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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,
-};