Commit | Line | Data |
---|---|---|
1da177e4 | 1 | This is a small guide for those who want to write kernel drivers for I2C |
4298cfc3 | 2 | or SMBus devices, using Linux as the protocol host/master (not slave). |
1da177e4 LT |
3 | |
4 | To set up a driver, you need to do several things. Some are optional, and | |
5 | some things can be done slightly or completely different. Use this as a | |
6 | guide, not as a rule book! | |
7 | ||
8 | ||
9 | General remarks | |
10 | =============== | |
11 | ||
12 | Try to keep the kernel namespace as clean as possible. The best way to | |
13 | do this is to use a unique prefix for all global symbols. This is | |
14 | especially important for exported symbols, but it is a good idea to do | |
15 | it for non-exported symbols too. We will use the prefix `foo_' in this | |
16 | tutorial, and `FOO_' for preprocessor variables. | |
17 | ||
18 | ||
19 | The driver structure | |
20 | ==================== | |
21 | ||
22 | Usually, you will implement a single driver structure, and instantiate | |
23 | all clients from it. Remember, a driver structure contains general access | |
f37dd80a DB |
24 | routines, and should be zero-initialized except for fields with data you |
25 | provide. A client structure holds device-specific information like the | |
26 | driver model device node, and its I2C address. | |
1da177e4 LT |
27 | |
28 | static struct i2c_driver foo_driver = { | |
d45d204f | 29 | .driver = { |
d45d204f JD |
30 | .name = "foo", |
31 | }, | |
4298cfc3 DB |
32 | |
33 | /* iff driver uses driver model ("new style") binding model: */ | |
34 | .probe = foo_probe, | |
35 | .remove = foo_remove, | |
36 | ||
37 | /* else, driver uses "legacy" binding model: */ | |
f37dd80a DB |
38 | .attach_adapter = foo_attach_adapter, |
39 | .detach_client = foo_detach_client, | |
4298cfc3 DB |
40 | |
41 | /* these may be used regardless of the driver binding model */ | |
f37dd80a DB |
42 | .shutdown = foo_shutdown, /* optional */ |
43 | .suspend = foo_suspend, /* optional */ | |
44 | .resume = foo_resume, /* optional */ | |
45 | .command = foo_command, /* optional */ | |
1da177e4 LT |
46 | } |
47 | ||
f37dd80a DB |
48 | The name field is the driver name, and must not contain spaces. It |
49 | should match the module name (if the driver can be compiled as a module), | |
50 | although you can use MODULE_ALIAS (passing "foo" in this example) to add | |
4298cfc3 DB |
51 | another name for the module. If the driver name doesn't match the module |
52 | name, the module won't be automatically loaded (hotplug/coldplug). | |
1da177e4 | 53 | |
1da177e4 LT |
54 | All other fields are for call-back functions which will be explained |
55 | below. | |
56 | ||
1da177e4 LT |
57 | |
58 | Extra client data | |
59 | ================= | |
60 | ||
f37dd80a DB |
61 | Each client structure has a special `data' field that can point to any |
62 | structure at all. You should use this to keep device-specific data, | |
63 | especially in drivers that handle multiple I2C or SMBUS devices. You | |
1da177e4 LT |
64 | do not always need this, but especially for `sensors' drivers, it can |
65 | be very useful. | |
66 | ||
f37dd80a DB |
67 | /* store the value */ |
68 | void i2c_set_clientdata(struct i2c_client *client, void *data); | |
69 | ||
70 | /* retrieve the value */ | |
71 | void *i2c_get_clientdata(struct i2c_client *client); | |
72 | ||
1da177e4 LT |
73 | An example structure is below. |
74 | ||
75 | struct foo_data { | |
2445eb62 | 76 | struct i2c_client client; |
1da177e4 LT |
77 | struct semaphore lock; /* For ISA access in `sensors' drivers. */ |
78 | int sysctl_id; /* To keep the /proc directory entry for | |
79 | `sensors' drivers. */ | |
80 | enum chips type; /* To keep the chips type for `sensors' drivers. */ | |
81 | ||
82 | /* Because the i2c bus is slow, it is often useful to cache the read | |
83 | information of a chip for some time (for example, 1 or 2 seconds). | |
84 | It depends of course on the device whether this is really worthwhile | |
85 | or even sensible. */ | |
86 | struct semaphore update_lock; /* When we are reading lots of information, | |
87 | another process should not update the | |
88 | below information */ | |
89 | char valid; /* != 0 if the following fields are valid. */ | |
90 | unsigned long last_updated; /* In jiffies */ | |
91 | /* Add the read information here too */ | |
92 | }; | |
93 | ||
94 | ||
95 | Accessing the client | |
96 | ==================== | |
97 | ||
98 | Let's say we have a valid client structure. At some time, we will need | |
99 | to gather information from the client, or write new information to the | |
100 | client. How we will export this information to user-space is less | |
101 | important at this moment (perhaps we do not need to do this at all for | |
