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1da177e4 LT |
1 | This is a small guide for those who want to write kernel drivers for I2C |
2 | or SMBus devices. | |
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 | |
24 | routines, a client structure specific information like the actual I2C | |
25 | address. | |
26 | ||
27 | static struct i2c_driver foo_driver = { | |
28 | .owner = THIS_MODULE, | |
29 | .name = "Foo version 2.3 driver", | |
1da177e4 LT |
30 | .attach_adapter = &foo_attach_adapter, |
31 | .detach_client = &foo_detach_client, | |
32 | .command = &foo_command /* may be NULL */ | |
33 | } | |
34 | ||
7865e249 JD |
35 | The name field must match the driver name, including the case. It must not |
36 | contain spaces, and may be up to 31 characters long. | |
1da177e4 | 37 | |
1da177e4 LT |
38 | All other fields are for call-back functions which will be explained |
39 | below. | |
40 | ||
1da177e4 LT |
41 | |
42 | Extra client data | |
43 | ================= | |
44 | ||
45 | The client structure has a special `data' field that can point to any | |
46 | structure at all. You can use this to keep client-specific data. You | |
47 | do not always need this, but especially for `sensors' drivers, it can | |
48 | be very useful. | |
49 | ||
50 | An example structure is below. | |
51 | ||
52 | struct foo_data { | |
2445eb62 | 53 | struct i2c_client client; |
1da177e4 LT |
54 | struct semaphore lock; /* For ISA access in `sensors' drivers. */ |
55 | int sysctl_id; /* To keep the /proc directory entry for | |
56 | `sensors' drivers. */ | |
57 | enum chips type; /* To keep the chips type for `sensors' drivers. */ | |
58 | ||
59 | /* Because the i2c bus is slow, it is often useful to cache the read | |
60 | information of a chip for some time (for example, 1 or 2 seconds). | |
61 | It depends of course on the device whether this is really worthwhile | |
62 | or even sensible. */ | |
63 | struct semaphore update_lock; /* When we are reading lots of information, | |
64 | another process should not update the | |
65 | below information */ | |
66 | char valid; /* != 0 if the following fields are valid. */ | |
67 | unsigned long last_updated; /* In jiffies */ | |
68 | /* Add the read information here too */ | |
69 | }; | |
70 | ||
71 | ||
72 | Accessing the client | |
73 | ==================== | |
74 | ||
75 | Let's say we have a valid client structure. At some time, we will need | |
76 | to gather information from the client, or write new information to the | |
77 | client. How we will export this information to user-space is less | |
78 | important at this moment (perhaps we do not need to do this at all for | |
79 | some obscure clients). But we need generic reading and writing routines. | |
80 | ||
81 | I have found it useful to define foo_read and foo_write function for this. | |
82 | For some cases, it will be easier to call the i2c functions directly, | |
83 | but many chips have some kind of register-value idea that can easily | |
84 | be encapsulated. Also, some chips have both ISA and I2C interfaces, and | |
85 | it useful to abstract from this (only for `sensors' drivers). | |
86 | ||
87 | The below functions are simple examples, and should not be copied | |
88 | literally. | |
89 | ||
90 | int foo_read_value(struct i2c_client *client, u8 reg) | |
91 | { | |
92 | if (reg < 0x10) /* byte-sized register */ | |
93 | return i2c_smbus_read_byte_data(client,reg); | |
94 | else /* word-sized register */ | |
95 | return i2c_smbus_read_word_data(client,reg); | |
96 | } | |
97 | ||
98 | int foo_write_value(struct i2c_client *client, u8 reg, u16 value) | |
99 | { | |
100 | if (reg == 0x10) /* Impossible to write - driver error! */ { | |
