Root/Documentation/i2c/upgrading-clients

1Upgrading I2C Drivers to the new 2.6 Driver Model
2=================================================
3
4Ben Dooks <ben-linux@fluff.org>
5
6Introduction
7------------
8
9This guide outlines how to alter existing Linux 2.6 client drivers from
10the old to the new new binding methods.
11
12
13Example old-style driver
14------------------------
15
16
17struct example_state {
18    struct i2c_client client;
19    ....
20};
21
22static struct i2c_driver example_driver;
23
24static unsigned short ignore[] = { I2C_CLIENT_END };
25static unsigned short normal_addr[] = { OUR_ADDR, I2C_CLIENT_END };
26
27I2C_CLIENT_INSMOD;
28
29static int example_attach(struct i2c_adapter *adap, int addr, int kind)
30{
31    struct example_state *state;
32    struct device *dev = &adap->dev; /* to use for dev_ reports */
33    int ret;
34
35    state = kzalloc(sizeof(struct example_state), GFP_KERNEL);
36    if (state == NULL) {
37        dev_err(dev, "failed to create our state\n");
38        return -ENOMEM;
39    }
40
41    example->client.addr = addr;
42    example->client.flags = 0;
43    example->client.adapter = adap;
44
45    i2c_set_clientdata(&state->i2c_client, state);
46    strlcpy(client->i2c_client.name, "example", I2C_NAME_SIZE);
47
48    ret = i2c_attach_client(&state->i2c_client);
49    if (ret < 0) {
50        dev_err(dev, "failed to attach client\n");
51        kfree(state);
52        return ret;
53    }
54
55    dev = &state->i2c_client.dev;
56
57    /* rest of the initialisation goes here. */
58
59    dev_info(dev, "example client created\n");
60
61    return 0;
62}
63
64static int __devexit example_detach(struct i2c_client *client)
65{
66    struct example_state *state = i2c_get_clientdata(client);
67
68    i2c_detach_client(client);
69    kfree(state);
70    return 0;
71}
72
73static int example_attach_adapter(struct i2c_adapter *adap)
74{
75    return i2c_probe(adap, &addr_data, example_attach);
76}
77
78static struct i2c_driver example_driver = {
79     .driver = {
80        .owner = THIS_MODULE,
81        .name = "example",
82    },
83    .attach_adapter = example_attach_adapter,
84    .detach_client = __devexit_p(example_detach),
85    .suspend = example_suspend,
86    .resume = example_resume,
87};
88
89
90Updating the client
91-------------------
92
93The new style binding model will check against a list of supported
94devices and their associated address supplied by the code registering
95the busses. This means that the driver .attach_adapter and
96.detach_adapter methods can be removed, along with the addr_data,
97as follows:
98
99- static struct i2c_driver example_driver;
100
101- static unsigned short ignore[] = { I2C_CLIENT_END };
102- static unsigned short normal_addr[] = { OUR_ADDR, I2C_CLIENT_END };
103
104- I2C_CLIENT_INSMOD;
105
106- static int example_attach_adapter(struct i2c_adapter *adap)
107- {
108- return i2c_probe(adap, &addr_data, example_attach);
109- }
110
111 static struct i2c_driver example_driver = {
112- .attach_adapter = example_attach_adapter,
113- .detach_client = __devexit_p(example_detach),
114 }
115
116Add the probe and remove methods to the i2c_driver, as so:
117
118 static struct i2c_driver example_driver = {
119+ .probe = example_probe,
120+ .remove = __devexit_p(example_remove),
121 }
122
123Change the example_attach method to accept the new parameters
124which include the i2c_client that it will be working with:
125
126- static int example_attach(struct i2c_adapter *adap, int addr, int kind)
127+ static int example_probe(struct i2c_client *client,
128+ const struct i2c_device_id *id)
129
130Change the name of example_attach to example_probe to align it with the
131i2c_driver entry names. The rest of the probe routine will now need to be
132changed as the i2c_client has already been setup for use.
