adb 开关
启动是在rc文件中
./out/target/product/xxxx/root/init.usb.rc
# adb only USB configuration
# This is the fallback configuration if the
# USB manager fails to set a standard configuration
on property:sys.usb.config=adb && property:sys.usb.configfs=0
write /sys/class/android_usb/android0/enable 0
write /sys/class/android_usb/android0/idVendor 18d1
write /sys/class/android_usb/android0/idProduct 4EE7
write /sys/class/android_usb/android0/functions ${sys.usb.config}
write /sys/class/android_usb/android0/enable 1
start adbd
setprop sys.usb.state ${sys.usb.config}
则sys.usb.config=adb
属性默认值在系统编译时生成的default.prop
./device/mediatek/mt6580/device.mk
ifeq ($(TARGET_BUILD_VARIANT),user)
PRODUCT_DEFAULT_PROPERTY_OVERRIDES += persist.sys.usb.config=mtp
else
PRODUCT_DEFAULT_PROPERTY_OVERRIDES += persist.sys.usb.config=adb
endif
则user版本为mtp不打开adb,其他版本为adb,打开 adb