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     bus_alloc_resource, bus_alloc_resource_any — 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, u_long start, u_long end, u_long count,
         u_int flags);

     struct resource *
     bus_alloc_resource_any(device_t dev, int type, int *rid, 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 earlier.

     The bus_alloc_resource_any() function is a convenience wrapper for bus_alloc_resource().  It
     sets the values for start, end, and count to the default resource (see description of start

     The 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, 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

     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:

     RF_ALLOCATED  resource has been reserved.  The resource still needs to be activated with

     RF_ACTIVE     activate resource atomically.

     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) cannot share IRQs while cardbus(4) can.

     RF_TIMESHARE  resource permits time-division sharing.


     A pointer to struct resource is returned on success, a null pointer otherwise.


     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,
                             RF_ACTIVE | RF_SHAREABLE);


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


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