How to read/write a multi-layer image from a Photoshop format plugin?

Hello,

I wrote a Photoshop plugin that can load and save a new in-house file format. Now, I would like to be able to load/save images with multiple layers. I am not sure how to feed the layers to photoshop when I load the file.

I tried to set

     gFormatRecord->layerData = 2;

in the DoReadStart() routine but Photoshop never called    formatSelectorReadLayerStart    to load the additional layers.

Now, I have a vague idea that I may have to do something in the PiPL resource file to enable layer support. However, this is not very well documented.

Question 1:  What I should do to enable layers (if I have to do anything) ?

Question 2:  Do I need a Photoshop version >= 10 to support multi layer plugins ? In the doc it says:

Question 3: when everything goes well, will Photoshop request the leayers via a mechanism simialar to what it does when loading the main image (readPrepare() readStart(), readContinue() ....  except that it will be   ReadLayerstart(), .....)  ?

Thanks!!

Gilbert