+/**
+ * i2c_add_adapter - declare i2c adapter, use dynamic bus number
+ * @adapter: the adapter to add
+ *
+ * This routine is used to declare an I2C adapter when its bus number
+ * doesn't matter. Examples: for I2C adapters dynamically added by
+ * USB links or PCI plugin cards.
+ *
+ * When this returns zero, a new bus number was allocated and stored
+ * in adap->nr, and the specified adapter became available for clients.
+ * Otherwise, a negative errno value is returned.
+ */
+int i2c_add_adapter(struct i2c_adapter *adapter)
+{
+ int id, res = 0;
+
+retry:
+ if (idr_pre_get(&i2c_adapter_idr, GFP_KERNEL) == 0)
+ return -ENOMEM;
+
+ mutex_lock(&core_lists);
+ /* "above" here means "above or equal to", sigh */
+ res = idr_get_new_above(&i2c_adapter_idr, adapter,
+ __i2c_first_dynamic_bus_num, &id);
+ mutex_unlock(&core_lists);
+
+ if (res < 0) {
+ if (res == -EAGAIN)
+ goto retry;
+ return res;
+ }
+
+ adapter->nr = id;
+ return i2c_register_adapter(adapter);
+}
+EXPORT_SYMBOL(i2c_add_adapter);
+
+/**
+ * i2c_add_numbered_adapter - declare i2c adapter, use static bus number
+ * @adap: the adapter to register (with adap->nr initialized)
+ *
+ * This routine is used to declare an I2C adapter when its bus number
+ * matters. Example: for I2C adapters from system-on-chip CPUs, or
+ * otherwise built in to the system's mainboard, and where i2c_board_info
+ * is used to properly configure I2C devices.
+ *
+ * If no devices have pre-been declared for this bus, then be sure to
+ * register the adapter before any dynamically allocated ones. Otherwise
+ * the required bus ID may not be available.
+ *
+ * When this returns zero, the specified adapter became available for
+ * clients using the bus number provided in adap->nr. Also, the table
+ * of I2C devices pre-declared using i2c_register_board_info() is scanned,
+ * and the appropriate driver model device nodes are created. Otherwise, a
+ * negative errno value is returned.
+ */
+int i2c_add_numbered_adapter(struct i2c_adapter *adap)
+{
+ int id;
+ int status;
+
+ if (adap->nr & ~MAX_ID_MASK)
+ return -EINVAL;
+
+retry:
+ if (idr_pre_get(&i2c_adapter_idr, GFP_KERNEL) == 0)
+ return -ENOMEM;
+
+ mutex_lock(&core_lists);
+ /* "above" here means "above or equal to", sigh;
+ * we need the "equal to" result to force the result
+ */
+ status = idr_get_new_above(&i2c_adapter_idr, adap, adap->nr, &id);
+ if (status == 0 && id != adap->nr) {
+ status = -EBUSY;
+ idr_remove(&i2c_adapter_idr, id);
+ }
+ mutex_unlock(&core_lists);
+ if (status == -EAGAIN)
+ goto retry;
+
+ if (status == 0)
+ status = i2c_register_adapter(adap);
+ return status;
+}
+EXPORT_SYMBOL_GPL(i2c_add_numbered_adapter);
+