aboutsummaryrefslogtreecommitdiffstats
path: root/drivers/i2c/chips/max6875.c
blob: 0230375f72e551bb227fda676eecadff0e5def79 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
/*
    max6875.c - driver for MAX6874/MAX6875

    Copyright (C) 2005 Ben Gardner <bgardner@wabtec.com>

    Based on i2c/chips/eeprom.c

    The MAX6875 has two EEPROM sections: config and user.
    At reset, the config EEPROM is read into the registers.

    This driver make 3 binary files available in sysfs:
      reg_config    - direct access to the registers
      eeprom_config - acesses configuration eeprom space
      eeprom_user   - free for application use

    In our application, we put device serial & model numbers in user eeprom.

    Notes:
      1) The datasheet says that register 0x44 / EEPROM 0x8044 should NOT
         be overwritten, so the driver explicitly prevents that.
      2) It's a good idea to keep the config (0x45) locked in config EEPROM.
         You can temporarily enable config writes by changing register 0x45.

    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; version 2 of the License.
*/

#include <linux/config.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/sched.h>
#include <linux/delay.h>
#include <linux/i2c.h>
#include <linux/i2c-sensor.h>

/* Addresses to scan */
/* No address scanned by default, as this could corrupt standard EEPROMS. */
static unsigned short normal_i2c[] = {I2C_CLIENT_END};
static unsigned int normal_isa[] = {I2C_CLIENT_ISA_END};

/* Insmod parameters */
SENSORS_INSMOD_1(max6875);

/* this param will prevent 'accidental' writes to the eeprom */
static int allow_write = 0;
module_param(allow_write, int, 0);
MODULE_PARM_DESC(allow_write,
		 "Enable write access:\n"
		 "*0: Read only\n"
		 " 1: Read/Write access");

/* The MAX6875 can only read/write 16 bytes at a time */
#define SLICE_SIZE			16
#define SLICE_BITS			4

/* CONFIG EEPROM is at addresses 0x8000 - 0x8045, registers are at 0 - 0x45 */
#define CONFIG_EEPROM_BASE		0x8000
#define CONFIG_EEPROM_SIZE		0x0046
#define CONFIG_EEPROM_SLICES		5

/* USER EEPROM is at addresses 0x8100 - 0x82FF */
#define USER_EEPROM_BASE		0x8100
#define USER_EEPROM_SIZE		0x0200
#define USER_EEPROM_SLICES		32

/* MAX6875 commands */
#define MAX6875_CMD_BLOCK_WRITE		0x83
#define MAX6875_CMD_BLOCK_READ		0x84
#define MAX6875_CMD_REBOOT		0x88

enum max6875_area_type {
	max6875_register_config=0,
	max6875_eeprom_config,
	max6875_eeprom_user,
	max6857_max
};

struct eeprom_block {
	enum max6875_area_type	type;
	u8			slices;
	u32			size;
	u32			valid;
	u32			base;
	unsigned long		*updated;
	u8			*data;
};

/* Each client has this additional data */
struct max6875_data {
	struct i2c_client	client;
	struct semaphore	update_lock;
	struct eeprom_block	blocks[max6857_max];
	/* the above structs point into the arrays below */
	u8 data[USER_EEPROM_SIZE + (CONFIG_EEPROM_SIZE*2)];
	unsigned long last_updated[USER_EEPROM_SLICES + (CONFIG_EEPROM_SLICES*2)];
};

static int max6875_attach_adapter(struct i2c_adapter *adapter);
static int max6875_detect(struct i2c_adapter *adapter, int address, int kind);
static int max6875_detach_client(struct i2c_client *client);

/* This is the driver that will be inserted */
static struct i2c_driver max6875_driver = {
	.owner		= THIS_MODULE,
	.name		= "max6875",
	.flags		= I2C_DF_NOTIFY,
	.attach_adapter	= max6875_attach_adapter,
	.detach_client	= max6875_detach_client,
};

static int max6875_update_slice(struct i2c_client *client,
				struct eeprom_block *blk,
				int slice)
{
	struct max6875_data *data = i2c_get_clientdata(client);
	int i, j, addr, count;
	u8 rdbuf[SLICE_SIZE];
	int retval = 0;

	if (slice >= blk->slices)
		return -1;

	down(&data->update_lock);

	if (!(blk->valid & (1 << slice)) ||
	    (jiffies - blk->updated[slice] > 300 * HZ) ||
	    (jiffies < blk->updated[slice])) {
		dev_dbg(&client->dev, "Starting eeprom update, slice %u, base %u\n",
			slice, blk->base);

		addr = blk->base + (slice << SLICE_BITS);
		count = blk->size - (slice << SLICE_BITS);
		if (count > SLICE_SIZE) {
			count = SLICE_SIZE;
		}

