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.Dd May 20, 2016
.Dt BUS_ALLOC_RESOURCE 9
.Os
.Sh NAME
.Nm bus_alloc_resource ,
.Nm bus_alloc_resource_any ,
.Nm bus_alloc_resource_anywhere
.Nd allocate resources from a parent bus
.Sh SYNOPSIS
.In sys/param.h
.In sys/bus.h
.Pp
.In machine/bus.h
.In sys/rman.h
.In machine/resource.h
.Ft struct resource *
.Fo bus_alloc_resource
.Fa "device_t dev" "int type" "int *rid" "rman_res_t start" "rman_res_t end"
.Fa "rman_res_t count" "u_int flags"
.Fc
.Ft struct resource *
.Fn bus_alloc_resource_any "device_t dev" "int type" "int *rid" "u_int flags"
.Ft struct resource *
.Fo bus_alloc_resource_anywhere
.Fa "device_t dev" "int type" "int *rid" "rman_res_t count" "u_int flags"
.Fc
.Sh DESCRIPTION
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 earlier.
.Pp
The
.Fn bus_alloc_resource_any
and
.Fn bus_alloc_resource_anywhere
functions are convenience wrappers for
.Fn bus_alloc_resource .
.Fn bus_alloc_resource_any
sets
.Fa start ,
.Fa end ,
and
.Fa count
to the default resource (see description of
.Fa start
below).
.Fn bus_alloc_resource_anywhere
sets
.Fa start
and
.Fa end
to the default resource and uses the provided
.Fa count
argument.
.Pp
The arguments are as follows:
.Bl -item
.It
.Fa dev
is the device that requests ownership of the resource.
Before allocation, the resource is owned by the parent bus.
.It
.Fa type
is the type of resource you want to allocate.
It is one of:
.Bl -tag -width SYS_RES_MEMORY
.It Dv PCI_RES_BUS
for PCI bus numbers
.It Dv SYS_RES_IRQ
for IRQs
.It Dv SYS_RES_DRQ
for ISA DMA lines
.It Dv SYS_RES_IOPORT
for I/O ports
.It Dv SYS_RES_MEMORY
for I/O memory
.El
.It
.Fa 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, this is an index into the array of resources described by the PC Card's
CIS entry.
For PCI, the offset into PCI config space which has the BAR to use to access
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.
.It
.Fa start
and
.Fa end
are the start/end addresses of the resource.
If you specify values of 0ul for
.Fa start
and ~0ul for
.Fa end
and 1 for
.Fa count ,
the default values for the bus are calculated.
.It
.Fa 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
.Fa start
and
.Fa end ,
then the default value of the bus is used if
.Fa count
is smaller than the default value and
.Fa count
is used, if it is bigger than the default value.
.It
.Fa flags
sets the flags for the resource.
You can set one or more of these flags:
.Bl -tag -width RF_SHAREABLE
.It Dv RF_ALLOCATED
resource has been reserved.
The resource still needs to be activated with
.Xr bus_activate_resource 9 .
.It Dv RF_ACTIVE
activate resource atomically.
.It Dv RF_PREFETCHABLE
resource is prefetchable.
.It Dv RF_SHAREABLE
resource permits contemporaneous sharing.
It should always be set unless you know that the resource cannot be shared.
It is the bus driver's task to filter out the flag if the bus does not
support sharing.
For example,
.Xr pccard 4
cannot share IRQs while
.Xr cardbus 4
can.
.It Dv RF_UNMAPPED
do not establish implicit mapping when activated via
.Xr bus_activate_resource 9 .
.El
.El
.Sh RETURN VALUES
A pointer to
.Va struct resource
is returned on success, a null pointer otherwise.
.Sh EXAMPLES
This is some example code that allocates a 32 byte I/O port range and an IRQ.
The values of
.Va portid
and
.Va irqid
should be saved in the softc of the device after these calls.
.Bd -literal
	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_any(dev, SYS_RES_IRQ, &irqid,
			RF_ACTIVE | RF_SHAREABLE);
.Ed
.Sh SEE ALSO
.Xr bus_activate_resource 9 ,
.Xr bus_adjust_resource 9 ,
.Xr bus_map_resource 9 ,
.Xr bus_release_resource 9 ,
.Xr device 9 ,
.Xr driver 9
.Sh AUTHORS
.An -nosplit
This manual page was written by
.An Alexander Langer Aq Mt alex@big.endian.de
with parts by
.An Warner Losh Aq Mt imp@FreeBSD.org .