question about probe_roms

Hi:
I'm reading linux kernel 2.4 source code and puzzled with
probe_roms().
In this function , rom was probed and request_resource was called. but I don't understand these codes:

     for (base = 0xC0000; base < 0xE0000; base+=2048) {
         romstart = bus_to_virt(base);
         if (!romsignature(romstart))
                 continue;
         request_resource(&iomem_resource, rom_resources+roms);
         roms++;
         break;
     }

Because whether video rom is start from 0xC000:0000 or not, we request a memory
resource start at 0xC0000 (I don't find any code change the contents of rom_resources)
So I think these codes assume that there is a video rom at 0xc0000, but if this is true,
why not request_resource as SystemRom?

Thank you in advance.

Best regards !

-- jason --