What protocols are involved in the modes of USB connection from an Android phone to a computer?

Question

When I link a phone (HarmonyOS 2.0.0, Honor 10) to a Linux laptop, the phone pops up the following options:

When I link a phone (Android 12, Moto G Pure) to a Linux laptop, the phone pops up the following options:

I was wondering what protocol (e.g. MTP, PTP) is involved in each option for the two phones?

Is MTP enabled by file transfer, or photo (& video) transfer?

What is the protocol involved in the previous "USB Massive Storage" mode?

Photo and video transfer should be PTP. USB mass storage mode isn't supported by Android anymore. In that mode the whole sdcard partition was dismounted on the phone and instead connected as emulated USB stick to the PC. At that time the sdcard partition was therefore formatted FAT32. AFAIR this mode was abandoned in Android 3 or 4 and instead we now have the "emulated" sdcard folder. — Robert, Commented Jul 3 at 21:25

Naira Nicol · Accepted Answer · 2024-07-04 13:16:42Z

HarmonyOS 2.0.0

Photo & Video Transfer: This lets user to move photos and videos between to phone & computer using Picture Transfer Protocol.
File Transfer: Allow user to transfer any type of files using Media Transfer Protocol.
Charge Only: It's only for charging phones but need be aware before plug-in to unkown device.
Reverse Charge: Lets phone charge another device through the USB connection.
Input MIDI: Used for connecting musical instruments or MIDI devices.

Note - It's same for android 12

Like a USB stick directly on your computer. It's been replaced by MTP, which is more flexible and make phone to be used normally while connected

MTP: Used for transferring files between devices.
PTP: Used for transferring photos and videos between devices.
USB Mass Storage: Old method that directly exposed phone storage as a USB drive. Not commonly used anymore.

Mostly in modern phones used MTP for file transfers because it works well with different computers and operating systems.