102 | some obscure clients). But we need generic reading and writing routines. | |
103 | ||
104 | I have found it useful to define foo_read and foo_write function for this. | |
105 | For some cases, it will be easier to call the i2c functions directly, | |
106 | but many chips have some kind of register-value idea that can easily | |
107 | be encapsulated. Also, some chips have both ISA and I2C interfaces, and | |
108 | it useful to abstract from this (only for `sensors' drivers). | |
109 | ||
110 | The below functions are simple examples, and should not be copied | |
111 | literally. | |
112 | ||
113 | int foo_read_value(struct i2c_client *client, u8 reg) | |
114 | { | |
115 | if (reg < 0x10) /* byte-sized register */ | |
116 | return i2c_smbus_read_byte_data(client,reg); | |
117 | else /* word-sized register */ | |
118 | return i2c_smbus_read_word_data(client,reg); | |
119 | } | |
120 | ||
121 | int foo_write_value(struct i2c_client *client, u8 reg, u16 value) | |
122 | { | |
123 | if (reg == 0x10) /* Impossible to write - driver error! */ { | |
124 | return -1; | |
125 | else if (reg < 0x10) /* byte-sized register */ | |
126 | return i2c_smbus_write_byte_data(client,reg,value); | |
127 | else /* word-sized register */ | |
128 | return i2c_smbus_write_word_data(client,reg,value); | |
129 | } | |
130 | ||
131 | For sensors code, you may have to cope with ISA registers too. Something | |
132 | like the below often works. Note the locking! | |
133 | ||
134 | int foo_read_value(struct i2c_client *client, u8 reg) | |
135 | { | |
136 | int res; | |
137 | if (i2c_is_isa_client(client)) { | |
138 | down(&(((struct foo_data *) (client->data)) -> lock)); | |
139 | outb_p(reg,client->addr + FOO_ADDR_REG_OFFSET); | |
140 | res = inb_p(client->addr + FOO_DATA_REG_OFFSET); | |
141 | up(&(((struct foo_data *) (client->data)) -> lock)); | |
142 | return res; | |
143 | } else | |
144 | return i2c_smbus_read_byte_data(client,reg); | |
145 | } | |
146 | ||
147 | Writing is done the same way. | |
148 | ||
149 | ||
150 | Probing and attaching | |
151 | ===================== | |
152 | ||
4298cfc3 DB |
153 | The Linux I2C stack was originally written to support access to hardware |
154 | monitoring chips on PC motherboards, and thus it embeds some assumptions | |
155 | that are more appropriate to SMBus (and PCs) than to I2C. One of these | |
156 | assumptions is that most adapters and devices drivers support the SMBUS_QUICK | |
157 | protocol to probe device presence. Another is that devices and their drivers | |
158 | can be sufficiently configured using only such probe primitives. | |
159 | ||
160 | As Linux and its I2C stack became more widely used in embedded systems | |
161 | and complex components such as DVB adapters, those assumptions became more | |
162 | problematic. Drivers for I2C devices that issue interrupts need more (and | |
163 | different) configuration information, as do drivers handling chip variants | |
164 | that can't be distinguished by protocol probing, or which need some board | |
165 | specific information to operate correctly. | |
166 | ||
167 | Accordingly, the I2C stack now has two models for associating I2C devices | |
168 | with their drivers: the original "legacy" model, and a newer one that's | |
169 | fully compatible with the Linux 2.6 driver model. These models do not mix, | |
170 | since the "legacy" model requires drivers to create "i2c_client" device | |
171 | objects after SMBus style probing, while the Linux driver model expects | |
172 | drivers to be given such device objects in their probe() routines. | |
173 | ||
174 | ||
175 | Standard Driver Model Binding ("New Style") | |
176 | ------------------------------------------- | |
177 | ||
178 | System infrastructure, typically board-specific initialization code or | |
179 | boot firmware, reports what I2C devices exist. For example, there may be | |
180 | a table, in the kernel or from the boot loader, identifying I2C devices | |
181 | and linking them to board-specific configuration information about IRQs | |
182 | and other wiring artifacts, chip type, and so on. That could be used to | |
183 | create i2c_client objects for each I2C device. | |
184 | ||
185 | I2C device drivers using this binding model work just like any other | |
186 | kind of driver in Linux: they provide a probe() method to bind to | |
187 | those devices, and a remove() method to unbind. | |
188 | ||
189 | static int foo_probe(struct i2c_client *client); | |
190 | static int foo_remove(struct i2c_client *client); | |
191 | ||
192 | Remember that the i2c_driver does not create those client handles. The | |
193 | handle may be used during foo_probe(). If foo_probe() reports success | |
194 | (zero not a negative status code) it may save the handle and use it until | |
