NAME

mapdev_access - device mapping access entry point

SYNOPSIS

#include <sys/sunddi.h>

int prefixmapdev_access(ddi_mapdev_handle_t handle, void * devprivate,off_t offset);

INTERFACE LEVEL

Solaris DDI specific (Solaris DDI).

ARGUMENTS

handle

An opaque pointer to a device mapping.

devprivate

Driver private mapping data from ddi_mapdev(9F).

offset

The offset within device memory at which the access occurred.

DESCRIPTION

mapdev_access( ) is called when an access is made to a mapping that has either been newly created with ddi_mapdev(9F) or that has been enabled with a call to ddi_mapdev_intercept(9F).

mapdev_access( ) is passed the handle of the mapped object on which an access has occurred. This handle uniquely identifies the mapping and is used as an argument to ddi_mapdev_intercept(9F) or ddi_mapdev_nointercept(9F) to control whether or not future accesses to the mapping will cause mapdev_access( ) to be called. In general, mapdev_access( ) should call ddi_mapdev_intercept( ) on the mapping that is currently in use and then call ddi_mapdev_nointercept( ) on the mapping that generated this call to mapdev_access( ). This will ensure that a call to mapdev_access( ) will be generated for the current mapping next time it is accessed.

mapdev_access( ) must at least call ddi_mapdev_nointercept( ) with offset passed in in order for the access to succeed. A request to allow accesses affects the entire page containing the offset.

Accesses to portions of mappings that have been disabled by a call to ddi_mapdev_nointercept( ) will not generate a call to mapdev_access( ). A subsequent call to ddi_mapdev_intercept( ) will enable mapdev_access( ) to be called again.

A non-zero return value from mapdev_access( ) will cause the corresponding operation to fail. The failure may result in a SIGSEGV or SIGBUS signal being delivered to the process.

RETURN VALUES

mapdev_access( ) should return 0 on success, -1 if there was a hardware error, or the return value from ddi_mapdev_intercept( ) or ddi_mapdev_nointercept( ).

EXAMPLE

The following shows an example of managing a device context that is one page in length.

ddi_mapdev_handle_t cur_hdl;

static int

xxmapdev_access(ddi_mapdev_handle_t handle, void * devprivate,
  off_t offset)
{
        int     err;

        /* enable calls to mapdev_access for the current mapping * /
        if (cur_hdl != NULL) {
                if ((err = ddi_mapdev_intercept(cur_hdl, off, 0)) != 0)
                        return (err);
        }

/* Switch device context - device dependent* /

        ...

/* Make handle the new current mapping * /

        cur_hdl = handle;

/*

        * Disable callbacks and complete the access for the
        * mapping that generated this callback.
        * /

return (ddi_mapdev_nointercept(handle, off, 0));

}

CONTEXT

This function is called from user context only.

SEE ALSO

mmap(2), mapdev_dup (9E),mapdev_free(9E), segmap (9E),ddi_mapdev(9F), ddi_mapdev_intercept(9F), ddi_mapdev_nointercept(9F), ddi_mapdev_ctl(9S),

Writing Device Drivers