Merge rsync://rsync.kernel.org/pub/scm/linux/kernel/git/torvalds/linux-2.6

[pandora-kernel.git] / Documentation / i2c / writing-clients

diff --git a/Documentation/i2c/writing-clients b/Documentation/i2c/writing-clients
index 0772757..3a057c8 100644 (file)
--- a/Documentation/i2c/writing-clients
+++ b/Documentation/i2c/writing-clients
@@ -25,27 +25,20 @@ routines, a client structure specific information like the actual I2C
 address.
 
 static struct i2c_driver foo_driver = {
-       .owner          = THIS_MODULE,
-       .name           = "Foo version 2.3 driver",
-       .flags          = I2C_DF_NOTIFY,
+       .driver = {
+               .name   = "foo",
+       },
        .attach_adapter = &foo_attach_adapter,
        .detach_client  = &foo_detach_client,
        .command        = &foo_command /* may be NULL */
 }
  
-The name can be chosen freely, and may be upto 40 characters long. Please
-use something descriptive here.
-
-Don't worry about the flags field; just put I2C_DF_NOTIFY into it. This
-means that your driver will be notified when new adapters are found.
-This is almost always what you want.
+The name field must match the driver name, including the case. It must not
+contain spaces, and may be up to 31 characters long.
 
 All other fields are for call-back functions which will be explained 
 below.
 
-There use to be two additional fields in this structure, inc_use et dec_use,
-for module usage count, but these fields were obsoleted and removed.
-
 
 Extra client data
 =================
@@ -58,6 +51,7 @@ be very useful.
 An example structure is below.
 
   struct foo_data {
+    struct i2c_client client;
     struct semaphore lock; /* For ISA access in `sensors' drivers. */
     int sysctl_id;         /* To keep the /proc directory entry for 
                               `sensors' drivers. */
@@ -275,6 +269,7 @@ For now, you can ignore the `flags' parameter. It is there for future use.
     if (is_isa) {
 
       /* Discard immediately if this ISA range is already used */
+      /* FIXME: never use check_region(), only request_region() */
       if (check_region(address,FOO_EXTENT))
         goto ERROR0;
 
@@ -310,22 +305,15 @@ For now, you can ignore the `flags' parameter. It is there for future use.
        client structure, even though we cannot fill it completely yet.
        But it allows us to access several i2c functions safely */
     
-    /* Note that we reserve some space for foo_data too. If you don't
-       need it, remove it. We do it here to help to lessen memory
-       fragmentation. */
-    if (! (new_client = kmalloc(sizeof(struct i2c_client) + 
-                                sizeof(struct foo_data),
-                                GFP_KERNEL))) {
+    if (!(data = kzalloc(sizeof(struct foo_data), GFP_KERNEL))) {
       err = -ENOMEM;
       goto ERROR0;
     }
 
-    /* This is tricky, but it will set the data to the right value. */
-    client->data = new_client + 1;
-    data = (struct foo_data *) (client->data);
+    new_client = &data->client;
+    i2c_set_clientdata(new_client, data);
 
     new_client->addr = address;
-    new_client->data = data;
     new_client->adapter = adapter;
     new_client->driver = &foo_driver;
     new_client->flags = 0;
@@ -420,7 +408,7 @@ For now, you can ignore the `flags' parameter. It is there for future use.
         release_region(address,FOO_EXTENT);
     /* SENSORS ONLY END */
     ERROR1:
-      kfree(new_client);
+      kfree(data);
     ERROR0:
       return err;
   }
@@ -451,7 +439,7 @@ much simpler than the attachment code, fortunately!
       release_region(client->addr,LM78_EXTENT);
     /* HYBRID SENSORS CHIP ONLY END */
 
-    kfree(client); /* Frees client data too, if allocated at the same time */
+    kfree(i2c_get_clientdata(client));
     return 0;
   }
 
@@ -504,17 +492,13 @@ Note that some functions are marked by `__init', and some data structures
 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
@@ -576,12 +560,12 @@ SMBus communication
   extern s32 i2c_smbus_write_block_data(struct i2c_client * client,
                                         u8 command, u8 length,
                                         u8 *values);
+  extern s32 i2c_smbus_read_i2c_block_data(struct i2c_client * client,
+                                           u8 command, u8 *values);
 
 These ones were removed in Linux 2.6.10 because they had no users, but could
 be added back later if needed:
 
-  extern s32 i2c_smbus_read_i2c_block_data(struct i2c_client * client,
-                                           u8 command, u8 *values);
   extern s32 i2c_smbus_read_block_data(struct i2c_client * client,
                                        u8 command, u8 *values);
   extern s32 i2c_smbus_write_i2c_block_data(struct i2c_client * client,