101 | return -1; | |
102 | else if (reg < 0x10) /* byte-sized register */ | |
103 | return i2c_smbus_write_byte_data(client,reg,value); | |
104 | else /* word-sized register */ | |
105 | return i2c_smbus_write_word_data(client,reg,value); | |
106 | } | |
107 | ||
108 | For sensors code, you may have to cope with ISA registers too. Something | |
109 | like the below often works. Note the locking! | |
110 | ||
111 | int foo_read_value(struct i2c_client *client, u8 reg) | |
112 | { | |
113 | int res; | |
114 | if (i2c_is_isa_client(client)) { | |
115 | down(&(((struct foo_data *) (client->data)) -> lock)); | |
116 | outb_p(reg,client->addr + FOO_ADDR_REG_OFFSET); | |
117 | res = inb_p(client->addr + FOO_DATA_REG_OFFSET); | |
118 | up(&(((struct foo_data *) (client->data)) -> lock)); | |
119 | return res; | |
120 | } else | |
121 | return i2c_smbus_read_byte_data(client,reg); | |
122 | } | |
123 | ||
124 | Writing is done the same way. | |
125 | ||
126 | ||
127 | Probing and attaching | |
128 | ===================== | |
129 | ||
130 | Most i2c devices can be present on several i2c addresses; for some this | |
131 | is determined in hardware (by soldering some chip pins to Vcc or Ground), | |
132 | for others this can be changed in software (by writing to specific client | |
133 | registers). Some devices are usually on a specific address, but not always; | |
134 | and some are even more tricky. So you will probably need to scan several | |
135 | i2c addresses for your clients, and do some sort of detection to see | |
136 | whether it is actually a device supported by your driver. | |
137 | ||
138 | To give the user a maximum of possibilities, some default module parameters | |
139 | are defined to help determine what addresses are scanned. Several macros | |
140 | are defined in i2c.h to help you support them, as well as a generic | |
141 | detection algorithm. | |
142 | ||
143 | You do not have to use this parameter interface; but don't try to use | |
2ed2dc3c | 144 | function i2c_probe() if you don't. |
1da177e4 LT |
145 | |
146 | NOTE: If you want to write a `sensors' driver, the interface is slightly | |
147 | different! See below. | |
148 | ||
149 | ||
150 | ||
f4b50261 JD |
151 | Probing classes |
152 | --------------- | |
1da177e4 LT |
153 | |
154 | All parameters are given as lists of unsigned 16-bit integers. Lists are | |
155 | terminated by I2C_CLIENT_END. | |
156 | The following lists are used internally: | |
157 | ||
158 | normal_i2c: filled in by the module writer. | |
159 | A list of I2C addresses which should normally be examined. | |
1da177e4 LT |
160 | probe: insmod parameter. |
161 | A list of pairs. The first value is a bus number (-1 for any I2C bus), | |
162 | the second is the address. These addresses are also probed, as if they | |
163 | were in the 'normal' list. | |
1da177e4 LT |
164 | ignore: insmod parameter. |
165 | A list of pairs. The first value is a bus number (-1 for any I2C bus), | |
166 | the second is the I2C address. These addresses are never probed. | |
f4b50261 | 167 | This parameter overrules the 'normal_i2c' list only. |
1da177e4 LT |
168 | force: insmod parameter. |
169 | A list of pairs. The first value is a bus number (-1 for any I2C bus), | |
170 | the second is the I2C address. A device is blindly assumed to be on | |
171 | the given address, no probing is done. | |
172 | ||
f4b50261 JD |
173 | Additionally, kind-specific force lists may optionally be defined if |
174 | the driver supports several chip kinds. They are grouped in a | |
175 | NULL-terminated list of pointers named forces, those first element if the | |
176 | generic force list mentioned above. Each additional list correspond to an | |
