my Huawei phone (which is rooted) to Android 5.1.1 (CM 12.1) the 'USB debugging' option is greyed out with message:
'Device is in charging mode, USB debugging is disabled'.
The message is present even when the cable is not connected.
I have already tried following solutions (but the USB debugging is still greyed out):
Restarting the phone
Disabling developer mode and enabling again
Disabling developer mode, restarting the phone and enabling it again
Removing the cable and trying all above solutions
Removing 'persist.system.usb.config' file from data/property/ folder and restarting the device solved the issue for me.
After restart, the device shows the option to enable 'USB debugging'.
Root access is required to remove that file.
Screenshots (click images for larger variants)
Plug out your USB cable and go to the developer options of your device. There you can activate USB debugging and then you can plug your cable back in. It isn't enough to only activate developer options.