Writing Device Drivers

_init() Example

The following example shows a typical _init(9E) interface.

Example 6–2 _init() Function

static void *xxstatep;
    int error;
    const int max_instance = 20;    /* estimated max device instances */

    ddi_soft_state_init(&xxstatep, sizeof (struct xxstate), max_instance);
    error = mod_install(&xxmodlinkage);
    if (error != 0) {
         * Cleanup after a failure
    return (error);

The driver should perform any one-time resource allocation or data initialization during driver loading in _init(). For example, the driver should initialize any mutexes global to the driver in this routine. The driver should not, however, use _init(9E) to allocate or initialize anything that has to do with a particular instance of the device. Per-instance initialization must be done in attach(9E). For example, if a driver for a printer can handle more than one printer at the same time, that driver should allocate resources specific to each printer instance in attach().

Note –

Once _init(9E) has called mod_install(9F), the driver should not change any of the data structures attached to the modlinkage(9S) structure because the system might make copies or change the data structures.