177 | insmod parameter of the form force_<kind>. | |
178 | ||
b3d5496e JD |
179 | Fortunately, as a module writer, you just have to define the `normal_i2c' |
180 | parameter. The complete declaration could look like this: | |
1da177e4 | 181 | |
b3d5496e JD |
182 | /* Scan 0x37, and 0x48 to 0x4f */ |
183 | static unsigned short normal_i2c[] = { 0x37, 0x48, 0x49, 0x4a, 0x4b, 0x4c, | |
184 | 0x4d, 0x4e, 0x4f, I2C_CLIENT_END }; | |
1da177e4 LT |
185 | |
186 | /* Magic definition of all other variables and things */ | |
187 | I2C_CLIENT_INSMOD; | |
f4b50261 JD |
188 | /* Or, if your driver supports, say, 2 kind of devices: */ |
189 | I2C_CLIENT_INSMOD_2(foo, bar); | |
190 | ||
191 | If you use the multi-kind form, an enum will be defined for you: | |
192 | enum chips { any_chip, foo, bar, ... } | |
193 | You can then (and certainly should) use it in the driver code. | |
1da177e4 | 194 | |
b3d5496e JD |
195 | Note that you *have* to call the defined variable `normal_i2c', |
196 | without any prefix! | |
1da177e4 LT |
197 | |
198 | ||
1da177e4 LT |
199 | Attaching to an adapter |
200 | ----------------------- | |
201 | ||
202 | Whenever a new adapter is inserted, or for all adapters if the driver is | |
203 | being registered, the callback attach_adapter() is called. Now is the | |
204 | time to determine what devices are present on the adapter, and to register | |
205 | a client for each of them. | |
206 | ||
207 | The attach_adapter callback is really easy: we just call the generic | |
208 | detection function. This function will scan the bus for us, using the | |
209 | information as defined in the lists explained above. If a device is | |
210 | detected at a specific address, another callback is called. | |
211 | ||
212 | int foo_attach_adapter(struct i2c_adapter *adapter) | |
213 | { | |
214 | return i2c_probe(adapter,&addr_data,&foo_detect_client); | |
215 | } | |
216 | ||
1da177e4 LT |
217 | Remember, structure `addr_data' is defined by the macros explained above, |
218 | so you do not have to define it yourself. | |
219 | ||
2ed2dc3c | 220 | The i2c_probe function will call the foo_detect_client |
1da177e4 LT |
221 | function only for those i2c addresses that actually have a device on |
222 | them (unless a `force' parameter was used). In addition, addresses that | |
223 | are already in use (by some other registered client) are skipped. | |
224 | ||
225 | ||
226 | The detect client function | |
227 | -------------------------- | |
228 | ||
2ed2dc3c JD |
229 | The detect client function is called by i2c_probe. The `kind' parameter |
230 | contains -1 for a probed detection, 0 for a forced detection, or a positive | |
231 | number for a forced detection with a chip type forced. | |
1da177e4 LT |
232 | |
233 | Below, some things are only needed if this is a `sensors' driver. Those | |
234 | parts are between /* SENSORS ONLY START */ and /* SENSORS ONLY END */ | |
235 | markers. | |
236 | ||
a89ba0bc JD |
237 | Returning an error different from -ENODEV in a detect function will cause |
238 | the detection to stop: other addresses and adapters won't be scanned. | |
239 | This should only be done on fatal or internal errors, such as a memory | |
240 | shortage or i2c_attach_client failing. | |
1da177e4 LT |
241 | |
242 | For now, you can ignore the `flags' parameter. It is there for future use. | |
243 | ||
244 | int foo_detect_client(struct i2c_adapter *adapter, int address, | |
245 | unsigned short flags, int kind) | |
246 | { | |
247 | int err = 0; | |
248 | int i; | |
249 | struct i2c_client *new_client; | |
250 | struct foo_data *data; | |
251 | const char *client_name = ""; /* For non-`sensors' drivers, put the real | |
