I have recently received my Pi2 and have successfully been using it on my lapdock100. As per instructions on other posts I had to modify the config.txt file and now with a boot sequence i can get the lapdock 100 screen displaying 100% of the time. It can take a bit of time getting used to but considering the lapdock is supposed to get the correct signals from a phone, i am prepared to put up with a slight bit of hassle to get it working.
The boot sequence is as follows:
Pre setup - Make sure the lapdock is fully charged and that you have both the HDMI and USB cables plug into the lapdocks connector and the lapdock screen is in the 'open' position. Nothing is plugged into the Pi2
1. Plug the HDMI connector into the Pi2, and pay attention to the 'power on' led on the lapdock. As you plug the connector into the Pi2, this led will quickly flash. (Lapdock is in a temporary power on state)
2. Once you have seen the power led quickly flash on the lapdock, remove the HDMI connector from the Pi2 but still pay close attention to the power led on the lapdock. After approx 30-40 seconds, this will flash again. This indicates that the lapdock has powered down.
3. Now plug in the HDMI connector again and you should see the screen on the lapdock activate. This where you need to be quick because as soon as you see the lapdock screen activate, you need to plug in the micro usb connector into the Pi2's power port. If you delay plugging in the Pi2's power connector, the lapdock thinks nothing is connected and will power off the LCD. If this happens, you need to start all over again from Pre-setup
4. If you have timed it correctly and plugged the Pi2's power connector in as soon as you saw the lapdock's screen activate, you will see the Pi2 booting into it's operating system. At this point while you see the Pi2 booting, plug in the other USB cable into the Pi2 so that the lapdocks keyboard and touchpad will function.
A couple of things to note. If at any time you power down the Pi2 and remove any of the cables, you must start from Pre-setup to be able to get the lapdock display to work properly. If you try to cut corners it just will not work. I've spent over 4hrs trying all sorts of different combinations in the hope the lapdock would quickly display again once i've powered down the Pi2 and removed it's cables but the only method that worked reliably and 100% was the method i've just described.
If you plan on leaving the Pi2 connected to the lapdock to return to it latter, just shutdown the Pi2 either by command line or via x windows, which ever one you happen to be in at the time BUT make sure you leave all the cables connected. Once you shutdown the Pi2 you will notice the LCD screen display goes off but the Pi2 is still powered on (Pi2 power led still on). Wait till the lapdock turns off it's power, you will know this by focusing on the lapdocks power on led. After approx 30-40 seconds of you telling the Pi2 to shutdown, the lapdock will power down. As soon as you see that led flash again to indicate the lapdock has powered down and provided you have not removed ANY cables from either the lapdock or Pi2, pressing the lapdocks power button will power on everything properly. You will notice the LCD activate and then the Pi2 booting instructions scrolling down the screen.
Like others I was frustrated at how long and cumbersome it took to try and get not only the Pi but also the Pi2 to reliably function with the lapdock 100 and now i can confidently say I have and i am pleased with the results. As long as I follow the procedure I've laid out, all i am basically doing is waiting 40 seconds each time for the lapdock to power down. That's a small inconvenience I am prepared to take