[Shield Android TV Android Development] whiteak:
Alright guys, here is a quick rundown of how I have gained Full Root Access for firmware version 7.2.2 for the 2017 Darcy Model. Can also confirm it works for 7.2.1 as well. Should also work for 7.2.0, I cannot confirm this as I have not actually tried but I have successfully done it with 7.2.2 and 7.2.1. The majority of you would probably be on 7.2.1, but there is a way to get a test version of 7.2.2 from Nvidia from their forums. But doesn't matter, instructions and files are the same regardless of what ever firmware version you are on whether it be 7.2.2 or 7.2.1.

Credit must be given to Zulu99 as it is his modified dtb file that makes this all possible. He has his own custom Firmware and he is the one who made this modified dtb file to be able to get us up and running again. Now I haven't tried his firmware, so I cannot comment on how it works, but I am using his dtb file to help us continue using the Nvidia Stock Firmware with Full Root Access again, so I must give thanks and credit to Zulu99. For anyone interested in his work you can check his page out at http://www.videomap.it/forum/viewtopic.php?f=25&t=1965. Take note, the instructions I am about to give are not for his Firmware, they are how to use Nvidia Stock Firmware and gain Full Root access, 2 totally different Firmwares, just want to make that clear.

I am a bit short for time, so I will just give a brief rundown of what to do. Downunder35m may or may not decide to make a better guide, totally up to him. I am going to presume most of you already have a good idea on what I am talking about, so there should be no real issues following my brief instructions. When needed, I installed apks via adb just fyi, if you don't know how to do that, then please do not proceed any further, this guide is not for you.

Files needed:

Kantjer Patched boot.img: https://mega.nz/#!H59GiIyb!_zsoqaIdwG1PQj2VNKra82hWORWfjCs45F1LHYV-1jE

Kantjer Magisk Manager: https://mega.nz/#!y4t0xapD!uoCt1Z85hNbnsXDTi4TAjkh2JY8yIgV49aIH_Er6pvE

Zulu99 dtb file: https://mega.nz/#!ih8Q0CgZ!JctOaSURx2-Xo7ceuhdCyN57rmrnFbpX2PtzmtPTF7E

I patched the latest version of Kantjers Magisk (Can use Official, I just like Kantjers) to the stock 7.2.1 or 7.2.2 boot.img (certain they are the same anyway). I downloaded Zulu99's dtb file and then I basically just got to a Clean install of 7.2.1. or 7.2.2 depending on what you have.

Booted to Fastboot and just did this:

fastboot flash boot patched_boot.img

fastboot flash dtb tegra210-darcy-p2894-0050-a04-00.dtb

fastboot -w

fastboot reboot

Booted to System.

Let it sit for a bit, now not too sure if this is normal or not, but it appeared to lock up a bit and sometimes go to a Black Screen and seem unresponsive, I just let it sit for 5-10 mins and it rebooted on it's own accord and booted to system, now it was normal (responsive, no black screens etc). I was kind of worried about why it was unresponsive and going to a black screen, so I did another Factory Reset even though it appeared I didn't need to after the restart, I did anyway, it booted to System fine, this time with no sign of unresponsiveness or black screens. Let it sit for 5 mins anyway, all good.

Uninstalled the half pre-installed version of Magisk Manager installed from flashing the patched boot.img. Installed the Full Version of Kantjers latest Magisk Manager, opened, asks to complete Setup, click allow, asks again to complete setup, again click allow, Magisk Manager is now installed.

Tested for Full Root Access, Uninstalls and deletes System Apps and System Folders.

Success. Stock 7.2.1 or 7.2.2 with Full Root Access.

Now it is to be said, that I also done this to a Second Shield I have and at the end I also got the unresponsiveness etc, I also done a Factory Reset and the unresponsiveness was still there unlike the First Shield I flashed when the unresponsiveness dissapeared after a Factory Reset. On the second shield all I did was a Restart and upon restart everything was normal again. Not too sure what really causes it, but a restart fixes it.

**Take note*** You do not need to use my Kantjer Patched Boot.img and Manager, you could use the official ones, I just use Kantjers, so that is what is provided in instructions.