aboutsummaryrefslogtreecommitdiff
path: root/drivers/i2c/chips/max6875.c
blob: 31cee2d34a17ede7ce86ac96eb5ee0dd845c4594 (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
/*
    max6875.c - driver for MAX6874/MAX6875

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

    Based on i2c/chips/eeprom.c

    The MAX6875 has a bank of registers and two banks of EEPROM.
    Address ranges are defined as follows:
     * 0x0000 - 0x0046 = configuration registers
     * 0x8000 - 0x8046 = configuration EEPROM
     * 0x8100 - 0x82FF = user EEPROM

    This driver makes the user EEPROM available for read.

    The registers & config EEPROM should be accessed via i2c-dev.

    The MAX6875 ignores the lowest address bit, so each chip responds to
    two addresses - 0x50/0x51 and 0x52/0x53.

    Note that the MAX6875 uses i2c_smbus_write_byte_data() to set the read
    address, so this driver is destructive if loaded for the wrong EEPROM chip.

    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/kernel.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/i2c.h>
#include <asm/semaphore.h>

/* Do not scan - the MAX6875 access method will write to some EEPROM chips */
static unsigned short normal_i2c[] = {I2C_CLIENT_END};

/* Insmod parameters */
I2C_CLIENT_INSMOD_1(max6875);

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

/* 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_BLK_READ		0x84

/* Each client has this additional data */
struct max6875_data {
	struct i2c_client	client;
	struct semaphore	update_lock;

	u32			valid;
	u8			data[USER_EEPROM_SIZE];
	unsigned long		last_updated[USER_EEPROM_SLICES];
};

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 void max6875_update_slice(struct i2c_client *client, int slice)
{
	struct max6875_data *data = i2c_get_clientdata(client);
	int i, j, addr;
	u8 *buf;

	if (slice >= USER_EEPROM_SLICES)
		return;

	down(&data->update_lock);

	buf = &data->data[slice << SLICE_BITS];

	if (!(data->valid & (1 << slice)) ||
	    time_after(jiffies, data->last_updated[slice])) {

		dev_dbg(&client->dev, "Starting update of slice %u\n", slice);

		data->valid &= ~(1 << slice);

		addr = USER_EEPROM_BASE + (slice << SLICE_BITS);

		/* select the eeprom address */
		if (i2c_smbus_write_byte_data(client, addr >> 8, addr & 0xFF)) {
			dev_err(&client->dev, "address set failed\n");
			goto exit_up;
		}

		if (i2c_check_functionality(client->adapter,
					    I2C_FUNC_SMBUS_READ_I2C_BLOCK)) {
			if (i2c_smbus_read_i2c_block_data(client,
							  MAX6875_CMD_BLK_READ,
							  buf) != SLICE_SIZE) {
				goto exit_up;
			}
		} else {
			for (i = 0; i < SLICE_SIZE; i++) {
				j = i2c_smbus_read_byte(client);
				if (j < 0) {
					goto exit_up;
				}
				buf[i] = j;
			}
		}
		data->last_updated[slice] = jiffies;
		data->valid |= (1 << slice);
	}
exit_up:
	up(&data->update_lock);
}

static ssize_t max6875_read(struct kobject *kobj, char *buf, loff_t off,
			    size_t count)
{
	struct i2c_client *client = kobj_to_i2c_client(kobj);
	struct max6875_data *data = i2c_get_clientdata(client);
	int slice, max_slice;

	if (off > USER_EEPROM_SIZE)
		return 0;

	if (off + count > USER_EEPROM_SIZE)
		count = USER_EEPROM_SIZE - off;

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

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

	return count;
}

static struct bin_attribute user_eeprom_attr = {
	.attr = {
		.name = "eeprom",
		.mode = S_IRUGO,
		.owner = THIS_MODULE,
	},
	.size = USER_EEPROM_SIZE,
	.read = max6875_read,
};

static int max6875_attach_adapter(struct i2c_adapter *adapter)
{
	return i2c_probe(adapter, &addr_data, max6875_detect);
}

/* This function is called by i2c_probe */
static int max6875_detect(struct i2c_adapter *adapter, int address, int kind)
{
	struct i2c_client *real_client;
	struct i2c_client *fake_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);

	if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_WRITE_BYTE_DATA
				     | I2C_FUNC_SMBUS_READ_BYTE))
		return 0;

	/* Only check even addresses */
	if (address & 1)
		return 0;

	if (!(data = kmalloc(sizeof(struct max6875_data), GFP_KERNEL)))
		return -ENOMEM;
	memset(data, 0, sizeof(struct max6875_data));

	/* A fake client is created on the odd address */
	if (!(fake_client = kmalloc(sizeof(struct i2c_client), GFP_KERNEL))) {
		err = -ENOMEM;
		goto exit_kfree1;
	}
	memset(fake_client, 0, sizeof(struct i2c_client));

	/* Init real i2c_client */
	real_client = &data->client;
	i2c_set_clientdata(real_client, data);
	real_client->addr = address;
	real_client->adapter = adapter;
	real_client->driver = &max6875_driver;
	real_client->flags = 0;
	strlcpy(real_client->name, "max6875", I2C_NAME_SIZE);
	init_MUTEX(&data->update_lock);

	/* Init fake client data */
	/* set the client data to the i2c_client so that it will get freed */
	i2c_set_clientdata(fake_client, fake_client);
	fake_client->addr = address | 1;
	fake_client->adapter = adapter;
	fake_client->driver = &max6875_driver;
	fake_client->flags = 0;
	strlcpy(fake_client->name, "max6875 subclient", I2C_NAME_SIZE);

	/* Prevent 24RF08 corruption (in case of user error) */
	i2c_smbus_write_quick(real_client, 0);

	if ((err = i2c_attach_client(real_client)) != 0)
		goto exit_kfree2;

	if ((err = i2c_attach_client(fake_client)) != 0)
		goto exit_detach;

	sysfs_create_bin_file(&real_client->dev.kobj, &user_eeprom_attr);

	return 0;

exit_detach:
	i2c_detach_client(real_client);
exit_kfree2:
	kfree(fake_client);
exit_kfree1:
	kfree(data);
	return err;
}

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

	err = i2c_detach_client(client);
	if (err)
		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);