Loadable Driver Interfaces

Device drivers must be dynamically loadable. Drivers should also be unloadable to help conserve memory resources. Drivers that can be unloaded are also easier to test, debug, and patch.

Each device driver is required to implement _init(9E), _fini(9E), and _info(9E) entry points to support driver loading and unloading. The following example shows a typical implementation of loadable driver interfaces.

static void *statep;                /* for soft state routines */
static struct cb_ops xx_cb_ops;     /* forward reference */
static struct dev_ops xx_ops = {
    DEVO_REV,
    0,
    xxgetinfo,
    nulldev,
    xxprobe,
    xxattach,
    xxdetach,
    xxreset,
    nodev,
    &xx_cb_ops,
    NULL,
    xxpower,
    ddi_quiesce_not_needed,
};

static struct modldrv modldrv = {
    &mod_driverops,
    "xx driver v1.0",
    &xx_ops
};

static struct modlinkage modlinkage = {
    MODREV_1,
    &modldrv,
    NULL
};

int
_init(void)
{
    int error;
    ddi_soft_state_init(&statep, sizeof (struct xxstate),
        estimated_number_of_instances);
    /* further per-module initialization if necessary */
    error = mod_install(&modlinkage);
    if (error != 0) {
        /* undo any per-module initialization done earlier */
        ddi_soft_state_fini(&statep);
    }
    return (error);
}

int
_fini(void)
{
    int error;
    error = mod_remove(&modlinkage);
    if (error == 0) {
        /* release per-module resources if any were allocated */
        ddi_soft_state_fini(&statep);
    }
    return (error);
}

int
_info(struct modinfo *modinfop)
{
    return (mod_info(&modlinkage, modinfop));
}