252 | name here! */ | |
253 | ||
254 | /* Let's see whether this adapter can support what we need. | |
255 | Please substitute the things you need here! | |
256 | For `sensors' drivers, add `! is_isa &&' to the if statement */ | |
257 | if (!i2c_check_functionality(adapter,I2C_FUNC_SMBUS_WORD_DATA | | |
258 | I2C_FUNC_SMBUS_WRITE_BYTE)) | |
259 | goto ERROR0; | |
260 | ||
261 | /* SENSORS ONLY START */ | |
262 | const char *type_name = ""; | |
263 | int is_isa = i2c_is_isa_adapter(adapter); | |
264 | ||
02ff982c JD |
265 | /* Do this only if the chip can additionally be found on the ISA bus |
266 | (hybrid chip). */ | |
1da177e4 | 267 | |
02ff982c | 268 | if (is_isa) { |
1da177e4 LT |
269 | |
270 | /* Discard immediately if this ISA range is already used */ | |
d61780c0 | 271 | /* FIXME: never use check_region(), only request_region() */ |
1da177e4 LT |
272 | if (check_region(address,FOO_EXTENT)) |
273 | goto ERROR0; | |
274 | ||
275 | /* Probe whether there is anything on this address. | |
276 | Some example code is below, but you will have to adapt this | |
277 | for your own driver */ | |
278 | ||
279 | if (kind < 0) /* Only if no force parameter was used */ { | |
280 | /* We may need long timeouts at least for some chips. */ | |
281 | #define REALLY_SLOW_IO | |
282 | i = inb_p(address + 1); | |
283 | if (inb_p(address + 2) != i) | |
284 | goto ERROR0; | |
285 | if (inb_p(address + 3) != i) | |
286 | goto ERROR0; | |
287 | if (inb_p(address + 7) != i) | |
288 | goto ERROR0; | |
289 | #undef REALLY_SLOW_IO | |
290 | ||
291 | /* Let's just hope nothing breaks here */ | |
292 | i = inb_p(address + 5) & 0x7f; | |
293 | outb_p(~i & 0x7f,address+5); | |
294 | if ((inb_p(address + 5) & 0x7f) != (~i & 0x7f)) { | |
295 | outb_p(i,address+5); | |
296 | return 0; | |
297 | } | |
298 | } | |
299 | } | |
300 | ||
301 | /* SENSORS ONLY END */ | |
302 | ||
303 | /* OK. For now, we presume we have a valid client. We now create the | |
304 | client structure, even though we cannot fill it completely yet. | |
305 | But it allows us to access several i2c functions safely */ | |
306 | ||
2445eb62 | 307 | if (!(data = kzalloc(sizeof(struct foo_data), GFP_KERNEL))) { |
1da177e4 LT |
308 | err = -ENOMEM; |
309 | goto ERROR0; | |
310 | } | |
311 | ||
2445eb62 JD |
312 | new_client = &data->client; |
313 | i2c_set_clientdata(new_client, data); | |
1da177e4 LT |
314 | |
315 | new_client->addr = address; | |
1da177e4 LT |
316 | new_client->adapter = adapter; |
317 | new_client->driver = &foo_driver; | |
318 | new_client->flags = 0; | |
319 | ||
320 | /* Now, we do the remaining detection. If no `force' parameter is used. */ | |
321 | ||
322 | /* First, the generic detection (if any), that is skipped if any force | |
323 | parameter was used. */ | |
324 | if (kind < 0) { | |
325 | /* The below is of course bogus */ | |
326 | if (foo_read(new_client,FOO_REG_GENERIC) != FOO_GENERIC_VALUE) | |
327 | goto ERROR1; | |
328 | } | |
329 | ||
330 | /* SENSORS ONLY START */ | |
331 | ||
332 | /* Next, specific detection. This is especially important for `sensors' | |
333 | devices. */ | |
334 | ||
335 | /* Determine the chip type. Not needed if a `force_CHIPTYPE' parameter | |
336 | was used. */ | |
337 | if (kind <= 0) { | |
338 | i = foo_read(new_client,FOO_REG_CHIPTYPE); | |
339 | if (i == FOO_TYPE_1) | |
340 | kind = chip1; /* As defined in the enum */ | |
341 | else if (i == FOO_TYPE_2) | |
342 | kind = chip2; | |
343 | else { | |
344 | printk("foo: Ignoring 'force' parameter for unknown chip at " | |
345 | "adapter %d, address 0x%02x\n",i2c_adapter_id(adapter),address); | |
346 | goto ERROR1; | |
347 | } | |
348 | } | |
349 | ||
