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).

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


Driver private mapping data.


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


Length (in bytes) of the memory being accessed.


Type of access operation. Possible values are:


Memory access.


Lock the memory being accessed.


Unlock the memory being accessed.


Direction of access. Possible values are:


Read access attempted.


Write access attempted.


Execution access attempted.

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:


Successful completion.


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

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

January 17, 1997 OmniOS