195 | foo_remove() returns. That binding model is used by most Linux drivers. | |
196 | ||
197 | Drivers match devices when i2c_client.driver_name and the driver name are | |
198 | the same; this approach is used in several other busses that don't have | |
199 | device typing support in the hardware. The driver and module name should | |
200 | match, so hotplug/coldplug mechanisms will modprobe the driver. | |
201 | ||
202 | ||
ce9e0794 JD |
203 | Device Creation (Standard driver model) |
204 | --------------------------------------- | |
205 | ||
206 | If you know for a fact that an I2C device is connected to a given I2C bus, | |
207 | you can instantiate that device by simply filling an i2c_board_info | |
208 | structure with the device address and driver name, and calling | |
209 | i2c_new_device(). This will create the device, then the driver core will | |
210 | take care of finding the right driver and will call its probe() method. | |
211 | If a driver supports different device types, you can specify the type you | |
212 | want using the type field. You can also specify an IRQ and platform data | |
213 | if needed. | |
214 | ||
215 | Sometimes you know that a device is connected to a given I2C bus, but you | |
216 | don't know the exact address it uses. This happens on TV adapters for | |
217 | example, where the same driver supports dozens of slightly different | |
218 | models, and I2C device addresses change from one model to the next. In | |
219 | that case, you can use the i2c_new_probed_device() variant, which is | |
220 | similar to i2c_new_device(), except that it takes an additional list of | |
221 | possible I2C addresses to probe. A device is created for the first | |
222 | responsive address in the list. If you expect more than one device to be | |
223 | present in the address range, simply call i2c_new_probed_device() that | |
224 | many times. | |
225 | ||
226 | The call to i2c_new_device() or i2c_new_probed_device() typically happens | |
227 | in the I2C bus driver. You may want to save the returned i2c_client | |
228 | reference for later use. | |
229 | ||
230 | ||
231 | Device Deletion (Standard driver model) | |
232 | --------------------------------------- | |
233 | ||
234 | Each I2C device which has been created using i2c_new_device() or | |
235 | i2c_new_probed_device() can be unregistered by calling | |
236 | i2c_unregister_device(). If you don't call it explicitly, it will be | |
237 | called automatically before the underlying I2C bus itself is removed, as a | |
238 | device can't survive its parent in the device driver model. | |
239 | ||
240 | ||
4298cfc3 DB |
241 | Legacy Driver Binding Model |
242 | --------------------------- | |
243 | ||
1da177e4 LT |
244 | Most i2c devices can be present on several i2c addresses; for some this |
245 | is determined in hardware (by soldering some chip pins to Vcc or Ground), | |
246 | for others this can be changed in software (by writing to specific client | |
247 | registers). Some devices are usually on a specific address, but not always; | |
248 | and some are even more tricky. So you will probably need to scan several | |
249 | i2c addresses for your clients, and do some sort of detection to see | |
250 | whether it is actually a device supported by your driver. | |
251 | ||
252 | To give the user a maximum of possibilities, some default module parameters | |
253 | are defined to help determine what addresses are scanned. Several macros | |
254 | are defined in i2c.h to help you support them, as well as a generic | |
255 | detection algorithm. | |
256 | ||
257 | You do not have to use this parameter interface; but don't try to use | |
2ed2dc3c | 258 | function i2c_probe() if you don't. |
1da177e4 LT |
259 | |
260 | NOTE: If you want to write a `sensors' driver, the interface is slightly | |
261 | different! See below. | |
262 | ||
263 | ||
264 | ||
4298cfc3 DB |
265 | Probing classes (Legacy model) |
266 | ------------------------------ | |
1da177e4 LT |
267 | |
268 | All parameters are given as lists of unsigned 16-bit integers. Lists are | |
269 | terminated by I2C_CLIENT_END. | |
270 | The following lists are used internally: | |
271 | ||
272 | normal_i2c: filled in by the module writer. | |
273 | A list of I2C addresses which should normally be examined. | |
1da177e4 LT |
274 | probe: insmod parameter. |
275 | A list of pairs. The first value is a bus number (-1 for any I2C bus), | |
276 | the second is the address. These addresses are also probed, as if they | |
277 | were in the 'normal' list. | |
1da177e4 LT |
278 | ignore: insmod parameter. |
279 | A list of pairs. The first value is a bus number (-1 for any I2C bus), | |
280 | the second is the I2C address. These addresses are never probed. | |
