i2c: Add i2c_add_numbered_adapter()

This adds a call, i2c_add_numbered_adapter(), registering an I2C adapter
with a specific bus number and then creating I2C device nodes for any
pre-declared devices on that bus.  It builds on previous patches adding
I2C probe() and remove() support, and that pre-declaration of devices.

This completes the core support for "new style" I2C device drivers.
Those follow the standard driver model for binding devices to drivers
(using probe and remove methods) rather than a legacy model (where the
driver tries to autoconfigure each bus, and registers devices itself).
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Jean Delvare <khali@linux-fr.org>

drivers/i2c/i2c-core.c

@@ -320,38 +320,19 @@ static void i2c_scan_static_board_info(struct i2c_adapter *adapter)
 	mutex_unlock(&__i2c_board_lock);
 }
 
-
-/* -----
- * i2c_add_adapter is called from within the algorithm layer,
- * when a new hw adapter registers. A new device is register to be
- * available for clients.
- */
-int i2c_add_adapter(struct i2c_adapter *adap)
+static int i2c_register_adapter(struct i2c_adapter *adap)
 {
-	int id, res = 0;
+	int res = 0;
 	struct list_head   *item;
 	struct i2c_driver  *driver;
 
-	mutex_lock(&core_lists);
-
-	if (idr_pre_get(&i2c_adapter_idr, GFP_KERNEL) == 0) {
-		res = -ENOMEM;
-		goto out_unlock;
-	}
-
-	res = idr_get_new(&i2c_adapter_idr, adap, &id);
-	if (res < 0) {
-		if (res == -EAGAIN)
-			res = -ENOMEM;
-		goto out_unlock;
-	}
-
-	adap->nr =  id & MAX_ID_MASK;
 	mutex_init(&adap->bus_lock);
 	mutex_init(&adap->clist_lock);
-	list_add_tail(&adap->list,&adapters);
 	INIT_LIST_HEAD(&adap->clients);
 
+	mutex_lock(&core_lists);
+	list_add_tail(&adap->list, &adapters);
+
 	/* Add the adapter to the driver core.
 	 * If the parent pointer is not set up,
 	 * we add this adapter to the host bus.
@@ -370,6 +351,10 @@ int i2c_add_adapter(struct i2c_adapter *adap)
 
 	dev_dbg(&adap->dev, "adapter [%s] registered\n", adap->name);
 
+	/* create pre-declared device nodes for new-style drivers */
+	if (adap->nr < __i2c_first_dynamic_bus_num)
+		i2c_scan_static_board_info(adap);
+
 	/* let legacy drivers scan this bus for matching devices */
 	list_for_each(item,&drivers) {
 		driver = list_entry(item, struct i2c_driver, list);
@@ -388,6 +373,93 @@ int i2c_add_adapter(struct i2c_adapter *adap)
 	goto out_unlock;
 }
 
+/**
+ * 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);
+
 int i2c_del_adapter(struct i2c_adapter *adap)
 {
 	struct list_head  *item, *_n;
@@ -452,7 +524,7 @@ int i2c_del_adapter(struct i2c_adapter *adap)
 	/* wait for sysfs to drop all references */
 	wait_for_completion(&adap->dev_released);
 
-	/* free dynamically allocated bus id */
+	/* free bus id */
 	idr_remove(&i2c_adapter_idr, adap->nr);
 
 	dev_dbg(&adap->dev, "adapter [%s] unregistered\n", adap->name);
@@ -493,6 +565,9 @@ int i2c_register_driver(struct module *owner, struct i2c_driver *driver)
 	driver->driver.owner = owner;
 	driver->driver.bus = &i2c_bus_type;
 
+	/* for new style drivers, when registration returns the driver core
+	 * will have called probe() for all matching-but-unbound devices.
+	 */
 	res = driver_register(&driver->driver);
 	if (res)
 		return res;
@@ -1377,7 +1452,6 @@ EXPORT_SYMBOL_GPL(i2c_adapter_dev_release);
 EXPORT_SYMBOL_GPL(i2c_adapter_class);
 EXPORT_SYMBOL_GPL(i2c_bus_type);
 
-EXPORT_SYMBOL(i2c_add_adapter);
 EXPORT_SYMBOL(i2c_del_adapter);
 EXPORT_SYMBOL(i2c_del_driver);
 EXPORT_SYMBOL(i2c_attach_client);

include/linux/i2c.h

@@ -363,6 +363,7 @@ struct i2c_client_address_data {
  */
 extern int i2c_add_adapter(struct i2c_adapter *);
 extern int i2c_del_adapter(struct i2c_adapter *);
+extern int i2c_add_numbered_adapter(struct i2c_adapter *);
 
 extern int i2c_register_driver(struct module *, struct i2c_driver *);
 extern int i2c_del_driver(struct i2c_driver *);