From Android ICS onwards, MTP mode is the default USB connection mode. To enable the mass storage mode in R13.5,
1. Change the persist.sys.usb.config property from "mtp" to "mass_storage" to enable the mass storage function by default.
2. In storage_list.xml, turn on the "android:allowMassStorage" flag for the mounted volume so that it can be shared for ums. Please note that there are several storage_list.xml under the "device/fsl" folder for different board configurations. Be careful you are editing the appropriate one.
The above change for i.MX6SL is summarized in this patch.
Because your PC may register your board as a MTP device, you may need to update the device driver to make the mass storage device effective.
To turn on the USB storage after USB connection, please click the small USB icon on the status bar at the bottom of screen. A pop up menu will be shown. Then choose "Turn on USB storage".
For further information, please refer to External Storage Technical Information | Android Developers.
Original Attachment has been moved to: R13.5_usb_mass_storage.patch.zip