		/* Preset the read address */
		if (addr < 0x100) {
			/* select the register */
			if (i2c_smbus_write_byte(client, addr & 0xFF)) {
				dev_dbg(&client->dev, "max6875 register select has failed!\n");
				retval = -1;
				goto exit;
			}
		} else {
			/* select the eeprom */
			if (i2c_smbus_write_byte_data(client, addr >> 8, addr & 0xFF)) {
				dev_dbg(&client->dev, "max6875 address set has failed!\n");
				retval = -1;
				goto exit;
			}
		}

		if (i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_READ_I2C_BLOCK)) {
			if (i2c_smbus_read_i2c_block_data(client, MAX6875_CMD_BLOCK_READ,
							  rdbuf) != SLICE_SIZE)
			{
				retval = -1;
				goto exit;
			}

			memcpy(&blk->data[slice << SLICE_BITS], rdbuf, count);
		} else {
			for (i = 0; i < count; i++) {
				j = i2c_smbus_read_byte(client);
				if (j < 0)
				{
					retval = -1;
					goto exit;
				}
				blk->data[(slice << SLICE_BITS) + i] = (u8) j;
			}
		}
		blk->updated[slice] = jiffies;
		blk->valid |= (1 << slice);
	}
	exit:
	up(&data->update_lock);
	return retval;
}

static ssize_t max6875_read(struct kobject *kobj, char *buf, loff_t off, size_t count,
			    enum max6875_area_type area_type)
{
	struct i2c_client *client = to_i2c_client(container_of(kobj, struct device, kobj));
	struct max6875_data *data = i2c_get_clientdata(client);
	struct eeprom_block *blk;
	int slice;

	blk = &data->blocks[area_type];

	if (off > blk->size)
		return 0;
	if (off + count > blk->size)
		count = blk->size - off;

	/* Only refresh slices which contain requested bytes */
	for (slice = (off >> SLICE_BITS); slice <= ((off + count - 1) >> SLICE_BITS); slice++)
		max6875_update_slice(client, blk, slice);

	memcpy(buf, &blk->data[off], count);

	return count;
}

static ssize_t max6875_user_read(struct kobject *kobj, char *buf, loff_t off, size_t count)
{
	return max6875_read(kobj, buf, off, count, max6875_eeprom_user);
}

static ssize_t max6875_config_read(struct kobject *kobj, char *buf, loff_t off, size_t count)
{
	return max6875_read(kobj, buf, off, count, max6875_eeprom_config);
}

static ssize_t max6875_cfgreg_read(struct kobject *kobj, char *buf, loff_t off, size_t count)
{
	return max6875_read(kobj, buf, off, count, max6875_register_config);
}


static ssize_t max6875_write(struct kobject *kobj, char *buf, loff_t off, size_t count,
			     enum max6875_area_type area_type)
{
	struct i2c_client *client = to_i2c_client(container_of(kobj, struct device, kobj));
	struct max6875_data *data = i2c_get_clientdata(client);
	struct eeprom_block *blk;
	int slice, addr, retval;
	ssize_t sent = 0;

	blk = &data->blocks[area_type];

	if (off > blk->size)
		return 0;
	if ((off + count) > blk->size)
		count = blk->size - off;

	if (down_interruptible(&data->update_lock))
		return -EAGAIN;

	/* writing to a register is done with i2c_smbus_write_byte_data() */
	if (blk->type == max6875_register_config) {
		for (sent = 0; sent < count; sent++) {
			addr = off + sent;
			if (addr == 0x44)
				continue;

			retval = i2c_smbus_write_byte_data(client, addr, buf[sent]);
		}
	} else {
		int cmd, val;

