[PATCH] i2c: update i2c_driver.command documentation

Document i2c_driver.command as being deprecated, and don't suggest an
empty implementation of this callback as it doesn't make any sense.

Signed-off-by: Jean Delvare <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

Documentation/i2c/writing-clients

···
 by `__init_data'.  Hose functions and structures can be removed after
 kernel booting (or module loading) is completed.
 
+
 Command function
 ================
 
 A generic ioctl-like function call back is supported. You will seldom
-need this. You may even set it to NULL.
-
-  /* No commands defined */
-  int foo_command(struct i2c_client *client, unsigned int cmd, void *arg)
-  {
-    return 0;
-  }
+need this, and its use is deprecated anyway, so newer design should not
+use it. Set it to NULL.
 
 
 Sending and receiving