350 | /* Now set the type and chip names */ | |
351 | if (kind == chip1) { | |
352 | type_name = "chip1"; /* For /proc entry */ | |
353 | client_name = "CHIP 1"; | |
354 | } else if (kind == chip2) { | |
355 | type_name = "chip2"; /* For /proc entry */ | |
356 | client_name = "CHIP 2"; | |
357 | } | |
358 | ||
359 | /* Reserve the ISA region */ | |
360 | if (is_isa) | |
361 | request_region(address,FOO_EXTENT,type_name); | |
362 | ||
363 | /* SENSORS ONLY END */ | |
364 | ||
365 | /* Fill in the remaining client fields. */ | |
366 | strcpy(new_client->name,client_name); | |
367 | ||
368 | /* SENSORS ONLY BEGIN */ | |
369 | data->type = kind; | |
370 | /* SENSORS ONLY END */ | |
371 | ||
372 | data->valid = 0; /* Only if you use this field */ | |
373 | init_MUTEX(&data->update_lock); /* Only if you use this field */ | |
374 | ||
375 | /* Any other initializations in data must be done here too. */ | |
376 | ||
377 | /* Tell the i2c layer a new client has arrived */ | |
378 | if ((err = i2c_attach_client(new_client))) | |
379 | goto ERROR3; | |
380 | ||
381 | /* SENSORS ONLY BEGIN */ | |
382 | /* Register a new directory entry with module sensors. See below for | |
383 | the `template' structure. */ | |
384 | if ((i = i2c_register_entry(new_client, type_name, | |
385 | foo_dir_table_template,THIS_MODULE)) < 0) { | |
386 | err = i; | |
387 | goto ERROR4; | |
388 | } | |
389 | data->sysctl_id = i; | |
390 | ||
391 | /* SENSORS ONLY END */ | |
392 | ||
393 | /* This function can write default values to the client registers, if | |
394 | needed. */ | |
395 | foo_init_client(new_client); | |
396 | return 0; | |
397 | ||
398 | /* OK, this is not exactly good programming practice, usually. But it is | |
399 | very code-efficient in this case. */ | |
400 | ||
401 | ERROR4: | |
402 | i2c_detach_client(new_client); | |
403 | ERROR3: | |
404 | ERROR2: | |
405 | /* SENSORS ONLY START */ | |
406 | if (is_isa) | |
407 | release_region(address,FOO_EXTENT); | |
408 | /* SENSORS ONLY END */ | |
409 | ERROR1: | |
a852daa0 | 410 | kfree(data); |
1da177e4 LT |
411 | ERROR0: |
412 | return err; | |
413 | } | |
414 | ||
415 | ||
416 | Removing the client | |
417 | =================== | |
418 | ||
419 | The detach_client call back function is called when a client should be | |
420 | removed. It may actually fail, but only when panicking. This code is | |
421 | much simpler than the attachment code, fortunately! | |
422 | ||
423 | int foo_detach_client(struct i2c_client *client) | |
424 | { | |
425 | int err,i; | |
426 | ||
427 | /* SENSORS ONLY START */ | |
428 | /* Deregister with the `i2c-proc' module. */ | |
429 | i2c_deregister_entry(((struct lm78_data *)(client->data))->sysctl_id); | |
430 | /* SENSORS ONLY END */ | |
431 | ||
432 | /* Try to detach the client from i2c space */ | |
7bef5594 | 433 | if ((err = i2c_detach_client(client))) |
1da177e4 | 434 | return err; |
1da177e4 | 435 | |
02ff982c | 436 | /* HYBRID SENSORS CHIP ONLY START */ |
1da177e4 LT |
437 | if i2c_is_isa_client(client) |
438 | release_region(client->addr,LM78_EXTENT); | |
02ff982c | 439 | /* HYBRID SENSORS CHIP ONLY END */ |
1da177e4 | 440 | |
a852daa0 | 441 | kfree(i2c_get_clientdata(client)); |
1da177e4 LT |
442 | return 0; |
443 | } | |
444 | ||
445 | ||
446 | Initializing the module or kernel | |
447 | ================================= | |
448 | ||
449 | When the kernel is booted, or when your foo driver module is inserted, | |
450 | you have to do some initializing. Fortunately, just attaching (registering) | |
451 | the driver module is usually enough. | |
452 | ||
453 | /* Keep track of how far we got in the initialization process. If several | |
