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BUS_ALLOC_RESOURCE(9)  FreeBSD Kernel Developer's Manual BUS_ALLOC_RESOURCE(9)

     bus_alloc_resource, bus_alloc_resource_any, bus_alloc_resource_anywhere
     --	allocate resources from	a parent bus

     #include <sys/param.h>
     #include <sys/bus.h>

     #include <machine/bus.h>
     #include <sys/rman.h>
     #include <machine/resource.h>

     struct resource *
     bus_alloc_resource(device_t dev, int type,	int *rid, rman_res_t start,
	 rman_res_t end, rman_res_t count, u_int flags);

     struct resource *
     bus_alloc_resource_any(device_t dev, int type, int	*rid, u_int flags);

     struct resource *
     bus_alloc_resource_anywhere(device_t dev, int type, int *rid,
	 rman_res_t 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 gener-
     ally should be called in attach, but (except in some rare cases) never

     The bus_alloc_resource_any() and bus_alloc_resource_anywhere() functions
     are convenience wrappers for bus_alloc_resource().
     bus_alloc_resource_any() sets start, end, and count to the	default	re-
     source (see description of	start below).  bus_alloc_resource_anywhere()
     sets start	and end	to the default resource	and uses the provided count

     The arguments are as follows:

     dev is the	device that requests ownership of the resource.	 Before	allo-
     cation, the resource is owned by the parent bus.

     type is the type of resource you want to allocate.	 It is one of:

     PCI_RES_BUS     for PCI bus numbers

     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, this is an	index into the array of	resources de-
     scribed 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.

     start and end are the start/end addresses of the resource.	 If you	spec-
     ify 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

     RF_ALLOCATED  resource has	been reserved.	The resource still needs to be
		   activated with bus_activate_resource(9).

     RF_ACTIVE	   activate resource atomically.

		   resource is prefetchable.

     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, pccard(4) can-
		   not share IRQs while	cardbus(4) can.

     RF_UNMAPPED   do not establish implicit mapping when activated via

     A pointer to struct resource is returned on success, a null pointer oth-

     This is some example code that allocates a	32 byte	I/O port range and an
     IRQ.  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_any(dev, SYS_RES_IRQ, &irqid,

     bus_activate_resource(9), bus_adjust_resource(9), bus_map_resource(9),
     bus_release_resource(9), device(9), driver(9)

     This manual page was written by Alexander Langer <>
     with parts	by Warner Losh <>.

FreeBSD	13.0			 May 20, 2016			  FreeBSD 13.0


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