devmap_dup() Entry Point

The devmap_dup(9E) entry point is called when a device mapping is duplicated, for example, by a user process that calls fork(2). The driver is expected to generate new driver private data for the new mapping.

The syntax fordevmap_dup() is as follows:

int xxdevmap_dup(devmap_cookie_t handle, void *devprivate,
    devmap_cookie_t new-handle, void **new-devprivate);

where:

handle

Mapping handle of the mapping being duplicated.

new-handle

Mapping handle of the mapping that was duplicated.

devprivate

Pointer to the driver private data associated with the mapping being duplicated.

*new-devprivate

Should be set to point to the new driver private data for the new mapping.

Mappings that have been created with devmap_dup() by default have their mapping translations invalidated. Invalid mapping translations force a call to the devmap_access(9E) entry point the first time the mapping is accessed.

The following example shows a typical devmap_dup() routine.

Example 11–4 Using the devmap_dup() Routine

static int
xxdevmap_dup(devmap_cookie_t handle, void *devprivate,
    devmap_cookie_t new_handle, void **new_devprivate)
{
    struct xxctx *ctxp = devprivate;
    struct xxstate *xsp = ctxp->xsp;
    struct xxctx *newctx;
    /* Create a new context for the duplicated mapping */
    newctx = kmem_alloc(sizeof (struct xxctx), KM_SLEEP);
    newctx->xsp = xsp;
    newctx->handle = new_handle;
    newctx->offset = ctxp->offset;
    newctx->flags = ctxp->flags;
    newctx->len = ctxp->len;
    mutex_enter(&xsp->ctx_lock);
    if (ctxp->flags & MAP_PRIVATE) {
        newctx->context = kmem_alloc(XXCTX_SIZE, KM_SLEEP);
        bcopy(ctxp->context, newctx->context, XXCTX_SIZE);
    } else {
        newctx->context = xsp->ctx_shared;
    }
    mutex_exit(&xsp->ctx_lock);
    *new_devprivate = newctx;
    return(0);
}