segmap(9E) Driver Entry Points segmap(9E)NAMEsegmap - map device memory into user space
SYNOPSIS
#include <sys/types.h>
#include <sys/mman.h>
#include <sys/param.h>
#include <sys/vm.h>
#include <sys/ddi.h>
#include <sys/sunddi.h>
int prefixsegmap(dev_t dev, off_t off, struct as *asp, caddr_t *addrp,
off_t len, unsigned int prot, unsigned int maxprot, unsigned int flags,
cred_t *cred_p);
INTERFACE LEVEL
Architecture independent level 2 (DKI only).
ARGUMENTS
dev Device whose memory is to be mapped.
off Offset within device memory at which mapping begins.
asp Pointer to the address space into which the device mem‐
ory should be mapped.
addrp Pointer to the address in the address space to 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. Possible
settings are:
"small and bold"ReadTaccess is desired.
PROT_WRITE Write access is desired.
PROT_EXEC Execute access is desired.
PROT_USER User-level access is desired (the map‐
ping 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. Possible values are
(other bits may be set):
MAP_SHARED Changes should be shared.
MAP_PRIVATE Changes are private.
cred_p Pointer to the user credentials structure.
DESCRIPTION
The segmap() entry point is an optional routine for character drivers
that support memory mapping. The mmap(2) system call, when applied to
a character special file, allows device memory to be mapped into user
space for direct access by the user application.
Typically, a character driver that needs to support the mmap(2) system
call supplies either an devmap(9E) entry point, or both an devmap(9E)
and a segmap() entry point routine (see the devmap(9E) reference
page). If no segmap() entry point is provided for the driver,
devmap_setup(9F) is used as a default.
A driver for a memory-mapped device would provide a segmap() entry
point if it:
· needs to maintain a separate context for each user mapping. See
devmap_setup(9F) for details.
· needs to assign device access attributes to the user mapping.
The responsibilities of a segmap() entry point are:
· Verify that the range, defined by offset and len, to be mapped
is valid for the device. Typically, this task is performed by
calling the devmap(9E) entry point. Note that if you are using
ddi_devmap_segmap(9F) or devmap_setup(9F) to set up the mapping,
it will call your devmap(9E) entry point for you to validate the
range to be mapped.
· Assign device access attributes to the mapping. See
ddi_devmap_segmap(9F), and ddi_device_acc_attr(9S) for details.
· Set up device contexts for the user mapping if your device
requires context switching. See devmap_setup(9F) for details.
·
Perform the mapping with ddi_devmap_segmap(9F), or devmap_set‐
up(9F) and return the status if it fails.
RETURN VALUES
The segmap() routine should return 0 if the driver is successful in
performing the memory map of its device address space into the speci‐
fied address space.
The segmap() must return an error number on failure. For example, valid
error numbers would be ENXIO if the offset/length pair specified
exceeds the limits of the device memory, or EINVAL if the driver
detects an invalid type of mapping attempted.
If one of the mapping routines ddi_devmap_segmap() or devmap_set‐
up()fails, you must return the error number returned by the respective
routine.
SEE ALSOmmap(2), devmap(9E), devmap_setup(9F), ddi_devmap_segmap(9F),
ddi_device_acc_attr(9S)
Writing Device Drivers
SunOS 5.10 14 Jan 1997 segmap(9E)
