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devmap_access - device mapping access entry point

#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);

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

devmap_access() returns the following values: 0 Non-zero 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);
}

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

Writing Device Drivers