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+Upgrading I2C Drivers to the new 2.6 Driver Model
+=================================================
+
+Ben Dooks <ben-linux@fluff.org>
+
+Introduction
+------------
+
+This guide outlines how to alter existing Linux 2.6 client drivers from
+the old to the new new binding methods.
+
+
+Example old-style driver
+------------------------
+
+
+struct example_state {
+ struct i2c_client client;
+ ....
+};
+
+static struct i2c_driver example_driver;
+
+static unsigned short ignore[] = { I2C_CLIENT_END };
+static unsigned short normal_addr[] = { OUR_ADDR, I2C_CLIENT_END };
+
+I2C_CLIENT_INSMOD;
+
+static int example_attach(struct i2c_adapter *adap, int addr, int kind)
+{
+ struct example_state *state;
+ struct device *dev = &adap->dev; /* to use for dev_ reports */
+ int ret;
+
+ state = kzalloc(sizeof(struct example_state), GFP_KERNEL);
+ if (state == NULL) {
+ dev_err(dev, "failed to create our state\n");
+ return -ENOMEM;
+ }
+
+ example->client.addr = addr;
+ example->client.flags = 0;
+ example->client.adapter = adap;
+
+ i2c_set_clientdata(&state->i2c_client, state);
+ strlcpy(client->i2c_client.name, "example", I2C_NAME_SIZE);
+
+ ret = i2c_attach_client(&state->i2c_client);
+ if (ret < 0) {
+ dev_err(dev, "failed to attach client\n");
+ kfree(state);
+ return ret;
+ }
+
+ dev = &state->i2c_client.dev;
+
+ /* rest of the initialisation goes here. */
+
+ dev_info(dev, "example client created\n");
+
+ return 0;
+}
+
+static int example_detach(struct i2c_client *client)
+{
+ struct example_state *state = i2c_get_clientdata(client);
+
+ i2c_detach_client(client);
+ kfree(state);
+ return 0;
+}
+
+static int example_attach_adapter(struct i2c_adapter *adap)
+{
+ return i2c_probe(adap, &addr_data, example_attach);
+}
+
+static struct i2c_driver example_driver = {
+ .driver = {
+ .owner = THIS_MODULE,
+ .name = "example",
+ },
+ .attach_adapter = example_attach_adapter,
+ .detach_client = example_detach,
+ .suspend = example_suspend,
+ .resume = example_resume,
+};
+
+
+Updating the client
+-------------------
+
+The new style binding model will check against a list of supported
+devices and their associated address supplied by the code registering
+the busses. This means that the driver .attach_adapter and
+.detach_client methods can be removed, along with the addr_data,
+as follows:
+
+- static struct i2c_driver example_driver;
+
+- static unsigned short ignore[] = { I2C_CLIENT_END };
+- static unsigned short normal_addr[] = { OUR_ADDR, I2C_CLIENT_END };
+
+- I2C_CLIENT_INSMOD;
+
+- static int example_attach_adapter(struct i2c_adapter *adap)
+- {
+- return i2c_probe(adap, &addr_data, example_attach);
+- }
+
+ static struct i2c_driver example_driver = {
+- .attach_adapter = example_attach_adapter,
+- .detach_client = example_detach,
+ }
+
+Add the probe and remove methods to the i2c_driver, as so:
+
+ static struct i2c_driver example_driver = {
++ .probe = example_probe,
++ .remove = example_remove,
+ }
+
+Change the example_attach method to accept the new parameters
+which include the i2c_client that it will be working with:
+
+- static int example_attach(struct i2c_adapter *adap, int addr, int kind)
++ static int example_probe(struct i2c_client *client,
++ const struct i2c_device_id *id)
+
+Change the name of example_attach to example_probe to align it with the
+i2c_driver entry names. The rest of the probe routine will now need to be
+changed as the i2c_client has already been setup for use.