133
134The necessary client fields have already been setup before
135the probe function is called, so the following client setup
136can be removed:
137
138- example->client.addr = addr;
139- example->client.flags = 0;
140- example->client.adapter = adap;
141-
142- strlcpy(client->i2c_client.name, "example", I2C_NAME_SIZE);
143
144The i2c_set_clientdata is now:
145
146- i2c_set_clientdata(&state->client, state);
147+ i2c_set_clientdata(client, state);
148
149The call to i2c_attach_client is no longer needed, if the probe
150routine exits successfully, then the driver will be automatically
151attached by the core. Change the probe routine as so:
152
153- ret = i2c_attach_client(&state->i2c_client);
154- if (ret < 0) {
155- dev_err(dev, "failed to attach client\n");
156- kfree(state);
157- return ret;
158- }
159
160
161Remove the storage of 'struct i2c_client' from the 'struct example_state'
162as we are provided with the i2c_client in our example_probe. Instead we
163store a pointer to it for when it is needed.
164
165struct example_state {
166- struct i2c_client client;
167+ struct i2c_client *client;
168
169the new i2c client as so:
170
171- struct device *dev = &adap->dev; /* to use for dev_ reports */
172+ struct device *dev = &i2c_client->dev; /* to use for dev_ reports */
173
174And remove the change after our client is attached, as the driver no
175longer needs to register a new client structure with the core:
176
177- dev = &state->i2c_client.dev;
178
179In the probe routine, ensure that the new state has the client stored
180in it:
181
182static int example_probe(struct i2c_client *i2c_client,
183             const struct i2c_device_id *id)
184{
185    struct example_state *state;
186     struct device *dev = &i2c_client->dev;
187    int ret;
188
189    state = kzalloc(sizeof(struct example_state), GFP_KERNEL);
190    if (state == NULL) {
191        dev_err(dev, "failed to create our state\n");
192        return -ENOMEM;
193    }
194
195+ state->client = i2c_client;
196
197Update the detach method, by changing the name to _remove and
198to delete the i2c_detach_client call. It is possible that you
199can also remove the ret variable as it is not not needed for
200any of the core functions.
201
202- static int __devexit example_detach(struct i2c_client *client)
203+ static int __devexit example_remove(struct i2c_client *client)
204{
205    struct example_state *state = i2c_get_clientdata(client);
206
207- i2c_detach_client(client);
208
209And finally ensure that we have the correct ID table for the i2c-core
210and other utilities:
211
212+ struct i2c_device_id example_idtable[] = {
213+ { "example", 0 },
214+ { }
215+};
216+
217+MODULE_DEVICE_TABLE(i2c, example_idtable);
218
219static struct i2c_driver example_driver = {
220     .driver = {
221        .owner = THIS_MODULE,
222        .name = "example",
223    },
224+ .id_table = example_ids,
225
226
227Our driver should now look like this:
228
229struct example_state {
230    struct i2c_client *client;
231    ....
232};
233
234static int example_probe(struct i2c_client *client,
235                  const struct i2c_device_id *id)
236{
237    struct example_state *state;
238    struct device *dev = &client->dev;
239
240    state = kzalloc(sizeof(struct example_state), GFP_KERNEL);
241    if (state == NULL) {
242        dev_err(dev, "failed to create our state\n");
243        return -ENOMEM;
244    }
245
246    state->client = client;
247    i2c_set_clientdata(client, state);
248
249    /* rest of the initialisation goes here. */
250
251    dev_info(dev, "example client created\n");
252
253    return 0;
254}
255
256static int __devexit example_remove(struct i2c_client *client)
257{
258    struct example_state *state = i2c_get_clientdata(client);
259
260    kfree(state);
261    return 0;
262}
263
264static struct i2c_device_id example_idtable[] = {
265    { "example", 0 },
266    { }
267};
268
269MODULE_DEVICE_TABLE(i2c, example_idtable);
270
271static struct i2c_driver example_driver = {
272     .driver = {
273        .owner = THIS_MODULE,
274        .name = "example",
275    },
276    .id_table = example_idtable,
277    .probe = example_probe,
278    .remove = __devexit_p(example_remove),
279    .suspend = example_suspend,
280    .resume = example_resume,
281};
282

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