f4b50261 | 281 | This parameter overrules the 'normal_i2c' list only. |
1da177e4 LT |
282 | force: insmod parameter. |
283 | A list of pairs. The first value is a bus number (-1 for any I2C bus), | |
284 | the second is the I2C address. A device is blindly assumed to be on | |
285 | the given address, no probing is done. | |
286 | ||
f4b50261 JD |
287 | Additionally, kind-specific force lists may optionally be defined if |
288 | the driver supports several chip kinds. They are grouped in a | |
289 | NULL-terminated list of pointers named forces, those first element if the | |
290 | generic force list mentioned above. Each additional list correspond to an | |
291 | insmod parameter of the form force_<kind>. | |
292 | ||
b3d5496e JD |
293 | Fortunately, as a module writer, you just have to define the `normal_i2c' |
294 | parameter. The complete declaration could look like this: | |
1da177e4 | 295 | |
b3d5496e JD |
296 | /* Scan 0x37, and 0x48 to 0x4f */ |
297 | static unsigned short normal_i2c[] = { 0x37, 0x48, 0x49, 0x4a, 0x4b, 0x4c, | |
298 | 0x4d, 0x4e, 0x4f, I2C_CLIENT_END }; | |
1da177e4 LT |
299 | |
300 | /* Magic definition of all other variables and things */ | |
301 | I2C_CLIENT_INSMOD; | |
f4b50261 JD |
302 | /* Or, if your driver supports, say, 2 kind of devices: */ |
303 | I2C_CLIENT_INSMOD_2(foo, bar); | |
304 | ||
305 | If you use the multi-kind form, an enum will be defined for you: | |
306 | enum chips { any_chip, foo, bar, ... } | |
307 | You can then (and certainly should) use it in the driver code. | |
1da177e4 | 308 | |
b3d5496e JD |
309 | Note that you *have* to call the defined variable `normal_i2c', |
310 | without any prefix! | |
1da177e4 LT |
311 | |
312 | ||
4298cfc3 DB |
313 | Attaching to an adapter (Legacy model) |
314 | -------------------------------------- | |
1da177e4 LT |
315 | |
316 | Whenever a new adapter is inserted, or for all adapters if the driver is | |
317 | being registered, the callback attach_adapter() is called. Now is the | |
318 | time to determine what devices are present on the adapter, and to register | |
319 | a client for each of them. | |
320 | ||
321 | The attach_adapter callback is really easy: we just call the generic | |
322 | detection function. This function will scan the bus for us, using the | |
323 | information as defined in the lists explained above. If a device is | |
324 | detected at a specific address, another callback is called. | |
325 | ||
326 | int foo_attach_adapter(struct i2c_adapter *adapter) | |
327 | { | |
328 | return i2c_probe(adapter,&addr_data,&foo_detect_client); | |
329 | } | |
330 | ||
1da177e4 LT |
331 | Remember, structure `addr_data' is defined by the macros explained above, |
332 | so you do not have to define it yourself. | |
333 | ||
2ed2dc3c | 334 | The i2c_probe function will call the foo_detect_client |
1da177e4 LT |
335 | function only for those i2c addresses that actually have a device on |
336 | them (unless a `force' parameter was used). In addition, addresses that | |
337 | are already in use (by some other registered client) are skipped. | |
338 | ||
339 | ||
4298cfc3 DB |
340 | The detect client function (Legacy model) |
341 | ----------------------------------------- | |
1da177e4 | 342 | |
2ed2dc3c JD |
343 | The detect client function is called by i2c_probe. The `kind' parameter |
344 | contains -1 for a probed detection, 0 for a forced detection, or a positive | |
345 | number for a forced detection with a chip type forced. | |
1da177e4 LT |
346 | |
347 | Below, some things are only needed if this is a `sensors' driver. Those | |
348 | parts are between /* SENSORS ONLY START */ and /* SENSORS ONLY END */ | |
349 | markers. | |
350 | ||
a89ba0bc JD |
351 | Returning an error different from -ENODEV in a detect function will cause |
352 | the detection to stop: other addresses and adapters won't be scanned. | |
353 | This should only be done on fatal or internal errors, such as a memory | |
354 | shortage or i2c_attach_client failing. | |
1da177e4 LT |
355 | |
356 | For now, you can ignore the `flags' parameter. It is there for future use. | |
357 | ||
358 | int foo_detect_client(struct i2c_adapter *adapter, int address, | |
359 | unsigned short flags, int kind) | |
360 | { | |
361 | int err = 0; | |
362 | int i; | |
363 | struct i2c_client *new_client; | |
364 | struct foo_data *data; | |
365 | const char *client_name = ""; /* For non-`sensors' drivers, put the real | |
366 | name here! */ | |
367 | ||
368 | /* Let's see whether this adapter can support what we need. | |
369 | Please substitute the things you need here! | |
370 | For `sensors' drivers, add `! is_isa &&' to the if statement */ | |
371 | if (!i2c_check_functionality(adapter,I2C_FUNC_SMBUS_WORD_DATA | | |
372 | I2C_FUNC_SMBUS_WRITE_BYTE)) | |
373 | goto ERROR0; | |
374 | ||