		/* We are writing to EEPROM */
		for (sent = 0; sent < count; sent++) {
			addr = blk->base + off + sent;
			cmd = addr >> 8;
			val = (addr & 0xff) | (buf[sent] << 8);	// reversed

			if (addr == 0x8044)
				continue;

			retval = i2c_smbus_write_word_data(client, cmd, val);

			if (retval) {
				goto error_exit;
			}

			/* A write takes up to 11 ms */
			msleep(11);
		}
	}

	/* Invalidate the scratch buffer */
	for (slice = (off >> SLICE_BITS); slice <= ((off + count - 1) >> SLICE_BITS); slice++)
		blk->valid &= ~(1 << slice);

	error_exit:
	up(&data->update_lock);

	return sent;
}

static ssize_t max6875_user_write(struct kobject *kobj, char *buf, loff_t off, size_t count)
{
	return max6875_write(kobj, buf, off, count, max6875_eeprom_user);
}

static ssize_t max6875_config_write(struct kobject *kobj, char *buf, loff_t off, size_t count)
{
	return max6875_write(kobj, buf, off, count, max6875_eeprom_config);
}

static ssize_t max6875_cfgreg_write(struct kobject *kobj, char *buf, loff_t off, size_t count)
{
	return max6875_write(kobj, buf, off, count, max6875_register_config);
}

static struct bin_attribute user_eeprom_attr = {
	.attr = {
		.name = "eeprom_user",
		.mode = S_IRUGO | S_IWUSR | S_IWGRP,
		.owner = THIS_MODULE,
	},
	.size  = USER_EEPROM_SIZE,
	.read  = max6875_user_read,
	.write = max6875_user_write,
};

static struct bin_attribute config_eeprom_attr = {
	.attr = {
		.name = "eeprom_config",
		.mode = S_IRUGO | S_IWUSR,
		.owner = THIS_MODULE,
	},
	.size  = CONFIG_EEPROM_SIZE,
	.read  = max6875_config_read,
	.write = max6875_config_write,
};

static struct bin_attribute config_register_attr = {
	.attr = {
		.name = "reg_config",
		.mode = S_IRUGO | S_IWUSR,
		.owner = THIS_MODULE,
	},
	.size  = CONFIG_EEPROM_SIZE,
	.read  = max6875_cfgreg_read,
	.write = max6875_cfgreg_write,
};

static int max6875_attach_adapter(struct i2c_adapter *adapter)
{
	return i2c_detect(adapter, &addr_data, max6875_detect);
}

/* This function is called by i2c_detect */
static int max6875_detect(struct i2c_adapter *adapter, int address, int kind)
{
	struct i2c_client *new_client;
	struct max6875_data *data;
	int err = 0;

	/* Prevent 24RF08 corruption (in case of user error) */
	if (kind < 0)
		i2c_smbus_xfer(adapter, address, 0, 0, 0,
			       I2C_SMBUS_QUICK, NULL);

	/* There are three ways we can read the EEPROM data:
	   (1) I2C block reads (faster, but unsupported by most adapters)
	   (2) Consecutive byte reads (100% overhead)
	   (3) Regular byte data reads (200% overhead)
	   The third method is not implemented by this driver because all
	   known adapters support at least the second. */
	if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_READ_BYTE_DATA |
				     I2C_FUNC_SMBUS_BYTE |
				     I2C_FUNC_SMBUS_WRITE_BYTE_DATA))
		goto exit;

	/* OK. For now, we presume we have a valid client. We now create the
	   client structure, even though we cannot fill it completely yet.
	   But it allows us to access eeprom_{read,write}_value. */
	if (!(data = kmalloc(sizeof(struct max6875_data), GFP_KERNEL))) {
		err = -ENOMEM;
		goto exit;
	}
	memset(data, 0, sizeof(struct max6875_data));

	new_client = &data->client;
	i2c_set_clientdata(new_client, data);
	new_client->addr = address;
	new_client->adapter = adapter;
	new_client->driver = &max6875_driver;
	new_client->flags = 0;

	/* Setup the user section */
	data->blocks[max6875_eeprom_user].type    = max6875_eeprom_user;
	data->blocks[max6875_eeprom_user].slices  = USER_EEPROM_SLICES;
	data->blocks[max6875_eeprom_user].size    = USER_EEPROM_SIZE;
	data->blocks[max6875_eeprom_user].base    = USER_EEPROM_BASE;
	data->blocks[max6875_eeprom_user].data    = data->data;
	data->blocks[max6875_eeprom_user].updated = data->last_updated;

