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


NAME


devmap_do_ctxmgt - perform device context switching on a mapping

SYNOPSIS


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


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


INTERFACE LEVEL


Solaris DDI specific (Solaris DDI).

PARAMETERS


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.


devmap_contextmgt
The address of driver function that the system will
call to perform context switching on a mapping. See
devmap_contextmgt(9E) for details.


type
Type of access operation. Provided by
devmap_access(9E). Should not be modified.


rw
Direction of access. Provided by
devmap_access(9E). Should not be modified.


DESCRIPTION


Device drivers call devmap_do_ctxmgt() in the devmap_access(9E) entry
point to perform device context switching on a mapping.
devmap_do_ctxmgt() passes a pointer to a driver supplied callback
function, devmap_contextmgt(9E), to the system that will perform the
actual device context switching. If devmap_contextmgt(9E) is not a valid
driver callback function, the system will fail the memory access
operation which will result in a SIGSEGV or SIGBUS signal being delivered
to the process.


devmap_do_ctxmgt() performs context switching on the mapping object
identified by dhp and pvtp in the range specified by off and len. The
arguments dhp, pvtp, type, and rw are provided by the devmap_access(9E)
entry point and must not be modified. The range from off to off+len must
support context switching.


The system will pass through dhp, pvtp, off, len, type, and rw to
devmap_contextmgt(9E) in order to perform the actual device context
switching. The return value from devmap_contextmgt(9E) will be returned
directly to devmap_do_ctxmgt().

RETURN VALUES


0
Successful completion.


Non-zero
An error occurred.


CONTEXT


devmap_do_ctxmgt() must be called from the driver's devmap_access(9E)
entry point.

EXAMPLES


Example 1: Using devmap_do_ctxmgt in the devmap_access entry point.




The following shows an example of using devmap_do_ctxmgt() in the
devmap_access(9E) entry point.


...
#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_access(9E), devmap_contextmgt(9E), devmap_default_access(9F)


Writing Device Drivers


January 22, 1997 DEVMAP_DO_CTXMGT(9F)