82557 PCI BAR0 BAR1 BAR2 inconsistencies..?

Hello,

since i don't have programmer's refrence manual for eepro100 
82557
card i have no idea about my query below.

.in 82557 PCI card it has resource requirement by BAR0 BAR1 and 
BAR2.
BAR0 and BAR2 are PCI mem type while BAR1 is PCI io type.

till now whenever i have ported  linux driver i always have used 
only BAR1 that is a PCI IO type.
to the best of my remembrance even if don't initialise the BAR0 
and
BAR2 in PCI bios it worked fine.

my query is ..

1.why there has been BAR1 and BAR2 requirement provisioned ..is 
it
for any future extension ?

2.can i get card working without BAR1 ( PCI IO) 
initialisation..?

i am further confused as in my MIPS source tree i observe the 
eepro100
driver doing,

IOADDR = request_mem_region(for PCI BAR0 resource)
IOADDR= ioremap(IOADDR , length of PCI BAR0 resource)

then uses this IOADDR everywhere.

here it only uses BAR0 resource.

pls. help me.

PLS.CC TO ME AS I AMN'T YET SUBSCRIBED.....

Best Regards,
Ashish