1/*
2    max6875.c - driver for MAX6874/MAX6875
3
4    Copyright (C) 2005 Ben Gardner <bgardner@wabtec.com>
5
6    Based on i2c/chips/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/init.h>
31#include <linux/module.h>
32#include <linux/slab.h>
33#include <linux/i2c.h>
34#include <linux/mutex.h>
35
36/* Do not scan - the MAX6875 access method will write to some EEPROM chips */
37static unsigned short normal_i2c[] = {I2C_CLIENT_END};
38
39/* Insmod parameters */
40I2C_CLIENT_INSMOD_1(max6875);
41
42/* The MAX6875 can only read/write 16 bytes at a time */
43#define SLICE_SIZE			16
44#define SLICE_BITS			4
45
46/* USER EEPROM is at addresses 0x8100 - 0x82FF */
47#define USER_EEPROM_BASE		0x8100
48#define USER_EEPROM_SIZE		0x0200
49#define USER_EEPROM_SLICES		32
50
51/* MAX6875 commands */
52#define MAX6875_CMD_BLK_READ		0x84
53
54/* Each client has this additional data */
55struct max6875_data {
56	struct i2c_client	client;
57	struct mutex		update_lock;
58
59	u32			valid;
60	u8			data[USER_EEPROM_SIZE];
61	unsigned long		last_updated[USER_EEPROM_SLICES];
62};
63
64static int max6875_attach_adapter(struct i2c_adapter *adapter);
65static int max6875_detect(struct i2c_adapter *adapter, int address, int kind);
66static int max6875_detach_client(struct i2c_client *client);
67
68/* This is the driver that will be inserted */
69static struct i2c_driver max6875_driver = {
70	.driver = {
71		.name	= "max6875",
72	},
73	.attach_adapter	= max6875_attach_adapter,
74	.detach_client	= max6875_detach_client,
75};
76
77static void max6875_update_slice(struct i2c_client *client, int slice)
78{
79	struct max6875_data *data = i2c_get_clientdata(client);
80	int i, j, addr;
81	u8 *buf;
82
83	if (slice >= USER_EEPROM_SLICES)
84		return;
85
86	mutex_lock(&data->update_lock);
87
88	buf = &data->data[slice << SLICE_BITS];
89
90	if (!(data->valid & (1 << slice)) ||
91	    time_after(jiffies, data->last_updated[slice])) {
92
93		dev_dbg(&client->dev, "Starting update of slice %u\n", slice);
94
95		data->valid &= ~(1 << slice);
96
97		addr = USER_EEPROM_BASE + (slice << SLICE_BITS);
98
99		/* select the eeprom address */
100		if (i2c_smbus_write_byte_data(client, addr >> 8, addr & 0xFF)) {
101			dev_err(&client->dev, "address set failed\n");
102			goto exit_up;
103		}
104
105		if (i2c_check_functionality(client->adapter,
106					    I2C_FUNC_SMBUS_READ_I2C_BLOCK)) {
107			if (i2c_smbus_read_i2c_block_data(client,
108							  MAX6875_CMD_BLK_READ,
109							  buf) != SLICE_SIZE) {
110				goto exit_up;
111			}
112		} else {
113			for (i = 0; i < SLICE_SIZE; i++) {
114				j = i2c_smbus_read_byte(client);
115				if (j < 0) {
116					goto exit_up;
117				}
118				buf[i] = j;
119			}
120		}
121		data->last_updated[slice] = jiffies;
122		data->valid |= (1 << slice);
123	}
124exit_up:
125	mutex_unlock(&data->update_lock);
126}
127
128static ssize_t max6875_read(struct kobject *kobj, char *buf, loff_t off,
129			    size_t count)
130{
131	struct i2c_client *client = kobj_to_i2c_client(kobj);
132	struct max6875_data *data = i2c_get_clientdata(client);
133	int slice, max_slice;
134
135	if (off > USER_EEPROM_SIZE)
136		return 0;
137
138	if (off + count > USER_EEPROM_SIZE)
139		count = USER_EEPROM_SIZE - off;
140
141	/* refresh slices which contain requested bytes */
142	max_slice = (off + count - 1) >> SLICE_BITS;
143	for (slice = (off >> SLICE_BITS); slice <= max_slice; slice++)