454 | things have to initialized, and we fail halfway, only those things | |
455 | have to be cleaned up! */ | |
456 | static int __initdata foo_initialized = 0; | |
457 | ||
458 | static int __init foo_init(void) | |
459 | { | |
460 | int res; | |
461 | printk("foo version %s (%s)\n",FOO_VERSION,FOO_DATE); | |
462 | ||
463 | if ((res = i2c_add_driver(&foo_driver))) { | |
464 | printk("foo: Driver registration failed, module not inserted.\n"); | |
465 | foo_cleanup(); | |
466 | return res; | |
467 | } | |
468 | foo_initialized ++; | |
469 | return 0; | |
470 | } | |
471 | ||
472 | void foo_cleanup(void) | |
473 | { | |
474 | if (foo_initialized == 1) { | |
475 | if ((res = i2c_del_driver(&foo_driver))) { | |
476 | printk("foo: Driver registration failed, module not removed.\n"); | |
477 | return; | |
478 | } | |
479 | foo_initialized --; | |
480 | } | |
481 | } | |
482 | ||
483 | /* Substitute your own name and email address */ | |
484 | MODULE_AUTHOR("Frodo Looijaard <frodol@dds.nl>" | |
485 | MODULE_DESCRIPTION("Driver for Barf Inc. Foo I2C devices"); | |
486 | ||
487 | module_init(foo_init); | |
488 | module_exit(foo_cleanup); | |
489 | ||
490 | Note that some functions are marked by `__init', and some data structures | |
491 | by `__init_data'. Hose functions and structures can be removed after | |
492 | kernel booting (or module loading) is completed. | |
493 | ||
494 | Command function | |
495 | ================ | |
496 | ||
497 | A generic ioctl-like function call back is supported. You will seldom | |
498 | need this. You may even set it to NULL. | |
499 | ||
500 | /* No commands defined */ | |
501 | int foo_command(struct i2c_client *client, unsigned int cmd, void *arg) | |
502 | { | |
503 | return 0; | |
504 | } | |
505 | ||
506 | ||
507 | Sending and receiving | |
508 | ===================== | |
509 | ||
510 | If you want to communicate with your device, there are several functions | |
511 | to do this. You can find all of them in i2c.h. | |
512 | ||
513 | If you can choose between plain i2c communication and SMBus level | |
514 | communication, please use the last. All adapters understand SMBus level | |
515 | commands, but only some of them understand plain i2c! | |
516 | ||
517 | ||
518 | Plain i2c communication | |
519 | ----------------------- | |
520 | ||
521 | extern int i2c_master_send(struct i2c_client *,const char* ,int); | |
522 | extern int i2c_master_recv(struct i2c_client *,char* ,int); | |
523 | ||
524 | These routines read and write some bytes from/to a client. The client | |
525 | contains the i2c address, so you do not have to include it. The second | |
526 | parameter contains the bytes the read/write, the third the length of the | |
527 | buffer. Returned is the actual number of bytes read/written. | |
528 | ||
529 | extern int i2c_transfer(struct i2c_adapter *adap, struct i2c_msg *msg, | |
530 | int num); | |
531 | ||
532 | This sends a series of messages. Each message can be a read or write, | |
533 | and they can be mixed in any way. The transactions are combined: no | |
534 | stop bit is sent between transaction. The i2c_msg structure contains | |
535 | for each message the client address, the number of bytes of the message | |
536 | and the message data itself. | |
537 | ||
538 | You can read the file `i2c-protocol' for more information about the | |
539 | actual i2c protocol. | |
540 | ||
541 | ||
542 | SMBus communication | |
543 | ------------------- | |
544 | ||
545 | extern s32 i2c_smbus_xfer (struct i2c_adapter * adapter, u16 addr, | |
546 | unsigned short flags, | |
547 | char read_write, u8 command, int size, | |
548 | union i2c_smbus_data * data); | |
549 | ||
550 | This is the generic SMBus function. All functions below are implemented | |
