GrahicsClient Initialization

[Chandrasekhar]

Hi,
I am a newbie to the Linux kernel Programming.I was browsing through the
arch/arm/mach-sa1100/graphicsclient.c file.Can you answer the following
questions.
What is the purpose of the function iotable_init ?
What is the purpose of the map_desc structure and what is the significance
of all the fields in this structure ?
Is the initialization of this structure necessary ?
and finally what is the entry point i.e which function is called first for
the GraphicsClient initialization ?

Thanks and Regards

Chandrasekhar