tail head cat sleep
QR code linking to this page

Manual Pages  — BUS_MAP_RESOURCE


bus_map_resource – map or unmap an active resource



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

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

bus_map_resource(device_t dev, int type, struct resource *r, struct resource_map_request *args, struct resource_map *map);

bus_unmap_resource(device_t dev, int type, struct resource *r, struct resource_map *map);

resource_init_map_request(struct resource_map_request *args);


These functions create or destroy a mapping of a previously activated resource. Mappings permit CPU access to the resource via the bus_space(9) API.

The arguments are as follows:
  The device that owns the resource.
  The type of resource to map. It is one of:

  for I/O ports
  for I/O memory
  A pointer to the struct resource returned by bus_alloc_resource(9).
  A set of optional properties to apply when creating a mapping. This argument can be set to NULL to request a mapping of the entire resource with the default properties.
  The resource mapping to create or destroy.

Resource Mappings

Resource mappings are described by a struct resource_map object. This structure contains a bus_space(9) tag and handle in the r_bustag and r_bushandle members that can be used for CPU access to the mapping. The structure also contains a r_vaddr member which contains the virtual address of the mapping if one exists.

The wrapper API for struct resource objects described in bus_activate_resource(9) can also be used with struct resource_map. For example, a pointer to a mapping object can be passed as the first argument to bus_read_4(). This wrapper API is preferred over using the r_bustag and r_bushandle members directly.

Optional Mapping Properties

The struct resource_map_request object passed in args can be used to specify optional properties of a mapping. The structure must be initialized by invoking resource_init_map_request(). Properties are then specified by setting one or more of these members:
offset, length
  These two members specify a region of the resource to map. By default a mapping is created for the entire resource. The offset is relative to the start of the resource.
  Specifies a memory attribute to use when mapping the resource. By default memory mappings use the VM_MEMATTR_UNCACHEABLE attribute.


Zero is returned on success, otherwise an error is returned.


This maps a PCI memory BAR with the write-combining memory attribute and reads the first 32-bit word:
        struct resource *r;
        struct resource_map map;
        struct resource_map_request req;
        uint32_t val;
        int rid;

        rid = PCIR_BAR(0);         r = bus_alloc_resource_any(dev, SYS_RES_MEMORY, &rid, RF_ACTIVE |          RF_UNMAPPED);         resource_init_map_request(&req);         req.memattr = VM_MEMATTR_WRITE_COMBINING;         bus_map_resource(dev, SYS_RES_MEMORY, r, &req, &map);         val = bus_read_4(&map, 0);


bus_activate_resource(9), bus_alloc_resource(9), bus_space(9), device(9), driver(9)


This manual page was written by John Baldwin <Mt jhb@FreeBSD.org>.

BUS_MAP_RESOURCE (9) February 5, 2018

tail head cat sleep
QR code linking to this page

Please direct any comments about this manual page service to Ben Bullock. Privacy policy.