551 | in terms of it. Never use this function directly! | |
552 | ||
553 | ||
554 | extern s32 i2c_smbus_write_quick(struct i2c_client * client, u8 value); | |
555 | extern s32 i2c_smbus_read_byte(struct i2c_client * client); | |
556 | extern s32 i2c_smbus_write_byte(struct i2c_client * client, u8 value); | |
557 | extern s32 i2c_smbus_read_byte_data(struct i2c_client * client, u8 command); | |
558 | extern s32 i2c_smbus_write_byte_data(struct i2c_client * client, | |
559 | u8 command, u8 value); | |
560 | extern s32 i2c_smbus_read_word_data(struct i2c_client * client, u8 command); | |
561 | extern s32 i2c_smbus_write_word_data(struct i2c_client * client, | |
562 | u8 command, u16 value); | |
563 | extern s32 i2c_smbus_write_block_data(struct i2c_client * client, | |
564 | u8 command, u8 length, | |
565 | u8 *values); | |
7865e249 JD |
566 | extern s32 i2c_smbus_read_i2c_block_data(struct i2c_client * client, |
567 | u8 command, u8 *values); | |
1da177e4 LT |
568 | |
569 | These ones were removed in Linux 2.6.10 because they had no users, but could | |
570 | be added back later if needed: | |
571 | ||
1da177e4 LT |
572 | extern s32 i2c_smbus_read_block_data(struct i2c_client * client, |
573 | u8 command, u8 *values); | |
574 | extern s32 i2c_smbus_write_i2c_block_data(struct i2c_client * client, | |
575 | u8 command, u8 length, | |
576 | u8 *values); | |
577 | extern s32 i2c_smbus_process_call(struct i2c_client * client, | |
578 | u8 command, u16 value); | |
579 | extern s32 i2c_smbus_block_process_call(struct i2c_client *client, | |
580 | u8 command, u8 length, | |
581 | u8 *values) | |
582 | ||
583 | All these transactions return -1 on failure. The 'write' transactions | |
584 | return 0 on success; the 'read' transactions return the read value, except | |
585 | for read_block, which returns the number of values read. The block buffers | |
586 | need not be longer than 32 bytes. | |
587 | ||
588 | You can read the file `smbus-protocol' for more information about the | |
589 | actual SMBus protocol. | |
590 | ||
591 | ||
592 | General purpose routines | |
593 | ======================== | |
594 | ||
595 | Below all general purpose routines are listed, that were not mentioned | |
596 | before. | |
597 | ||
598 | /* This call returns a unique low identifier for each registered adapter, | |
599 | * or -1 if the adapter was not registered. | |
600 | */ | |
601 | extern int i2c_adapter_id(struct i2c_adapter *adap); | |
602 | ||
603 | ||
604 | The sensors sysctl/proc interface | |
605 | ================================= | |
606 | ||
607 | This section only applies if you write `sensors' drivers. | |
608 | ||
609 | Each sensors driver creates a directory in /proc/sys/dev/sensors for each | |
610 | registered client. The directory is called something like foo-i2c-4-65. | |
611 | The sensors module helps you to do this as easily as possible. | |
612 | ||
613 | The template | |
614 | ------------ | |
615 | ||
616 | You will need to define a ctl_table template. This template will automatically | |
617 | be copied to a newly allocated structure and filled in where necessary when | |
618 | you call sensors_register_entry. | |
619 | ||
620 | First, I will give an example definition. | |
621 | static ctl_table foo_dir_table_template[] = { | |
622 | { FOO_SYSCTL_FUNC1, "func1", NULL, 0, 0644, NULL, &i2c_proc_real, | |
623 | &i2c_sysctl_real,NULL,&foo_func }, | |
624 | { FOO_SYSCTL_FUNC2, "func2", NULL, 0, 0644, NULL, &i2c_proc_real, | |
625 | &i2c_sysctl_real,NULL,&foo_func }, | |
626 | { FOO_SYSCTL_DATA, "data", NULL, 0, 0644, NULL, &i2c_proc_real, | |
627 | &i2c_sysctl_real,NULL,&foo_data }, | |
628 | { 0 } | |
