diff options
Diffstat (limited to 'drivers/misc/eeprom/max6875.c')
| -rw-r--r-- | drivers/misc/eeprom/max6875.c | 207 |
1 files changed, 207 insertions, 0 deletions
diff --git a/drivers/misc/eeprom/max6875.c b/drivers/misc/eeprom/max6875.c new file mode 100644 index 000000000..9da81f6d4 --- /dev/null +++ b/drivers/misc/eeprom/max6875.c @@ -0,0 +1,207 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * max6875.c - driver for MAX6874/MAX6875 + * + * Copyright (C) 2005 Ben Gardner <bgardner@wabtec.com> + * + * Based on 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. + */ + +#include <linux/kernel.h> +#include <linux/module.h> +#include <linux/slab.h> +#include <linux/i2c.h> +#include <linux/mutex.h> + +/* 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 *fake_client; + struct mutex update_lock; + + u32 valid; + u8 data[USER_EEPROM_SIZE]; + unsigned long last_updated[USER_EEPROM_SLICES]; +}; + +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; + + mutex_lock(&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, + SLICE_SIZE, + 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: + mutex_unlock(&data->update_lock); +} + +static ssize_t max6875_read(struct file *filp, struct kobject *kobj, + struct bin_attribute *bin_attr, + 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; + + /* 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 const struct bin_attribute user_eeprom_attr = { + .attr = { + .name = "eeprom", + .mode = S_IRUGO, + }, + .size = USER_EEPROM_SIZE, + .read = max6875_read, +}; + +static int max6875_probe(struct i2c_client *client, + const struct i2c_device_id *id) +{ + struct i2c_adapter *adapter = client->adapter; + struct max6875_data *data; + int err; + + if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_WRITE_BYTE_DATA + | I2C_FUNC_SMBUS_READ_BYTE)) + return -ENODEV; + + /* Only bind to even addresses */ + if (client->addr & 1) + return -ENODEV; + + data = kzalloc(sizeof(struct max6875_data), GFP_KERNEL); + if (!data) + return -ENOMEM; + + /* A fake client is created on the odd address */ + data->fake_client = i2c_new_dummy_device(client->adapter, client->addr + 1); + if (IS_ERR(data->fake_client)) { + err = PTR_ERR(data->fake_client); + goto exit_kfree; + } + + /* Init real i2c_client */ + i2c_set_clientdata(client, data); + mutex_init(&data->update_lock); + + err = sysfs_create_bin_file(&client->dev.kobj, &user_eeprom_attr); + if (err) + goto exit_remove_fake; + + return 0; + +exit_remove_fake: + i2c_unregister_device(data->fake_client); +exit_kfree: + kfree(data); + return err; +} + +static int max6875_remove(struct i2c_client *client) +{ + struct max6875_data *data = i2c_get_clientdata(client); + + i2c_unregister_device(data->fake_client); + + sysfs_remove_bin_file(&client->dev.kobj, &user_eeprom_attr); + kfree(data); + + return 0; +} + +static const struct i2c_device_id max6875_id[] = { + { "max6875", 0 }, + { } +}; +MODULE_DEVICE_TABLE(i2c, max6875_id); + +static struct i2c_driver max6875_driver = { + .driver = { + .name = "max6875", + }, + .probe = max6875_probe, + .remove = max6875_remove, + .id_table = max6875_id, +}; + +module_i2c_driver(max6875_driver); + +MODULE_AUTHOR("Ben Gardner <bgardner@wabtec.com>"); +MODULE_DESCRIPTION("MAX6875 driver"); +MODULE_LICENSE("GPL"); |