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 __devexit 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 = __devexit_p(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_adapter 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 = __devexit_p(example_detach),
}
Add the probe and remove methods to the i2c_driver, as so:
static struct i2c_driver example_driver = {
+ .probe = example_probe,
+ .remove = __devexit_p(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 __devexit example_detach(struct i2c_client *client)
+ static int __devexit 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 __devexit 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 = __devexit_p(example_remove),
.suspend = example_suspend,
.resume = example_resume,
};