375 | /* SENSORS ONLY START */ | |
376 | const char *type_name = ""; | |
377 | int is_isa = i2c_is_isa_adapter(adapter); | |
378 | ||
02ff982c JD |
379 | /* Do this only if the chip can additionally be found on the ISA bus |
380 | (hybrid chip). */ | |
1da177e4 | 381 | |
02ff982c | 382 | if (is_isa) { |
1da177e4 LT |
383 | |
384 | /* Discard immediately if this ISA range is already used */ | |
d61780c0 | 385 | /* FIXME: never use check_region(), only request_region() */ |
1da177e4 LT |
386 | if (check_region(address,FOO_EXTENT)) |
387 | goto ERROR0; | |
388 | ||
389 | /* Probe whether there is anything on this address. | |
390 | Some example code is below, but you will have to adapt this | |
391 | for your own driver */ | |
392 | ||
393 | if (kind < 0) /* Only if no force parameter was used */ { | |
394 | /* We may need long timeouts at least for some chips. */ | |
395 | #define REALLY_SLOW_IO | |
396 | i = inb_p(address + 1); | |
397 | if (inb_p(address + 2) != i) | |
398 | goto ERROR0; | |
399 | if (inb_p(address + 3) != i) | |
400 | goto ERROR0; | |
401 | if (inb_p(address + 7) != i) | |
402 | goto ERROR0; | |
403 | #undef REALLY_SLOW_IO | |
404 | ||
405 | /* Let's just hope nothing breaks here */ | |
406 | i = inb_p(address + 5) & 0x7f; | |
407 | outb_p(~i & 0x7f,address+5); | |
408 | if ((inb_p(address + 5) & 0x7f) != (~i & 0x7f)) { | |
409 | outb_p(i,address+5); | |
410 | return 0; | |
411 | } | |
412 | } | |
413 | } | |
414 | ||
415 | /* SENSORS ONLY END */ | |
416 | ||
417 | /* OK. For now, we presume we have a valid client. We now create the | |
418 | client structure, even though we cannot fill it completely yet. | |
419 | But it allows us to access several i2c functions safely */ | |
420 | ||
2445eb62 | 421 | if (!(data = kzalloc(sizeof(struct foo_data), GFP_KERNEL))) { |
1da177e4 LT |
422 | err = -ENOMEM; |
423 | goto ERROR0; | |
424 | } | |
425 | ||
2445eb62 JD |
426 | new_client = &data->client; |
427 | i2c_set_clientdata(new_client, data); | |
1da177e4 LT |
428 | |
429 | new_client->addr = address; | |
1da177e4 LT |
430 | new_client->adapter = adapter; |
431 | new_client->driver = &foo_driver; | |
432 | new_client->flags = 0; | |
433 | ||
434 | /* Now, we do the remaining detection. If no `force' parameter is used. */ | |
435 | ||
436 | /* First, the generic detection (if any), that is skipped if any force | |
437 | parameter was used. */ | |
438 | if (kind < 0) { | |
439 | /* The below is of course bogus */ | |
440 | if (foo_read(new_client,FOO_REG_GENERIC) != FOO_GENERIC_VALUE) | |
441 | goto ERROR1; | |
442 | } | |
443 | ||
444 | /* SENSORS ONLY START */ | |
445 | ||
446 | /* Next, specific detection. This is especially important for `sensors' | |
447 | devices. */ | |
448 | ||
449 | /* Determine the chip type. Not needed if a `force_CHIPTYPE' parameter | |
450 | was used. */ | |
451 | if (kind <= 0) { | |
452 | i = foo_read(new_client,FOO_REG_CHIPTYPE); | |
453 | if (i == FOO_TYPE_1) | |
454 | kind = chip1; /* As defined in the enum */ | |
455 | else if (i == FOO_TYPE_2) | |
456 | kind = chip2; | |
457 | else { | |
458 | printk("foo: Ignoring 'force' parameter for unknown chip at " | |
459 | "adapter %d, address 0x%02x\n",i2c_adapter_id(adapter),address); | |
460 | goto ERROR1; | |
461 | } | |
462 | } | |
463 | ||
464 | /* Now set the type and chip names */ | |
465 | if (kind == chip1) { | |
466 | type_name = "chip1"; /* For /proc entry */ | |
467 | client_name = "CHIP 1"; | |
468 | } else if (kind == chip2) { | |
469 | type_name = "chip2"; /* For /proc entry */ | |
470 | client_name = "CHIP 2"; | |
471 | } | |
472 | ||
473 | /* Reserve the ISA region */ | |
474 | if (is_isa) | |
475 | request_region(address,FOO_EXTENT,type_name); | |
476 | ||
477 | /* SENSORS ONLY END */ | |
478 | ||
479 | /* Fill in the remaining client fields. */ | |
480 | strcpy(new_client->name,client_name); | |
481 | ||
482 | /* SENSORS ONLY BEGIN */ | |
483 | data->type = kind; | |
484 | /* SENSORS ONLY END */ | |
485 | ||
486 | data->valid = 0; /* Only if you use this field */ | |
487 | init_MUTEX(&data->update_lock); /* Only if you use this field */ | |
488 | ||
489 | /* Any other initializations in data must be done here too. */ | |
490 | ||
491 | /* Tell the i2c layer a new client has arrived */ | |
492 | if ((err = i2c_attach_client(new_client))) | |
493 | goto ERROR3; | |
494 | ||
495 | /* SENSORS ONLY BEGIN */ | |
496 | /* Register a new directory entry with module sensors. See below for | |
497 | the `template' structure. */ | |
498 | if ((i = i2c_register_entry(new_client, type_name, | |
499 | foo_dir_table_template,THIS_MODULE)) < 0) { | |
500 | err = i; | |
501 | goto ERROR4; | |
502 | } | |
503 | data->sysctl_id = i; | |
504 | ||
505 | /* SENSORS ONLY END */ | |
506 | ||