144		max6875_update_slice(client, slice);
145
146	memcpy(buf, &data->data[off], count);
147
148	return count;
149}
150
151static struct bin_attribute user_eeprom_attr = {
152	.attr = {
153		.name = "eeprom",
154		.mode = S_IRUGO,
155		.owner = THIS_MODULE,
156	},
157	.size = USER_EEPROM_SIZE,
158	.read = max6875_read,
159};
160
161static int max6875_attach_adapter(struct i2c_adapter *adapter)
162{
163	return i2c_probe(adapter, &addr_data, max6875_detect);
164}
165
166/* This function is called by i2c_probe */
167static int max6875_detect(struct i2c_adapter *adapter, int address, int kind)
168{
169	struct i2c_client *real_client;
170	struct i2c_client *fake_client;
171	struct max6875_data *data;
172	int err = 0;
173
174	if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_WRITE_BYTE_DATA
175				     | I2C_FUNC_SMBUS_READ_BYTE))
176		return 0;
177
178	/* Only check even addresses */
179	if (address & 1)
180		return 0;
181
182	if (!(data = kzalloc(sizeof(struct max6875_data), GFP_KERNEL)))
183		return -ENOMEM;
184
185	/* A fake client is created on the odd address */
186	if (!(fake_client = kzalloc(sizeof(struct i2c_client), GFP_KERNEL))) {
187		err = -ENOMEM;
188		goto exit_kfree1;
189	}
190
191	/* Init real i2c_client */
192	real_client = &data->client;
193	i2c_set_clientdata(real_client, data);
194	real_client->addr = address;
195	real_client->adapter = adapter;
196	real_client->driver = &max6875_driver;
197	real_client->flags = 0;
198	strlcpy(real_client->name, "max6875", I2C_NAME_SIZE);
199	mutex_init(&data->update_lock);
200
201	/* Init fake client data */
202	i2c_set_clientdata(fake_client, NULL);
203	fake_client->addr = address | 1;
204	fake_client->adapter = adapter;
205	fake_client->driver = &max6875_driver;
206	fake_client->flags = 0;
207	strlcpy(fake_client->name, "max6875 subclient", I2C_NAME_SIZE);
208
209	/* Prevent 24RF08 corruption (in case of user error) */
210	i2c_smbus_write_quick(real_client, 0);
211
212	if ((err = i2c_attach_client(real_client)) != 0)
213		goto exit_kfree2;
214
215	if ((err = i2c_attach_client(fake_client)) != 0)
216		goto exit_detach1;
217
218	err = sysfs_create_bin_file(&real_client->dev.kobj, &user_eeprom_attr);
219	if (err)
220		goto exit_detach2;
221
222	return 0;
223
224exit_detach2:
225	i2c_detach_client(fake_client);
226exit_detach1:
227	i2c_detach_client(real_client);
228exit_kfree2:
229	kfree(fake_client);
230exit_kfree1:
231	kfree(data);
232	return err;
233}
234
235/* Will be called for both the real client and the fake client */
236static int max6875_detach_client(struct i2c_client *client)
237{
238	int err;
239	struct max6875_data *data = i2c_get_clientdata(client);
240
241	/* data is NULL for the fake client */
242	if (data)
243		sysfs_remove_bin_file(&client->dev.kobj, &user_eeprom_attr);
244
245	err = i2c_detach_client(client);
246	if (err)
247		return err;
248
249	if (data)		/* real client */
250		kfree(data);
251	else			/* fake client */
252		kfree(client);
253	return 0;
254}
255
256static int __init max6875_init(void)
257{
258	return i2c_add_driver(&max6875_driver);
259}
260
261static void __exit max6875_exit(void)
262{
263	i2c_del_driver(&max6875_driver);
264}
265
266
267MODULE_AUTHOR("Ben Gardner <bgardner@wabtec.com>");
268MODULE_DESCRIPTION("MAX6875 driver");
269MODULE_LICENSE("GPL");
270
271module_init(max6875_init);
272module_exit(max6875_exit);
273