illumos: manual page: devmap

DEVMAP_SETUP(9F) Kernel Functions for Drivers DEVMAP_SETUP(9F)

NAME

devmap_setup, ddi_devmap_segmap - set up a user mapping to device memory
using the devmap framework

SYNOPSIS

#include <sys/ddi.h>
#include <sys/sunddi.h>

int devmap_setup(dev_t dev, offset_t off, ddi_as_handle_t as,
caddr_t *addrp, size_tlen, uint_t prot, uint_t maxprot,
uint_t flags, cred_t *cred);

int ddi_devmap_segmap(dev_t dev, off_t off, ddi_as_handle_t as,
caddr_t *addrp, off_tlen, uint_t prot, uint_t maxprot,
uint_t flags, cred_t *cred);

INTERFACE LEVEL

illumos DDI specific (illumos DDI).

PARAMETERS

dev
Device whose memory is to be mapped.

off
User offset within the logical device memory at which the
mapping begins.

as
An opaque data structure that describes the address space
into which the device memory should be mapped.

addrp
Pointer to the starting address in the address space into
which the device memory should be mapped.

len
Length (in bytes) of the memory to be mapped.

prot
A bit field that specifies the protections. Some possible
settings combinations are:

PROT_READ
Read access is desired.

PROT_WRITE
Write access is desired.

PROT_EXEC
Execute access is desired.

PROT_USER
User-level access is desired (the mapping is
being done as a result of a mmap(2) system
call).

PROT_ALL
All access is desired.

maxprot
Maximum protection flag possible for attempted mapping; the
PROT_WRITE bit may be masked out if the user opened the
special file read-only.

flags
Flags indicating type of mapping. The following flags can be
specified:

MAP_PRIVATE
Changes are private.

MAP_SHARED
Changes should be shared.

MAP_FIXED
The user specified an address in *addrp
rather than letting the system choose an
address.

cred
Pointer to the user credential structure.

DESCRIPTION

devmap_setup() and ddi_devmap_segmap() allow device drivers to use the
devmap framework to set up user mappings to device memory. The devmap
framework provides several advantages over the default device mapping
framework that is used by ddi_segmap(9F) or ddi_segmap_setup(9F). Device
drivers should use the devmap framework, if the driver wants to:

o use an optimal MMU pagesize to minimize address translations,

o conserve kernel resources,

o receive callbacks to manage events on the mapping,

o export kernel memory to applications,

o set up device contexts for the user mapping if the device
requires context switching,

o assign device access attributes to the user mapping, or

o change the maximum protection for the mapping.

devmap_setup() must be called in the segmap(9E) entry point to establish
the mapping for the application. ddi_devmap_segmap() can be called in, or
be used as, the segmap(9E) entry point. The differences between
devmap_setup() and ddi_devmap_segmap() are in the data type used for off
and len.

When setting up the mapping, devmap_setup() and ddi_devmap_segmap() call
the devmap(9E) entry point to validate the range to be mapped. The
devmap(9E) entry point also translates the logical offset (as seen by the
application) to the corresponding physical offset within the device
address space. If the driver does not provide its own devmap(9E) entry
point, EINVAL will be returned to the mmap(2) system call.

RETURN VALUES

0
Successful completion.

Non-zero
An error occurred. The return value of devmap_setup() and
ddi_devmap_segmap() should be used directly in the
segmap(9E) entry point.

CONTEXT

devmap_setup() and ddi_devmap_segmap() can be called from user or kernel
context only.