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man pages section 9: DDI and DKI Driver Entry Points

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Updated: Thursday, June 13, 2019
 
 

segmap(9E)

Name

segmap - 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 memory 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:

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. 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:

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 specified 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_setup()fails, you must return the error number returned by the respective routine.

See Also

mmap(2), devmap(9E), ddi_devmap_segmap(9F), devmap_setup(9F), ddi_device_acc_attr(9S)

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