	/* Setup the config section */
	data->blocks[max6875_eeprom_config].type    = max6875_eeprom_config;
	data->blocks[max6875_eeprom_config].slices  = CONFIG_EEPROM_SLICES;
	data->blocks[max6875_eeprom_config].size    = CONFIG_EEPROM_SIZE;
	data->blocks[max6875_eeprom_config].base    = CONFIG_EEPROM_BASE;
	data->blocks[max6875_eeprom_config].data    = &data->data[USER_EEPROM_SIZE];
	data->blocks[max6875_eeprom_config].updated = &data->last_updated[USER_EEPROM_SLICES];

	/* Setup the register section */
	data->blocks[max6875_register_config].type    = max6875_register_config;
	data->blocks[max6875_register_config].slices  = CONFIG_EEPROM_SLICES;
	data->blocks[max6875_register_config].size    = CONFIG_EEPROM_SIZE;
	data->blocks[max6875_register_config].base    = 0;
	data->blocks[max6875_register_config].data    = &data->data[USER_EEPROM_SIZE+CONFIG_EEPROM_SIZE];
	data->blocks[max6875_register_config].updated = &data->last_updated[USER_EEPROM_SLICES+CONFIG_EEPROM_SLICES];

	/* Init the data */
	memset(data->data, 0xff, sizeof(data->data));

	/* Fill in the remaining client fields */
	strlcpy(new_client->name, "max6875", I2C_NAME_SIZE);
	init_MUTEX(&data->update_lock);

	/* Verify that the chip is really what we think it is */
	if ((max6875_update_slice(new_client, &data->blocks[max6875_eeprom_config], 4) < 0) ||
	    (max6875_update_slice(new_client, &data->blocks[max6875_register_config], 4) < 0))
		goto exit_kfree;

	/* 0x41,0x42 must be zero and 0x40 must match in eeprom and registers */
	if ((data->blocks[max6875_eeprom_config].data[0x41] != 0) ||
	    (data->blocks[max6875_eeprom_config].data[0x42] != 0) ||
	    (data->blocks[max6875_register_config].data[0x41] != 0) ||
	    (data->blocks[max6875_register_config].data[0x42] != 0) ||
	    (data->blocks[max6875_eeprom_config].data[0x40] !=
	     data->blocks[max6875_register_config].data[0x40]))
		goto exit_kfree;

	/* Tell the I2C layer a new client has arrived */
	if ((err = i2c_attach_client(new_client)))
		goto exit_kfree;

	/* create the sysfs eeprom files with the correct permissions */
	if (allow_write == 0) {
		user_eeprom_attr.attr.mode &= ~S_IWUGO;
		user_eeprom_attr.write = NULL;
		config_eeprom_attr.attr.mode &= ~S_IWUGO;
		config_eeprom_attr.write = NULL;
		config_register_attr.attr.mode &= ~S_IWUGO;
		config_register_attr.write = NULL;
	}
	sysfs_create_bin_file(&new_client->dev.kobj, &user_eeprom_attr);
	sysfs_create_bin_file(&new_client->dev.kobj, &config_eeprom_attr);
	sysfs_create_bin_file(&new_client->dev.kobj, &config_register_attr);

	return 0;

exit_kfree:
	kfree(data);
exit:
	return err;
}

static int max6875_detach_client(struct i2c_client *client)
{
	int err;

	err = i2c_detach_client(client);
	if (err) {
		dev_err(&client->dev, "Client deregistration failed, client not detached.\n");
		return err;
	}

	kfree(i2c_get_clientdata(client));

	return 0;
}

static int __init max6875_init(void)
{
	return i2c_add_driver(&max6875_driver);
}

static void __exit max6875_exit(void)
{
	i2c_del_driver(&max6875_driver);
}


MODULE_AUTHOR("Ben Gardner <bgardner@wabtec.com>");
MODULE_DESCRIPTION("MAX6875 driver");
MODULE_LICENSE("GPL");

module_init(max6875_init);
module_exit(max6875_exit);