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