What is the ioremap() function?

I have some question about ioremap() function...

In arch/ppc/mm/init.c file, there is ioremap() function..
What is the main functionality of ioremap()?

It takes two argument...
I must use ioremap() for flash device..

I think first argument is physical address of memory mapped device, so I put that argument physical starting address of flash device. In my case, starting address of flash is 0XE4000000. and I use 4MB flash.
Am I use virtual address for first argument?

So I called ioremap() function with following line.

ioremap(0xE4000000, 1024*1024*4);
Am I correct?

Please answer my question...


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