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