I would like to get people's opinions on adding
the following as Documentation/i2c/upgrading-clients.
Upgrading I2C Drivers to the new 2.6 Driver Model
=================================================
Ben Dooks <[EMAIL PROTECTED]>
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 };
static struct i2c_client_address_data addr_data = {
.normal_i2c = normal_addr,
.probe = ignore,
.ignore = ignore,
};
static int example_attach(struct i2c_adapter *adap, int addr, int kind)
{
struct example_state *state;
struct device *dev = &adap->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;
}
example->i2c_client.addr = addr;
example->i2c_client.flags = 0;
example->i2c_client.adapter = adap;
i2c_set_clientdata(&state->i2c_client, state);
strlcpy(client->i2c_client.name, example_driver.driver.name,
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. */
return 0;
}
static int example_remove(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_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 };
- static struct i2c_client_address_data addr_data = {
- .normal_i2c = normal_addr,
- .probe = ignore,
- .ignore = ignore,
- };
- 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 = simtec_pmu_probe,
+ .remove = simtec_pmu_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 *i2c_client,
+ const struct i2c_device_id *id)
Note, we 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.
Remove the setting of address and adapter, they are now not needed.
- example->i2c_client.addr = addr;
- example->i2c_client.flags = 0;
- example->i2c_client.adapter = adap;
Also remove the strlcpy, as the i2c_client's name is already filled
in by the caller.
- strlcpy(client->i2c_client.name, example_driver.driver.name,
- I2C_NAME_SIZE);
The call to i2c_attach_client is no longer needed, if the probe
routine exits succssfully, then the driver has been attached. 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;
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 = &adap->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 remove method to delete the i2c_detach_client call.
static int example_remove(struct i2c_client *client)
{
struct example_state *state = i2c_get_clientdata(client);
- i2c_detach_client(client);
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