bus_alloc_resource -- alloc resources on a bus
struct resource *
bus_alloc_resource(device_t dev, int type, int *rid, u_long start,
u_long end, u_long count, u_int flags);
This is an easy interface to the resource-management functions. It hides
the indirection through the parent's method table. This function generally
should be called in attach, but (except in some rare cases) never
Its arguments are as follows:
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:
SYS_RES_IRQ for IRQs
SYS_RES_DRQ for ISA DMA lines
SYS_RES_IOPORT for I/O ports
SYS_RES_MEMORY 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 0 for start and ~0 for end and 1 for count, the default
values for the bus are calculated.
count is the size of the resource, e.g. the size of an I/O port (often 1,
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 as the
flags sets the flags for the resource. You can set one or more of these
RF_ALLOCATED resource has been reserved. The resource still needs to be
activated with bus_activate_resource(9).
RF_ACTIVE activate resource atomically.
RF_SHAREABLE resource permits contemporaneous sharing. Should always be
set unless you know, that the resource cannot be shared.
It is the bus-code's task to filter out the flag if the bus
doesn't support sharing, which is, for example, the case
for pccard/cardbus, which can or cannot share devices,
depending on the bus.
RF_TIMESHARE resource permits time-division sharing.
A pointer to struct res is returned on success, a null pointer otherwise.
This is some example code. The values of portid and irqid should be
saved in the softc of the device after these calls.
struct resource *portres, irqres;
int portid, irqid;
portid = 0;
irqid = 0;
portres = bus_alloc_resource(dev, SYS_RES_IOPORT, &portid,
0ul, ~0ul, 32, RF_ACTIVE);
irqres = bus_alloc_resource(dev, SYS_RES_IRQ, &irqid,
0ul, ~0ul, 1, RF_ACTIVE | RF_SHAREABLE);
bus_activate_resource(9), bus_release_resource(9), device(9), driver(9)
This man page was written by Alexander Langer <email@example.com> with
parts by Warner Losh <imp@FreeBSD.org>.
FreeBSD 5.2.1 May 18, 2000 FreeBSD 5.2.1 [ Back ]