[Q] USB Masst Storage ? UMS ...

The phone doesn't offer UMS. Be disappointed all you want, it's not going to happen mate.

Hello. I have a semi good news.

My view of the world changed tonight.

I received a message from andreasyeah telling me to try https://play.google.com/store/apps/details?id=com.softwarebakery.drivedroid&hl=en ... and it's amazing. He also recommends to use ElementalX kernel.

First, what UMS was for me untill yesterday ? Use my phone as SD to USB card adapter, and, make my PC able to read and write on SD, as if SD was in a legacy USB card reader. Plug phone, android unmounts sd, and pushes SD to USB, and PC can mount the SD, and do whatever it wants to it.

Whatever used to include .. repartition, reformat, and, some some of my friends like Galoula ... install a MBR on SD, so that, when any PC is broken, he can boot the PC by just plugging the phone. His phone became a classic external disk. Android could partly read the SD, with limitations (legacy android can only read first partition in FAT; having fat on non first part, and, reading non FAT partitions requires ... manual operations).

This app does things a completely differen way. To make the story short ... it downloads an ISO over internen, store it in your phone (at any place you like, any folder), and, presents this ISO as a USB-CD. Emulates the USB-CD, and provides the media inside. App let you choose amongst large choice of distributions, install CD, and live CDs. The last option is to ask the app to create an empty drive, and, eventually, format it in FAT.

Negs:
- phone is no more a SD adapter
- copying files from phone to PC requires to manually mount the FAT block, copy, unmount; then, the app will show it as a CD
- copying from PC to phone requires a CD burning soft, and will erease the whole block
- the process can fail at many places. Phone can fail to emulate the CD. PC can fail to detect it. But, in most case, PC will fail to see partitions inside the CD. Also, for me, boot failed on two computers (BIOS could see the USB CD drive, but boot failed without reason)
- apps only emulates a CD; so, in short, the volume is READ ONLY. Except for CDRW softs.

Advantages:
- can work for phones that do not have SD slot
- can store as many boot sections as you want.
- include a large pannel of distributions, live CD, and other similar stuff
- provides partial workaround for people like us who are limited to MTP by default.
- UMS independant from SD
- images can be stored at any place in the phone (or even over network for me ^^ my phone mounts NFS, Samba, CIFS, SSHFS ... )

Apps has good design, and offers a variety of UMS implementations, and a blacklist for phones known to not work.

Success is heavily ROM and kernel dependant.

So, depending on the reasons why you want UMS ... this could be an alternative. Or not

I am going to test related apps over night; first needed to make my report for this one.

Here is a quick tuto from a friend:

echo 0 > /sys/class/android_usb/android0/enable
echo 22D9 > /sys/class/android_usb/android0/idVendor
echo 2767 > /sys/class/android_usb/android0/idProduct
echo adb,mass_storage > /sys/class/android_usb/android0/functions
echo /storage/sdcard1/debian.iso > /sys/devices/virtual/android_usb/android0/f_mass_storage/lun/file
echo 1 > /sys/class/android_usb/android0/enable

Here is the interesting part:
root@htc_m8:/storage/emulated/legacy # cat /sys/class/android_usb/android0/functions
mtp,adb,mass_storage

This means ... my kernel can do UMS. I will dig this later.

Sounds like this method can be used to simulate several devices at the same time: several HDD, several CDs ...

Not sure if you're still trying to figure this out, but I got UMS working in TWRP . Link is in my sig.