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devmap_do_ctxmgt - perform device context switching on a mapping

#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);

illumos DDI specific (illumos DDI). dhp pvtp off len devmap_contextmgt type rw 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().

0 Non-zero devmap_do_ctxmgt() must be called from the driver's devmap_access(9E) entry point. 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);
}

devmap_access(9E), devmap_contextmgt(9E), devmap_default_access(9F)

Writing Device Drivers