Best way to support mulitple planes?

[Timur Tabi <timur@freescale.com>]

Hi, I'm new to the framebuffer subsystem, so forgive me if this is a FAQ. 
I've spent the past couple hours scouring web sites and sample code, but I 
don't have a definitive answer to my question.

I have a device that supports three planes - memory areas that the hardware 
reads from to generate the physical image.  Each plane supports an alpha 
channel for each pixel, and the hardware just blends all three planes together 
when it draws the image.

Currently, our driver create three framebuffer devices, /dev/fb0, /dev/fb1, 
and /dev/fb2, which means three calls to register_framebuffer().  Is this the 
correct way to do it?

The reason I ask is that our hardware can only handle three planes if the 
resolution is 1024x768 or below.  I can't figure out any way of telling the 
framebuffer subsystem that if it switches to 1280x1024 in plane 0, that plane 
1 and 2 no longer exist.  Any suggestions on how to handle that?

-- 
Timur Tabi
Linux Kernel Developer @ Freescale

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