+/**
+ * register_con_driver - register console driver to console layer
+ * @csw: console driver
+ * @first: the first console to take over, minimum value is 0
+ * @last: the last console to take over, maximum value is MAX_NR_CONSOLES -1
+ *
+ * DESCRIPTION: This function registers a console driver which can later
+ * bind to a range of consoles specified by @first and @last. It will
+ * also initialize the console driver by calling con_startup().
+ */
+int register_con_driver(const struct consw *csw, int first, int last)
+{
+ struct module *owner = csw->owner;
+ struct con_driver *con_driver;
+ const char *desc;
+ int i, retval = 0;
+
+ if (!try_module_get(owner))
+ return -ENODEV;
+
+ acquire_console_sem();
+
+ for (i = 0; i < MAX_NR_CON_DRIVER; i++) {
+ con_driver = ®istered_con_driver[i];
+
+ /* already registered */
+ if (con_driver->con == csw)
+ retval = -EINVAL;
+ }
+
+ if (retval)
+ goto err;
+
+ desc = csw->con_startup();
+
+ if (!desc)
+ goto err;
+
+ retval = -EINVAL;
+
+ for (i = 0; i < MAX_NR_CON_DRIVER; i++) {
+ con_driver = ®istered_con_driver[i];
+
+ if (con_driver->con == NULL) {
+ con_driver->con = csw;
+ con_driver->desc = desc;
+ con_driver->node = i;
+ con_driver->flag = CON_DRIVER_FLAG_MODULE |
+ CON_DRIVER_FLAG_INIT;
+ con_driver->first = first;
+ con_driver->last = last;
+ retval = 0;
+ break;
+ }
+ }
+
+ if (retval)
+ goto err;
+
+ con_driver->dev = device_create(vtconsole_class, NULL,
+ MKDEV(0, con_driver->node),
+ "vtcon%i", con_driver->node);
+
+ if (IS_ERR(con_driver->dev)) {
+ printk(KERN_WARNING "Unable to create device for %s; "
+ "errno = %ld\n", con_driver->desc,
+ PTR_ERR(con_driver->dev));
+ con_driver->dev = NULL;
+ } else {
+ vtconsole_init_device(con_driver);
+ }
+
+err:
+ release_console_sem();
+ module_put(owner);
+ return retval;
+}
+EXPORT_SYMBOL(register_con_driver);
+
+/**
+ * unregister_con_driver - unregister console driver from console layer
+ * @csw: console driver
+ *
+ * DESCRIPTION: All drivers that registers to the console layer must
+ * call this function upon exit, or if the console driver is in a state
+ * where it won't be able to handle console services, such as the
+ * framebuffer console without loaded framebuffer drivers.
+ *
+ * The driver must unbind first prior to unregistration.
+ */
+int unregister_con_driver(const struct consw *csw)
+{
+ int i, retval = -ENODEV;
+
+ acquire_console_sem();
+
+ /* cannot unregister a bound driver */
+ if (con_is_bound(csw))
+ goto err;
+
+ for (i = 0; i < MAX_NR_CON_DRIVER; i++) {
+ struct con_driver *con_driver = ®istered_con_driver[i];
+
+ if (con_driver->con == csw &&
+ con_driver->flag & CON_DRIVER_FLAG_MODULE) {
+ vtconsole_deinit_device(con_driver);
+ device_destroy(vtconsole_class,
+ MKDEV(0, con_driver->node));
+ con_driver->con = NULL;
+ con_driver->desc = NULL;
+ con_driver->dev = NULL;
+ con_driver->node = 0;
+ con_driver->flag = 0;
+ con_driver->first = 0;
+ con_driver->last = 0;
+ retval = 0;
+ break;
+ }
+ }
+err:
+ release_console_sem();
+ return retval;
+}
+EXPORT_SYMBOL(unregister_con_driver);