1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * max6875.c - driver for MAX6874/MAX6875 4 * 5 * Copyright (C) 2005 Ben Gardner <bgardner@wabtec.com> 6 * 7 * Based on eeprom.c 8 * 9 * The MAX6875 has a bank of registers and two banks of EEPROM. 10 * Address ranges are defined as follows: 11 * * 0x0000 - 0x0046 = configuration registers 12 * * 0x8000 - 0x8046 = configuration EEPROM 13 * * 0x8100 - 0x82FF = user EEPROM 14 * 15 * This driver makes the user EEPROM available for read. 16 * 17 * The registers & config EEPROM should be accessed via i2c-dev. 18 * 19 * The MAX6875 ignores the lowest address bit, so each chip responds to 20 * two addresses - 0x50/0x51 and 0x52/0x53. 21 * 22 * Note that the MAX6875 uses i2c_smbus_write_byte_data() to set the read 23 * address, so this driver is destructive if loaded for the wrong EEPROM chip. 24 */ 25 26 #include <linux/kernel.h> 27 #include <linux/module.h> 28 #include <linux/slab.h> 29 #include <linux/i2c.h> 30 #include <linux/mutex.h> 31 32 /* The MAX6875 can only read/write 16 bytes at a time */ 33 #define SLICE_SIZE 16 34 #define SLICE_BITS 4 35 36 /* USER EEPROM is at addresses 0x8100 - 0x82FF */ 37 #define USER_EEPROM_BASE 0x8100 38 #define USER_EEPROM_SIZE 0x0200 39 #define USER_EEPROM_SLICES 32 40 41 /* MAX6875 commands */ 42 #define MAX6875_CMD_BLK_READ 0x84 43 44 /* Each client has this additional data */ 45 struct max6875_data { 46 struct i2c_client *fake_client; 47 struct mutex update_lock; 48 49 u32 valid; 50 u8 data[USER_EEPROM_SIZE]; 51 unsigned long last_updated[USER_EEPROM_SLICES]; 52 }; 53 54 static void max6875_update_slice(struct i2c_client *client, int slice) 55 { 56 struct max6875_data *data = i2c_get_clientdata(client); 57 int i, j, addr; 58 u8 *buf; 59 60 if (slice >= USER_EEPROM_SLICES) 61 return; 62 63 mutex_lock(&data->update_lock); 64 65 buf = &data->data[slice << SLICE_BITS]; 66 67 if (!(data->valid & (1 << slice)) || 68 time_after(jiffies, data->last_updated[slice])) { 69 70 dev_dbg(&client->dev, "Starting update of slice %u\n", slice); 71 72 data->valid &= ~(1 << slice); 73 74 addr = USER_EEPROM_BASE + (slice << SLICE_BITS); 75 76 /* select the eeprom address */ 77 if (i2c_smbus_write_byte_data(client, addr >> 8, addr & 0xFF)) { 78 dev_err(&client->dev, "address set failed\n"); 79 goto exit_up; 80 } 81 82 if (i2c_check_functionality(client->adapter, 83 I2C_FUNC_SMBUS_READ_I2C_BLOCK)) { 84 if (i2c_smbus_read_i2c_block_data(client, 85 MAX6875_CMD_BLK_READ, 86 SLICE_SIZE, 87 buf) != SLICE_SIZE) { 88 goto exit_up; 89 } 90 } else { 91 for (i = 0; i < SLICE_SIZE; i++) { 92 j = i2c_smbus_read_byte(client); 93 if (j < 0) { 94 goto exit_up; 95 } 96 buf[i] = j; 97 } 98 } 99 data->last_updated[slice] = jiffies; 100 data->valid |= (1 << slice); 101 } 102 exit_up: 103 mutex_unlock(&data->update_lock); 104 } 105 106 static ssize_t max6875_read(struct file *filp, struct kobject *kobj, 107 struct bin_attribute *bin_attr, 108 char *buf, loff_t off, size_t count) 109 { 110 struct i2c_client *client = kobj_to_i2c_client(kobj); 111 struct max6875_data *data = i2c_get_clientdata(client); 112 int slice, max_slice; 113 114 /* refresh slices which contain requested bytes */ 115 max_slice = (off + count - 1) >> SLICE_BITS; 116 for (slice = (off >> SLICE_BITS); slice <= max_slice; slice++) 117 max6875_update_slice(client, slice); 118 119 memcpy(buf, &data->data[off], count); 120 121 return count; 122 } 123 124 static const struct bin_attribute user_eeprom_attr = { 125 .attr = { 126 .name = "eeprom", 127 .mode = S_IRUGO, 128 }, 129 .size = USER_EEPROM_SIZE, 130 .read = max6875_read, 131 }; 132 133 static int max6875_probe(struct i2c_client *client) 134 { 135 struct i2c_adapter *adapter = client->adapter; 136 struct max6875_data *data; 137 int err; 138 139 if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_WRITE_BYTE_DATA 140 | I2C_FUNC_SMBUS_READ_BYTE)) 141 return -ENODEV; 142 143 /* Only bind to even addresses */ 144 if (client->addr & 1) 145 return -ENODEV; 146 147 data = kzalloc(sizeof(struct max6875_data), GFP_KERNEL); 148 if (!data) 149 return -ENOMEM; 150 151 /* A fake client is created on the odd address */ 152 data->fake_client = i2c_new_dummy_device(client->adapter, client->addr + 1); 153 if (IS_ERR(data->fake_client)) { 154 err = PTR_ERR(data->fake_client); 155 goto exit_kfree; 156 } 157 158 /* Init real i2c_client */ 159 i2c_set_clientdata(client, data); 160 mutex_init(&data->update_lock); 161 162 err = sysfs_create_bin_file(&client->dev.kobj, &user_eeprom_attr); 163 if (err) 164 goto exit_remove_fake; 165 166 return 0; 167 168 exit_remove_fake: 169 i2c_unregister_device(data->fake_client); 170 exit_kfree: 171 kfree(data); 172 return err; 173 } 174 175 static void max6875_remove(struct i2c_client *client) 176 { 177 struct max6875_data *data = i2c_get_clientdata(client); 178 179 i2c_unregister_device(data->fake_client); 180 181 sysfs_remove_bin_file(&client->dev.kobj, &user_eeprom_attr); 182 kfree(data); 183 } 184 185 static const struct i2c_device_id max6875_id[] = { 186 { "max6875", 0 }, 187 { } 188 }; 189 MODULE_DEVICE_TABLE(i2c, max6875_id); 190 191 static struct i2c_driver max6875_driver = { 192 .driver = { 193 .name = "max6875", 194 }, 195 .probe_new = max6875_probe, 196 .remove = max6875_remove, 197 .id_table = max6875_id, 198 }; 199 200 module_i2c_driver(max6875_driver); 201 202 MODULE_AUTHOR("Ben Gardner <bgardner@wabtec.com>"); 203 MODULE_DESCRIPTION("MAX6875 driver"); 204 MODULE_LICENSE("GPL"); 205