bus_map_resource9
Map or unmap an active resource
Usage
#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, struct resource *r, struct resource_map_request *args, struct resource_map *map);
int
bus_unmap_resource(device_t dev, struct resource *r, struct resource_map *map);
void
resource_init_map_request(struct resource_map_request *args);
Overview
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.
- 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
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.
- memattr
-
Specifies a memory attribute to use when mapping the resource. By default memory mappings use the VM_MEMATTR_UNCACHEABLE attribute.
Return values
Zero is returned on success, otherwise an error is returned.
Examples
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);
Releases
25 releases since FreeBSD 11.0-RELEASE; the text changed 12 times.