1/*
2 * max6875.c - driver for MAX6874/MAX6875
3 *
4 * Copyright (C) 2005 Ben Gardner <bgardner@wabtec.com>
5 *
6 * Based on eeprom.c
7 *
8 * The MAX6875 has a bank of registers and two banks of EEPROM.
9 * Address ranges are defined as follows:
10 *  * 0x0000 - 0x0046 = configuration registers
11 *  * 0x8000 - 0x8046 = configuration EEPROM
12 *  * 0x8100 - 0x82FF = user EEPROM
13 *
14 * This driver makes the user EEPROM available for read.
15 *
16 * The registers & config EEPROM should be accessed via i2c-dev.
17 *
18 * The MAX6875 ignores the lowest address bit, so each chip responds to
19 * two addresses - 0x50/0x51 and 0x52/0x53.
20 *
21 * Note that the MAX6875 uses i2c_smbus_write_byte_data() to set the read
22 * address, so this driver is destructive if loaded for the wrong EEPROM chip.
23 *
24 * This program is free software; you can redistribute it and/or modify
25 * it under the terms of the GNU General Public License as published by
26 * the Free Software Foundation; version 2 of the License.
27 */
28
29#include <linux/kernel.h>
30#include <linux/module.h>
31#include <linux/slab.h>
32#include <linux/i2c.h>
33#include <linux/mutex.h>
34
35/* The MAX6875 can only read/write 16 bytes at a time */
36#define SLICE_SIZE			16
37#define SLICE_BITS			4
38
39/* USER EEPROM is at addresses 0x8100 - 0x82FF */
40#define USER_EEPROM_BASE		0x8100
41#define USER_EEPROM_SIZE		0x0200
42#define USER_EEPROM_SLICES		32
43
44/* MAX6875 commands */
45#define MAX6875_CMD_BLK_READ		0x84
46
47/* Each client has this additional data */
48struct max6875_data {
49	struct i2c_client	*fake_client;
50	struct mutex		update_lock;
51
52	u32			valid;
53	u8			data[USER_EEPROM_SIZE];
54	unsigned long		last_updated[USER_EEPROM_SLICES];
55};
56
57static void max6875_update_slice(struct i2c_client *client, int slice)
58{
59	struct max6875_data *data = i2c_get_clientdata(client);
60	int i, j, addr;
61	u8 *buf;
62
63	if (slice >= USER_EEPROM_SLICES)
64		return;
65
66	mutex_lock(&data->update_lock);
67
68	buf = &data->data[slice << SLICE_BITS];
69
70	if (!(data->valid & (1 << slice)) ||
71	    time_after(jiffies, data->last_updated[slice])) {
72
73		dev_dbg(&client->dev, "Starting update of slice %u\n", slice);
74
75		data->valid &= ~(1 << slice);
76
77		addr = USER_EEPROM_BASE + (slice << SLICE_BITS);
78
79		/* select the eeprom address */
80		if (i2c_smbus_write_byte_data(client, addr >> 8, addr & 0xFF)) {
81			dev_err(&client->dev, "address set failed\n");
82			goto exit_up;
83		}
84
85		if (i2c_check_functionality(client->adapter,
86					    I2C_FUNC_SMBUS_READ_I2C_BLOCK)) {
87			if (i2c_smbus_read_i2c_block_data(client,
88							  MAX6875_CMD_BLK_READ,
89							  SLICE_SIZE,
90							  buf) != SLICE_SIZE) {
91				goto exit_up;
92			}
93		} else {
94			for (i = 0; i < SLICE_SIZE; i++) {
95				j = i2c_smbus_read_byte(client);
96				if (j < 0) {
97					goto exit_up;
98				}
99				buf[i] = j;
100			}
101		}
102		data->last_updated[slice] = jiffies;
103		data->valid |= (1 << slice);
104	}
105exit_up:
106	mutex_unlock(&data->update_lock);
107}
108
109static ssize_t max6875_read(struct file *filp, struct kobject *kobj,
110			    struct bin_attribute *bin_attr,
111			    char *buf, loff_t off, size_t count)
112{
113	struct i2c_client *client = kobj_to_i2c_client(kobj);
114	struct max6875_data *data = i2c_get_clientdata(client);
115	int slice, max_slice;
116
117	/* refresh slices which contain requested bytes */
118	max_slice = (off + count - 1) >> SLICE_BITS;
119	for (slice = (off >> SLICE_BITS); slice <= max_slice; slice++)
120		max6875_update_slice(client, slice);
121
122	memcpy(buf, &data->data[off], count);
123
124	return count;
125}
126
127static struct bin_attribute user_eeprom_attr = {
128	.attr = {
129		.name = "eeprom",
130		.mode = S_IRUGO,
131	},
132	.size = USER_EEPROM_SIZE,
133	.read = max6875_read,
134};
135
136static int max6875_probe(struct i2c_client *client,
137			 const struct i2c_device_id *id)
138{
139	struct i2c_adapter *adapter = client->adapter;
140	struct max6875_data *data;
141	int err;
142
143	if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_WRITE_BYTE_DATA
144				     | I2C_FUNC_SMBUS_READ_BYTE))
145		return -ENODEV;
146
147	/* Only bind to even addresses */
148	if (client->addr & 1)
149		return -ENODEV;
150
151	if (!(data = kzalloc(sizeof(struct max6875_data), GFP_KERNEL)))
152		return -ENOMEM;
153
154	/* A fake client is created on the odd address */
155	data->fake_client = i2c_new_dummy(client->adapter, client->addr + 1);
156	if (!data->fake_client) {
157		err = -ENOMEM;
158		goto exit_kfree;
159	}
160
161	/* Init real i2c_client */
162	i2c_set_clientdata(client, data);
163	mutex_init(&data->update_lock);
164
165	err = sysfs_create_bin_file(&client->dev.kobj, &user_eeprom_attr);
166	if (err)
167		goto exit_remove_fake;
168
169	return 0;
170
171exit_remove_fake:
172	i2c_unregister_device(data->fake_client);
173exit_kfree:
174	kfree(data);
175	return err;
176}
177
178static int max6875_remove(struct i2c_client *client)
179{
180	struct max6875_data *data = i2c_get_clientdata(client);
181
182	i2c_unregister_device(data->fake_client);
183
184	sysfs_remove_bin_file(&client->dev.kobj, &user_eeprom_attr);
185	kfree(data);
186
187	return 0;
188}
189
190static const struct i2c_device_id max6875_id[] = {
191	{ "max6875", 0 },
192	{ }
193};
194MODULE_DEVICE_TABLE(i2c, max6875_id);
195
196static struct i2c_driver max6875_driver = {
197	.driver = {
198		.name	= "max6875",
199	},
200	.probe		= max6875_probe,
201	.remove		= max6875_remove,
202	.id_table	= max6875_id,
203};
204
205module_i2c_driver(max6875_driver);
206
207MODULE_AUTHOR("Ben Gardner <bgardner@wabtec.com>");
208MODULE_DESCRIPTION("MAX6875 driver");
209MODULE_LICENSE("GPL");
210