+
+The necessary client fields have already been setup before
+the probe function is called, so the following client setup
+can be removed:
+
+- example->client.addr = addr;
+- example->client.flags = 0;
+- example->client.adapter = adap;
+-
+- strlcpy(client->i2c_client.name, "example", I2C_NAME_SIZE);
+
+The i2c_set_clientdata is now:
+
+- i2c_set_clientdata(&state->client, state);
++ i2c_set_clientdata(client, state);
+
+The call to i2c_attach_client is no longer needed, if the probe
+routine exits successfully, then the driver will be automatically
+attached by the core. Change the probe routine as so:
+
+- ret = i2c_attach_client(&state->i2c_client);
+- if (ret < 0) {
+- dev_err(dev, "failed to attach client\n");
+- kfree(state);
+- return ret;
+- }
+
+
+Remove the storage of 'struct i2c_client' from the 'struct example_state'
+as we are provided with the i2c_client in our example_probe. Instead we
+store a pointer to it for when it is needed.
+
+struct example_state {
+- struct i2c_client client;
++ struct i2c_client *client;
+
+the new i2c client as so:
+
+- struct device *dev = &adap->dev; /* to use for dev_ reports */
++ struct device *dev = &i2c_client->dev; /* to use for dev_ reports */
+
+And remove the change after our client is attached, as the driver no
+longer needs to register a new client structure with the core:
+
+- dev = &state->i2c_client.dev;
+
+In the probe routine, ensure that the new state has the client stored
+in it:
+
+static int example_probe(struct i2c_client *i2c_client,
+ const struct i2c_device_id *id)
+{
+ struct example_state *state;
+ struct device *dev = &i2c_client->dev;
+ int ret;
+
+ state = kzalloc(sizeof(struct example_state), GFP_KERNEL);
+ if (state == NULL) {
+ dev_err(dev, "failed to create our state\n");
+ return -ENOMEM;
+ }
+
++ state->client = i2c_client;
+
+Update the detach method, by changing the name to _remove and
+to delete the i2c_detach_client call. It is possible that you
+can also remove the ret variable as it is not not needed for
+any of the core functions.
+
+- static int example_detach(struct i2c_client *client)
++ static int example_remove(struct i2c_client *client)
+{
+ struct example_state *state = i2c_get_clientdata(client);
+
+- i2c_detach_client(client);
+
+And finally ensure that we have the correct ID table for the i2c-core
+and other utilities:
+
++ struct i2c_device_id example_idtable[] = {
++ { "example", 0 },
++ { }
++};
++
++MODULE_DEVICE_TABLE(i2c, example_idtable);
+
+static struct i2c_driver example_driver = {
+ .driver = {
+ .owner = THIS_MODULE,
+ .name = "example",
+ },
++ .id_table = example_ids,
+
+
+Our driver should now look like this:
+
+struct example_state {
+ struct i2c_client *client;
+ ....
+};
+
+static int example_probe(struct i2c_client *client,
+ const struct i2c_device_id *id)
+{
+ struct example_state *state;
+ struct device *dev = &client->dev;
+
+ state = kzalloc(sizeof(struct example_state), GFP_KERNEL);
+ if (state == NULL) {
+ dev_err(dev, "failed to create our state\n");
+ return -ENOMEM;
+ }
+
+ state->client = client;
+ i2c_set_clientdata(client, state);
+
+ /* rest of the initialisation goes here. */
+
+ dev_info(dev, "example client created\n");
+
+ return 0;
+}
+
+static int example_remove(struct i2c_client *client)
+{
+ struct example_state *state = i2c_get_clientdata(client);
+
+ kfree(state);
+ return 0;
+}
+
+static struct i2c_device_id example_idtable[] = {
+ { "example", 0 },
+ { }
+};
+
+MODULE_DEVICE_TABLE(i2c, example_idtable);
+
+static struct i2c_driver example_driver = {
+ .driver = {
+ .owner = THIS_MODULE,
+ .name = "example",
+ },
+ .id_table = example_idtable,
+ .probe = example_probe,
+ .remove = example_remove,
+ .suspend = example_suspend,
+ .resume = example_resume,
+};