DEVMAP_ACCESS(9E) Driver Entry Points DEVMAP_ACCESS(9E)


NAME


devmap_access - device mapping access entry point

SYNOPSIS


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


int prefixdevmap_access(devmap_cookie_t dhp, void *pvtp,
offset_t off, size_t len, uint_t type, uint_t rw);


INTERFACE LEVEL


Solaris DDI specific (Solaris DDI).

ARGUMENTS


dhp
An opaque mapping handle that the system uses to describe the
mapping.


pvtp
Driver private mapping data.


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


len
Length (in bytes) of the memory being accessed.


type
Type of access operation. Possible values are:

DEVMAP_ACCESS
Memory access.


DEVMAP_LOCK
Lock the memory being accessed.


DEVMAP_UNLOCK
Unlock the memory being accessed.


rw
Direction of access. Possible values are:

DEVMAP_READ
Read access attempted.


DEVMAP_WRITE
Write access attempted.


DEVMAP_EXEC
Execution access attempted.


DESCRIPTION


The devmap_access() entry point is an optional routine. It notifies
drivers whenever an access is made to a mapping described by dhp that
has not been validated or does not have sufficient protection for the
access. The system expects devmap_access() to call either
devmap_do_ctxmgt(9F) or devmap_default_access(9F) to load the memory
address translations before it returns. For mappings that support context
switching, device drivers should call devmap_do_ctxmgt(9F). For mappings
that do not support context switching, the drivers should call
devmap_default_access(9F).


In devmap_access(), drivers perform memory access related operations
such as context switching, checking the availability of the memory
object, and locking and unlocking the memory object being accessed. The
devmap_access() entry point is set to NULL if no operations need to be
performed.


pvtp is a pointer to the driver's private mapping data that was allocated
and initialized in the devmap_map(9E) entry point.


off and len define the range to be affected by the operations in
devmap_access(). type defines the type of operation that device drivers
should perform on the memory object. If type is either DEVMAP_LOCK or
DEVMAP_UNLOCK, the length passed to either devmap_do_ctxmgt(9F) or
devmap_default_access(9F) must be same as len. rw specifies the direction
of access on the memory object.


A non-zero return value from devmap_access() may result in a SIGSEGV or
SIGBUS signal being delivered to the process.

RETURN VALUES


devmap_access() returns the following values:

0
Successful completion.


Non-zero
An error occurred. The return value from
devmap_do_ctxmgt(9F) or devmap_default_access(9F) should be
returned.


EXAMPLES


Example 1 devmap_access() entry point


The following is an example of the devmap_access() entry point. If the
mapping supports context switching, devmap_access() calls
devmap_do_ctxmgt(9F). Otherwise, devmap_access() calls
devmap_default_access(9F).


...
#define OFF_DO_CTXMGT 0x40000000
#define OFF_NORMAL 0x40100000
#define CTXMGT_SIZE 0x100000
#define NORMAL_SIZE 0x100000

/*
* Driver devmap_contextmgt(9E) callback function.
*/
static int
xx_context_mgt(devmap_cookie_t dhp, void *pvtp, offset_t offset,
size_t length, uint_t type, uint_t rw)
{
......
/*
* see devmap_contextmgt(9E) for an example
*/
}

/*
* Driver devmap_access(9E) entry point
*/
static int
xxdevmap_access(devmap_cookie_t dhp, void *pvtp, offset_t off,
size_t len, uint_t type, uint_t rw)
{
offset_t diff;
int err;

/*
* check if off is within the range that supports
* context management.
*/
if ((diff = off - OFF_DO_CTXMG) >= 0 && diff < CTXMGT_SIZE) {
/*
* calculates the length for context switching
*/
if ((len + off) > (OFF_DO_CTXMGT + CTXMGT_SIZE))
return (-1);
/*
* perform context switching
*/
err = devmap_do_ctxmgt(dhp, pvtp, off, len, type,
rw, xx_context_mgt);
/*
* check if off is within the range that does normal
* memory mapping.
*/
} else if ((diff = off - OFF_NORMAL) >= 0 && diff < NORMAL_SIZE) {
if ((len + off) > (OFF_NORMAL + NORMAL_SIZE))
return (-1);
err = devmap_default_access(dhp, pvtp, off, len, type, rw);
} else
return (-1);

return (err);
}


SEE ALSO


devmap_map(9E), devmap_default_access(9F), devmap_do_ctxmgt(9F),
devmap_callback_ctl(9S)


Writing Device Drivers


January 17, 1997 DEVMAP_ACCESS(9E)