devmap_contextmgt - driver callback function for context management

#include <sys/ddi.h>
#include <sys/sunddi.h>
int devmap_contextmgt(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.

devmap_contextmgt() is a driver-supplied function that performs device context switching on a mapping. Device drivers pass devmap_contextmgt() as an argument to devmap_do_ctxmgt(9F) in the devmap_access(9E) entry point. The system will call devmap_contextmgt() when memory is accessed. The system expects devmap_contextmgt() to load the memory address translations of the mapping by calling devmap_load(9F) before returning.

dhp uniquely identifies the mapping and is used as an argument to devmap_load(9F) to validate the mapping. off and len define the range to be affected by the operations in devmap_contextmgt().

The driver must check if there is already a mapping established at off that needs to be unloaded. If a mapping exists at off, devmap_contextmgt() must call devmap_unload(9F) on the current mapping. devmap_unload(9F) must be followed by devmap_load() on the mapping that generated this call to devmap_contextmgt(). devmap_unload(9F) unloads the current mapping so that a call to devmap_access(9E), which causes the system to call devmap_contextmgt(), will be generated the next time the mapping is accessed.

pvtp is a pointer to the driver's private mapping data that was allocated and initialized in the devmap_map(9E) entry point. 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_unload(9F) or devmap_load(9F) must be same as len. rw specifies the access direction on the memory object.

A non-zero return value from devmap_contextmgt() will be returned to devmap_access(9E) and will cause the corresponding operation to fail. The failure may result in a SIGSEGV or SIGBUS signal being delivered to the process.

Successful completion.


An error occurred.

Example 1 managing a device context

The following shows an example of managing a device context.

struct xxcontext cur_ctx;
static int
xxdevmap_contextmgt(devmap_cookie_t dhp, void *pvtp, offset_t off,
	size_t len, uint_t type, uint_t rw)
    devmap_cookie_t cur_dhp;
    struct xxpvtdata *p;
    struct xxpvtdata *pvp = (struct xxpvtdata *)pvtp;
    struct xx_softc  *softc = pvp->softc;
    int    err;
     * invalidate the translations of current context before
     * switching context.
    if (cur_ctx != NULL && cur_ctx != pvp->ctx) {
        p = cur_ctx->pvt;
        cur_dhp = p->dhp;
        if ((err = devmap_unload(cur_dhp, off, len)) != 0)
            return (err);
    /* Switch device context - device dependent*/
    /* Make handle the new current mapping */
    cur_ctx = pvp->ctx;
     * Load the address translations of the calling context.
    err = devmap_load(pvp->dhp, off, len, type, rw);
    return (err);

devmap_access(9E), devmap_do_ctxmgt(9F) devmap_load(9F), devmap_unload(9F)

Writing Device Drivers

January 16, 1997 OmniOS