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