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.Dd March 13, 2024
.Dt BUS_MAP_RESOURCE 9
.Os
.Sh NAME
.Nm bus_map_resource , bus_unmap_resource , resource_init_map_request
.Nd map or unmap an active resource
.Sh SYNOPSIS
.In sys/param.h
.In sys/bus.h
.Pp
.In machine/bus.h
.In sys/rman.h
.In machine/resource.h
.Ft int
.Fo bus_map_resource
.Fa "device_t dev" "struct resource *r"
.Fa "struct resource_map_request *args" "struct resource_map *map"
.Fc
.Ft int
.Fo bus_unmap_resource
.Fa "device_t dev" "struct resource *r" "struct resource_map *map"
.Fc
.Ft void
.Fn resource_init_map_request "struct resource_map_request *args"
.Sh DESCRIPTION
These functions create or destroy a mapping of a previously activated
resource.
Mappings permit CPU access to the resource via the
.Xr bus_space 9
API.
.Pp
The arguments are as follows:
.Bl -tag -width indent
.It Fa dev
The device that owns the resource.
.It Fa r
A pointer to the
.Vt "struct resource"
returned by
.Xr bus_alloc_resource 9 .
.It Fa args
A set of optional properties to apply when creating a mapping.
This argument can be set to
.Dv NULL
to request a mapping of the entire resource with the default properties.
.It Fa map
The resource mapping to create or destroy.
.El
.Ss Resource Mappings
Resource mappings are described by a
.Vt "struct resource_map"
object.
This structure contains a
.Xr bus_space 9
tag and handle in the
.Va r_bustag
and
.Va r_bushandle
members that can be used for CPU access to the mapping.
The structure also contains a
.Va r_vaddr
member which contains the virtual address of the mapping if one exists.
.Pp
The wrapper API for
.Vt "struct resource"
objects described in
.Xr bus_activate_resource 9
can also be used with
.Vt "struct resource_map" .
For example,
a pointer to a mapping object can be passed as the first argument to
.Fn bus_read_4 .
This wrapper API is preferred over using the
.Va r_bustag
and
.Va r_bushandle
members directly.
.Ss Optional Mapping Properties
The
.Vt "struct resource_map_request"
object passed in
.Fa args
can be used to specify optional properties of a mapping.
The structure must be initialized by invoking
.Fn resource_init_map_request .
Properties are then specified by setting one or more of these members:
.Bl -tag -width indent
.It Va offset , length
These two members specify a region of the resource to map.
By default a mapping is created for the entire resource.
The
.Va offset
is relative to the start of the resource.
.It Va memattr
Specifies a memory attribute to use when mapping the resource.
By default memory mappings use the
.Dv VM_MEMATTR_UNCACHEABLE
attribute.
.El
.Sh RETURN VALUES
Zero is returned on success, otherwise an error is returned.
.Sh EXAMPLES
This maps a PCI memory BAR with the write-combining memory attribute and
reads the first 32-bit word:
.Bd -literal
	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);
.Ed
.Sh SEE ALSO
.Xr bus_activate_resource 9 ,
.Xr bus_alloc_resource 9 ,
.Xr bus_space 9 ,
.Xr device 9 ,
.Xr driver 9
.Sh AUTHORS
This manual page was written by
.An John Baldwin Aq Mt jhb@FreeBSD.org .