629 | }; | |
630 | ||
631 | In the above example, three entries are defined. They can either be | |
632 | accessed through the /proc interface, in the /proc/sys/dev/sensors/* | |
633 | directories, as files named func1, func2 and data, or alternatively | |
634 | through the sysctl interface, in the appropriate table, with identifiers | |
635 | FOO_SYSCTL_FUNC1, FOO_SYSCTL_FUNC2 and FOO_SYSCTL_DATA. | |
636 | ||
637 | The third, sixth and ninth parameters should always be NULL, and the | |
638 | fourth should always be 0. The fifth is the mode of the /proc file; | |
639 | 0644 is safe, as the file will be owned by root:root. | |
640 | ||
641 | The seventh and eighth parameters should be &i2c_proc_real and | |
642 | &i2c_sysctl_real if you want to export lists of reals (scaled | |
643 | integers). You can also use your own function for them, as usual. | |
644 | Finally, the last parameter is the call-back to gather the data | |
645 | (see below) if you use the *_proc_real functions. | |
646 | ||
647 | ||
648 | Gathering the data | |
649 | ------------------ | |
650 | ||
651 | The call back functions (foo_func and foo_data in the above example) | |
652 | can be called in several ways; the operation parameter determines | |
653 | what should be done: | |
654 | ||
655 | * If operation == SENSORS_PROC_REAL_INFO, you must return the | |
656 | magnitude (scaling) in nrels_mag; | |
657 | * If operation == SENSORS_PROC_REAL_READ, you must read information | |
658 | from the chip and return it in results. The number of integers | |
659 | to display should be put in nrels_mag; | |
660 | * If operation == SENSORS_PROC_REAL_WRITE, you must write the | |
661 | supplied information to the chip. nrels_mag will contain the number | |
662 | of integers, results the integers themselves. | |
663 | ||
664 | The *_proc_real functions will display the elements as reals for the | |
665 | /proc interface. If you set the magnitude to 2, and supply 345 for | |
666 | SENSORS_PROC_REAL_READ, it would display 3.45; and if the user would | |
667 | write 45.6 to the /proc file, it would be returned as 4560 for | |
668 | SENSORS_PROC_REAL_WRITE. A magnitude may even be negative! | |
669 | ||
670 | An example function: | |
671 | ||
672 | /* FOO_FROM_REG and FOO_TO_REG translate between scaled values and | |
673 | register values. Note the use of the read cache. */ | |
674 | void foo_in(struct i2c_client *client, int operation, int ctl_name, | |
675 | int *nrels_mag, long *results) | |
676 | { | |
677 | struct foo_data *data = client->data; | |
678 | int nr = ctl_name - FOO_SYSCTL_FUNC1; /* reduce to 0 upwards */ | |
679 | ||
680 | if (operation == SENSORS_PROC_REAL_INFO) | |
681 | *nrels_mag = 2; | |
682 | else if (operation == SENSORS_PROC_REAL_READ) { | |
683 | /* Update the readings cache (if necessary) */ | |
684 | foo_update_client(client); | |
685 | /* Get the readings from the cache */ | |
686 | results[0] = FOO_FROM_REG(data->foo_func_base[nr]); | |
687 | results[1] = FOO_FROM_REG(data->foo_func_more[nr]); | |
688 | results[2] = FOO_FROM_REG(data->foo_func_readonly[nr]); | |
689 | *nrels_mag = 2; | |
690 | } else if (operation == SENSORS_PROC_REAL_WRITE) { | |
691 | if (*nrels_mag >= 1) { | |
692 | /* Update the cache */ | |
693 | data->foo_base[nr] = FOO_TO_REG(results[0]); | |
694 | /* Update the chip */ | |
695 | foo_write_value(client,FOO_REG_FUNC_BASE(nr),data->foo_base[nr]); | |
696 | } | |
697 | if (*nrels_mag >= 2) { | |
698 | /* Update the cache */ | |
699 | data->foo_more[nr] = FOO_TO_REG(results[1]); | |
700 | /* Update the chip */ | |
701 | foo_write_value(client,FOO_REG_FUNC_MORE(nr),data->foo_more[nr]); | |
702 | } | |
703 | } | |
704 | } |