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BUS_MAP_RESOURCE(9) Kernel Developer's Manual BUS_MAP_RESOURCE(9)

bus_map_resource, bus_unmap_resource, resource_init_map_request — 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>

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

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

void
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:

dev
The device that owns the resource.
type
The type of resource to map. It is one of:

for I/O ports
for I/O memory
r
A pointer to the struct resource returned by bus_alloc_resource(9).
args
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.
map
The resource mapping to create or destroy.

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 (). This wrapper API is preferred over using the r_bustag and r_bushandle members directly.

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 (). 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.
memattr
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 <jhb@FreeBSD.org>.

February 5, 2018 Debian