507 | /* This function can write default values to the client registers, if | |
508 | needed. */ | |
509 | foo_init_client(new_client); | |
510 | return 0; | |
511 | ||
512 | /* OK, this is not exactly good programming practice, usually. But it is | |
513 | very code-efficient in this case. */ | |
514 | ||
515 | ERROR4: | |
516 | i2c_detach_client(new_client); | |
517 | ERROR3: | |
518 | ERROR2: | |
519 | /* SENSORS ONLY START */ | |
520 | if (is_isa) | |
521 | release_region(address,FOO_EXTENT); | |
522 | /* SENSORS ONLY END */ | |
523 | ERROR1: | |
a852daa0 | 524 | kfree(data); |
1da177e4 LT |
525 | ERROR0: |
526 | return err; | |
527 | } | |
528 | ||
529 | ||
4298cfc3 DB |
530 | Removing the client (Legacy model) |
531 | ================================== | |
1da177e4 LT |
532 | |
533 | The detach_client call back function is called when a client should be | |
534 | removed. It may actually fail, but only when panicking. This code is | |
535 | much simpler than the attachment code, fortunately! | |
536 | ||
537 | int foo_detach_client(struct i2c_client *client) | |
538 | { | |
539 | int err,i; | |
540 | ||
541 | /* SENSORS ONLY START */ | |
542 | /* Deregister with the `i2c-proc' module. */ | |
543 | i2c_deregister_entry(((struct lm78_data *)(client->data))->sysctl_id); | |
544 | /* SENSORS ONLY END */ | |
545 | ||
546 | /* Try to detach the client from i2c space */ | |
7bef5594 | 547 | if ((err = i2c_detach_client(client))) |
1da177e4 | 548 | return err; |
1da177e4 | 549 | |
02ff982c | 550 | /* HYBRID SENSORS CHIP ONLY START */ |
1da177e4 LT |
551 | if i2c_is_isa_client(client) |
552 | release_region(client->addr,LM78_EXTENT); | |
02ff982c | 553 | /* HYBRID SENSORS CHIP ONLY END */ |
1da177e4 | 554 | |
a852daa0 | 555 | kfree(i2c_get_clientdata(client)); |
1da177e4 LT |
556 | return 0; |
557 | } | |
558 | ||
559 | ||
560 | Initializing the module or kernel | |
561 | ================================= | |
562 | ||
563 | When the kernel is booted, or when your foo driver module is inserted, | |
564 | you have to do some initializing. Fortunately, just attaching (registering) | |
565 | the driver module is usually enough. | |
566 | ||
567 | /* Keep track of how far we got in the initialization process. If several | |
568 | things have to initialized, and we fail halfway, only those things | |
569 | have to be cleaned up! */ | |
570 | static int __initdata foo_initialized = 0; | |
571 | ||
572 | static int __init foo_init(void) | |
573 | { | |
574 | int res; | |
575 | printk("foo version %s (%s)\n",FOO_VERSION,FOO_DATE); | |
576 | ||
577 | if ((res = i2c_add_driver(&foo_driver))) { | |
578 | printk("foo: Driver registration failed, module not inserted.\n"); | |
579 | foo_cleanup(); | |
580 | return res; | |
581 | } | |
582 | foo_initialized ++; | |
583 | return 0; | |
584 | } | |
585 | ||
586 | void foo_cleanup(void) | |
587 | { | |
588 | if (foo_initialized == 1) { | |
b3e82096 | 589 | i2c_del_driver(&foo_driver); |
1da177e4 LT |
590 | foo_initialized --; |
591 | } | |
592 | } | |
593 | ||
594 | /* Substitute your own name and email address */ | |
595 | MODULE_AUTHOR("Frodo Looijaard <frodol@dds.nl>" | |
596 | MODULE_DESCRIPTION("Driver for Barf Inc. Foo I2C devices"); | |
597 | ||
598 | module_init(foo_init); | |
599 | module_exit(foo_cleanup); | |
600 | ||
601 | Note that some functions are marked by `__init', and some data structures | |
602 | by `__init_data'. Hose functions and structures can be removed after | |
603 | kernel booting (or module loading) is completed. | |
604 | ||
fb687d73 | 605 | |
f37dd80a DB |
606 | Power Management |
607 | ================ | |
608 | ||
609 | If your I2C device needs special handling when entering a system low | |
610 | power state -- like putting a transceiver into a low power mode, or | |
611 | activating a system wakeup mechanism -- do that in the suspend() method. | |
612 | The resume() method should reverse what the suspend() method does. | |
613 | ||
614 | These are standard driver model calls, and they work just like they | |
615 | would for any other driver stack. The calls can sleep, and can use | |
616 | I2C messaging to the device being suspended or resumed (since their | |
617 | parent I2C adapter is active when these calls are issued, and IRQs | |
618 | are still enabled). | |
619 | ||
620 | ||
621 | System Shutdown | |
622 | =============== | |
623 | ||
624 | If your I2C device needs special handling when the system shuts down | |
625 | or reboots (including kexec) -- like turning something off -- use a | |
626 | shutdown() method. | |
627 | ||
628 | Again, this is a standard driver model call, working just like it | |
629 | would for any other driver stack: the calls can sleep, and can use | |
630 | I2C messaging. | |
631 | ||
632 | ||
1da177e4 LT |
633 | Command function |
634 | ================ | |
