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Based on kernel version 3.16. Page generated on 2014-08-06 21:39 EST.

1	Upgrading I2C Drivers to the new 2.6 Driver Model
2	=================================================
3	
4	Ben Dooks <ben-linux@fluff.org>
5	
6	Introduction
7	------------
8	
9	This guide outlines how to alter existing Linux 2.6 client drivers from
10	the old to the new new binding methods.
11	
12	
13	Example old-style driver
14	------------------------
15	
16	
17	struct example_state {
18		struct i2c_client	client;
19		....
20	};
21	
22	static struct i2c_driver example_driver;
23	
24	static unsigned short ignore[] = { I2C_CLIENT_END };
25	static unsigned short normal_addr[] = { OUR_ADDR, I2C_CLIENT_END };
26	
27	I2C_CLIENT_INSMOD;
28	
29	static 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	
64	static int 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	
73	static int example_attach_adapter(struct i2c_adapter *adap)
74	{
75		return i2c_probe(adap, &addr_data, example_attach);
76	}
77	
78	static struct i2c_driver example_driver = {
79	 	.driver		= {
80			.owner		= THIS_MODULE,
81			.name		= "example",
82		},
83		.attach_adapter = example_attach_adapter,
84		.detach_client	= example_detach,
85		.suspend	= example_suspend,
86		.resume		= example_resume,
87	};
88	
89	
90	Updating the client
91	-------------------
92	
93	The new style binding model will check against a list of supported
94	devices and their associated address supplied by the code registering
95	the busses. This means that the driver .attach_adapter and
96	.detach_client methods can be removed, along with the addr_data,
97	as 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	= example_detach,
114	 }
115	
116	Add 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		= example_remove,
121	 }
122	
123	Change the example_attach method to accept the new parameters
124	which 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	
130	Change the name of example_attach to example_probe to align it with the
131	i2c_driver entry names. The rest of the probe routine will now need to be
132	changed as the i2c_client has already been setup for use.
133	
134	The necessary client fields have already been setup before
135	the probe function is called, so the following client setup
136	can 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	
144	The i2c_set_clientdata is now:
145	
146	-	i2c_set_clientdata(&state->client, state);
147	+	i2c_set_clientdata(client, state);
148	
149	The call to i2c_attach_client is no longer needed, if the probe
150	routine exits successfully, then the driver will be automatically
151	attached 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	
161	Remove the storage of 'struct i2c_client' from the 'struct example_state'
162	as we are provided with the i2c_client in our example_probe. Instead we
163	store a pointer to it for when it is needed.
164	
165	struct example_state {
166	-	struct i2c_client	client;
167	+	struct i2c_client	*client;
168	
169	the 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	
174	And remove the change after our client is attached, as the driver no
175	longer needs to register a new client structure with the core:
176	
177	-	dev = &state->i2c_client.dev;
178	
179	In the probe routine, ensure that the new state has the client stored
180	in it:
181	
182	static 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	
197	Update the detach method, by changing the name to _remove and
198	to delete the i2c_detach_client call. It is possible that you
199	can also remove the ret variable as it is not needed for any
200	of the core functions.
201	
202	- static int example_detach(struct i2c_client *client)
203	+ static int example_remove(struct i2c_client *client)
204	{
205		struct example_state *state = i2c_get_clientdata(client);
206	
207	-	i2c_detach_client(client);
208	
209	And finally ensure that we have the correct ID table for the i2c-core
210	and other utilities:
211	
212	+ struct i2c_device_id example_idtable[] = {
213	+       { "example", 0 },
214	+       { }
215	+};
216	+
217	+MODULE_DEVICE_TABLE(i2c, example_idtable);
218	
219	static struct i2c_driver example_driver = {
220	 	.driver		= {
221			.owner		= THIS_MODULE,
222			.name		= "example",
223		},
224	+	.id_table	= example_ids,
225	
226	
227	Our driver should now look like this:
228	
229	struct example_state {
230		struct i2c_client	*client;
231		....
232	};
233	
234	static 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	
256	static int 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	
264	static struct i2c_device_id example_idtable[] = {
265		{ "example", 0 },
266		{ }
267	};
268	
269	MODULE_DEVICE_TABLE(i2c, example_idtable);
270	
271	static 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		= example_remove,
279		.suspend	= example_suspend,
280		.resume		= example_resume,
281	};
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