Man page 9 : pci_bus_alloc_resource

pci_bus_alloc_resource - allocate a resource from a parent bus

int pci_bus_alloc_resource(struct pci_bus *  bus , struct resource *  res , resource_size_t  size , resource_size_t  align , resource_size_t  min , unsigned int  type_mask , resource_size_t (* alignf ) (void *, const struct resource *, resource_size_t, resource_size_t), void *  alignf_data );

bus
    PCI bus

res
    resource to allocate

size
    size of resource to allocate

align
    alignment of resource to allocate

min
    minimum /proc/iomem address to allocate

type_mask
    IORESOURCE_* type flags

alignf
    resource alignment function

alignf_data
    data argument for resource alignment function

Given the PCI bus a device resides on, the size, minimum address, alignment and type, try to find an acceptable resource allocation for a specific device resource.