635 | ||
636 | A generic ioctl-like function call back is supported. You will seldom | |
fb687d73 JD |
637 | need this, and its use is deprecated anyway, so newer design should not |
638 | use it. Set it to NULL. | |
1da177e4 LT |
639 | |
640 | ||
641 | Sending and receiving | |
642 | ===================== | |
643 | ||
644 | If you want to communicate with your device, there are several functions | |
645 | to do this. You can find all of them in i2c.h. | |
646 | ||
647 | If you can choose between plain i2c communication and SMBus level | |
648 | communication, please use the last. All adapters understand SMBus level | |
649 | commands, but only some of them understand plain i2c! | |
650 | ||
651 | ||
652 | Plain i2c communication | |
653 | ----------------------- | |
654 | ||
655 | extern int i2c_master_send(struct i2c_client *,const char* ,int); | |
656 | extern int i2c_master_recv(struct i2c_client *,char* ,int); | |
657 | ||
658 | These routines read and write some bytes from/to a client. The client | |
659 | contains the i2c address, so you do not have to include it. The second | |
660 | parameter contains the bytes the read/write, the third the length of the | |
661 | buffer. Returned is the actual number of bytes read/written. | |
662 | ||
663 | extern int i2c_transfer(struct i2c_adapter *adap, struct i2c_msg *msg, | |
664 | int num); | |
665 | ||
666 | This sends a series of messages. Each message can be a read or write, | |
667 | and they can be mixed in any way. The transactions are combined: no | |
668 | stop bit is sent between transaction. The i2c_msg structure contains | |
669 | for each message the client address, the number of bytes of the message | |
670 | and the message data itself. | |
671 | ||
672 | You can read the file `i2c-protocol' for more information about the | |
673 | actual i2c protocol. | |
674 | ||
675 | ||
676 | SMBus communication | |
677 | ------------------- | |
678 | ||
679 | extern s32 i2c_smbus_xfer (struct i2c_adapter * adapter, u16 addr, | |
680 | unsigned short flags, | |
681 | char read_write, u8 command, int size, | |
682 | union i2c_smbus_data * data); | |
683 | ||
684 | This is the generic SMBus function. All functions below are implemented | |
685 | in terms of it. Never use this function directly! | |
686 | ||
687 | ||
688 | extern s32 i2c_smbus_write_quick(struct i2c_client * client, u8 value); | |
689 | extern s32 i2c_smbus_read_byte(struct i2c_client * client); | |
690 | extern s32 i2c_smbus_write_byte(struct i2c_client * client, u8 value); | |
691 | extern s32 i2c_smbus_read_byte_data(struct i2c_client * client, u8 command); | |
692 | extern s32 i2c_smbus_write_byte_data(struct i2c_client * client, | |
693 | u8 command, u8 value); | |
694 | extern s32 i2c_smbus_read_word_data(struct i2c_client * client, u8 command); | |
695 | extern s32 i2c_smbus_write_word_data(struct i2c_client * client, | |
696 | u8 command, u16 value); | |
697 | extern s32 i2c_smbus_write_block_data(struct i2c_client * client, | |
698 | u8 command, u8 length, | |
699 | u8 *values); | |
7865e249 JD |
700 | extern s32 i2c_smbus_read_i2c_block_data(struct i2c_client * client, |
701 | u8 command, u8 *values); | |
1da177e4 LT |
702 | |
703 | These ones were removed in Linux 2.6.10 because they had no users, but could | |
704 | be added back later if needed: | |
705 | ||
1da177e4 LT |
706 | extern s32 i2c_smbus_read_block_data(struct i2c_client * client, |
707 | u8 command, u8 *values); | |
708 | extern s32 i2c_smbus_write_i2c_block_data(struct i2c_client * client, | |
709 | u8 command, u8 length, | |
710 | u8 *values); | |
711 | extern s32 i2c_smbus_process_call(struct i2c_client * client, | |
712 | u8 command, u16 value); | |
713 | extern s32 i2c_smbus_block_process_call(struct i2c_client *client, | |
714 | u8 command, u8 length, | |
715 | u8 *values) | |
716 | ||
717 | All these transactions return -1 on failure. The 'write' transactions | |
718 | return 0 on success; the 'read' transactions return the read value, except | |
719 | for read_block, which returns the number of values read. The block buffers | |
720 | need not be longer than 32 bytes. | |
721 | ||
722 | You can read the file `smbus-protocol' for more information about the | |
723 | actual SMBus protocol. | |
724 | ||
725 | ||
726 | General purpose routines | |
727 | ======================== | |
728 | ||
729 | Below all general purpose routines are listed, that were not mentioned | |
730 | before. | |
731 | ||
732 | /* This call returns a unique low identifier for each registered adapter, | |
733 | * or -1 if the adapter was not registered. | |
734 | */ | |
735 | extern int i2c_adapter_id(struct i2c_adapter *adap); | |
736 | ||
737 | ||
738 | The sensors sysctl/proc interface | |
739 | ================================= | |
