dev is the device that requests ownership of the resource. Before allocation, the resource is owned by the parent bus.
type is the type of resource you want to allocate. It is one of:
for ISA DMA lines
for I/O ports
for I/O memory
rid points to a bus specific handle that identifies the resource being allocated. For ISA this is an index into an array of resources that have been setup for this device by either the PnP mechanism, or via the hints mechanism. For PCCARD, similar things are used as of writing, but that may change in the future with newcard. For PCI it just happens to be the offset into pci config space which has a word that describes the resource. The bus methods are free to change the RIDs that they are given as a parameter. You must not depend on the value you gave it earlier.
start and end are the start/end addresses of the resource. If you specify values of 0ul for start and ~0ul for end and 1 for count, the default values for the bus are calculated.
count is the size of the resource. For example, the size of an I/O port is usually 1 byte (but some devices override this). If you specified the default values for start and end, then the default value of the bus is used if count is smaller than the default value and count is used, if it is bigger than the default value.
flags sets the flags for the resource. You can set one or more of these flags:
resource has been reserved. The resource still needs to be activated with bus_activate_resource(9).
activate resource atomically.
resource permits contemporaneous sharing. It should always be set unless you know that the resource cannot be shared. It is the bus drivers task to filter out the flag if the bus does not support sharing. For example, pccard(4) cannot share IRQs while cardbus(4) can.