i2c: Stop using the redundant client list

The i2c_adapter.clients list of i2c_client nodes duplicates driver
model state.  This patch starts removing that list, letting us remove
most existing users of those i2c-core lists.

 * The core I2C code now iterates over the driver model's list instead
   of the i2c-internal one in some places where it's safe:
      - Passing a command/ioctl to each client, a mechanims
        used almost exclusively by DVB adapters;
      - Device address checking, in both i2c-core and i2c-dev.

 * Provide i2c_verify_client() to use with driver model iterators.

 * Flag the relevant i2c_adapter and i2c_client fields as deprecated,
   to help prevent new users from appearing.

For the moment the list needs to stick around, since some issues show
up when deleting devices created by legacy I2C drivers.  (They don't
follow standard driver model rules.  Removing those devices can cause
self-deadlocks.)

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Jean Delvare <khali@linux-fr.org>

1 files changed, 5 insertions, 3 deletions

diff --git a/include/linux/i2c.h b/include/linux/i2c.h
index 0fc59efd80e4..731928ae972c 100644
--- a/include/linux/i2c.h
+++ b/include/linux/i2c.h
@@ -158,7 +158,7 @@ struct i2c_driver {
  * @irq: indicates the IRQ generated by this device (if any)
  * @driver_name: Identifies new-style driver used with this device; also
  *	used as the module name for hotplug/coldplug modprobe support.
- * @list: list of active/busy clients
+ * @list: list of active/busy clients (DEPRECATED)
  * @released: used to synchronize client releases & detaches and references
  *
  * An i2c_client identifies a single device (i.e. chip) connected to an
@@ -176,11 +176,13 @@ struct i2c_client {
 	struct device dev;		/* the device structure		*/
 	int irq;			/* irq issued by device (or -1) */
 	char driver_name[KOBJ_NAME_LEN];
-	struct list_head list;
+	struct list_head list;		/* DEPRECATED */
 	struct completion released;
 };
 #define to_i2c_client(d) container_of(d, struct i2c_client, dev)
 
+extern struct i2c_client *i2c_verify_client(struct device *dev);
+
 static inline struct i2c_client *kobj_to_i2c_client(struct kobject *kobj)
 {
 	struct device * const dev = container_of(kobj, struct device, kobj);
@@ -315,7 +317,7 @@ struct i2c_adapter {
 	struct device dev;		/* the adapter device */
 
 	int nr;
-	struct list_head clients;
+	struct list_head clients;	/* DEPRECATED */
 	char name[48];
 	struct completion dev_released;
 };