740 | ||
741 | This section only applies if you write `sensors' drivers. | |
742 | ||
743 | Each sensors driver creates a directory in /proc/sys/dev/sensors for each | |
744 | registered client. The directory is called something like foo-i2c-4-65. | |
745 | The sensors module helps you to do this as easily as possible. | |
746 | ||
747 | The template | |
748 | ------------ | |
749 | ||
750 | You will need to define a ctl_table template. This template will automatically | |
751 | be copied to a newly allocated structure and filled in where necessary when | |
752 | you call sensors_register_entry. | |
753 | ||
754 | First, I will give an example definition. | |
755 | static ctl_table foo_dir_table_template[] = { | |
756 | { FOO_SYSCTL_FUNC1, "func1", NULL, 0, 0644, NULL, &i2c_proc_real, | |
757 | &i2c_sysctl_real,NULL,&foo_func }, | |
758 | { FOO_SYSCTL_FUNC2, "func2", NULL, 0, 0644, NULL, &i2c_proc_real, | |
759 | &i2c_sysctl_real,NULL,&foo_func }, | |
760 | { FOO_SYSCTL_DATA, "data", NULL, 0, 0644, NULL, &i2c_proc_real, | |
761 | &i2c_sysctl_real,NULL,&foo_data }, | |
762 | { 0 } | |
763 | }; | |
764 | ||
765 | In the above example, three entries are defined. They can either be | |
766 | accessed through the /proc interface, in the /proc/sys/dev/sensors/* | |
767 | directories, as files named func1, func2 and data, or alternatively | |
768 | through the sysctl interface, in the appropriate table, with identifiers | |
769 | FOO_SYSCTL_FUNC1, FOO_SYSCTL_FUNC2 and FOO_SYSCTL_DATA. | |
770 | ||
771 | The third, sixth and ninth parameters should always be NULL, and the | |
772 | fourth should always be 0. The fifth is the mode of the /proc file; | |
773 | 0644 is safe, as the file will be owned by root:root. | |
774 | ||
775 | The seventh and eighth parameters should be &i2c_proc_real and | |
776 | &i2c_sysctl_real if you want to export lists of reals (scaled | |
777 | integers). You can also use your own function for them, as usual. | |
778 | Finally, the last parameter is the call-back to gather the data | |
779 | (see below) if you use the *_proc_real functions. | |
780 | ||
781 | ||
782 | Gathering the data | |
783 | ------------------ | |
784 | ||
785 | The call back functions (foo_func and foo_data in the above example) | |
786 | can be called in several ways; the operation parameter determines | |
787 | what should be done: | |
788 | ||
789 | * If operation == SENSORS_PROC_REAL_INFO, you must return the | |
790 | magnitude (scaling) in nrels_mag; | |
791 | * If operation == SENSORS_PROC_REAL_READ, you must read information | |
792 | from the chip and return it in results. The number of integers | |
793 | to display should be put in nrels_mag; | |
794 | * If operation == SENSORS_PROC_REAL_WRITE, you must write the | |
795 | supplied information to the chip. nrels_mag will contain the number | |
796 | of integers, results the integers themselves. | |
797 | ||
798 | The *_proc_real functions will display the elements as reals for the | |
799 | /proc interface. If you set the magnitude to 2, and supply 345 for | |
800 | SENSORS_PROC_REAL_READ, it would display 3.45; and if the user would | |
801 | write 45.6 to the /proc file, it would be returned as 4560 for | |
802 | SENSORS_PROC_REAL_WRITE. A magnitude may even be negative! | |
803 | ||
804 | An example function: | |
805 | ||
806 | /* FOO_FROM_REG and FOO_TO_REG translate between scaled values and | |
807 | register values. Note the use of the read cache. */ | |
808 | void foo_in(struct i2c_client *client, int operation, int ctl_name, | |
809 | int *nrels_mag, long *results) | |
810 | { | |
811 | struct foo_data *data = client->data; | |
812 | int nr = ctl_name - FOO_SYSCTL_FUNC1; /* reduce to 0 upwards */ | |
813 | ||
814 | if (operation == SENSORS_PROC_REAL_INFO) | |
815 | *nrels_mag = 2; | |
816 | else if (operation == SENSORS_PROC_REAL_READ) { | |
817 | /* Update the readings cache (if necessary) */ | |
818 | foo_update_client(client); | |
819 | /* Get the readings from the cache */ | |
820 | results[0] = FOO_FROM_REG(data->foo_func_base[nr]); | |
821 | results[1] = FOO_FROM_REG(data->foo_func_more[nr]); | |
822 | results[2] = FOO_FROM_REG(data->foo_func_readonly[nr]); | |
823 | *nrels_mag = 2; | |
824 | } else if (operation == SENSORS_PROC_REAL_WRITE) { | |
825 | if (*nrels_mag >= 1) { | |
826 | /* Update the cache */ | |
827 | data->foo_base[nr] = FOO_TO_REG(results[0]); | |
828 | /* Update the chip */ | |
829 | foo_write_value(client,FOO_REG_FUNC_BASE(nr),data->foo_base[nr]); | |
830 | } | |
831 | if (*nrels_mag >= 2) { | |
832 | /* Update the cache */ | |
833 | data->foo_more[nr] = FOO_TO_REG(results[1]); | |
834 | /* Update the chip */ | |
835 | foo_write_value(client,FOO_REG_FUNC_MORE(nr),data->foo_more[nr]); | |
836 | } | |
837 | } | |
838 | } |