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207 lines
5.0 KiB
207 lines
5.0 KiB
// SPDX-License-Identifier: GPL-2.0-only |
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/* |
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* max6875.c - driver for MAX6874/MAX6875 |
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* |
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* Copyright (C) 2005 Ben Gardner <[email protected]> |
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* |
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* Based on eeprom.c |
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* |
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* The MAX6875 has a bank of registers and two banks of EEPROM. |
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* Address ranges are defined as follows: |
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* * 0x0000 - 0x0046 = configuration registers |
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* * 0x8000 - 0x8046 = configuration EEPROM |
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* * 0x8100 - 0x82FF = user EEPROM |
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* |
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* This driver makes the user EEPROM available for read. |
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* |
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* The registers & config EEPROM should be accessed via i2c-dev. |
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* |
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* The MAX6875 ignores the lowest address bit, so each chip responds to |
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* two addresses - 0x50/0x51 and 0x52/0x53. |
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* |
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* Note that the MAX6875 uses i2c_smbus_write_byte_data() to set the read |
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* address, so this driver is destructive if loaded for the wrong EEPROM chip. |
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*/ |
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#include <linux/kernel.h> |
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#include <linux/module.h> |
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#include <linux/slab.h> |
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#include <linux/i2c.h> |
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#include <linux/mutex.h> |
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/* The MAX6875 can only read/write 16 bytes at a time */ |
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#define SLICE_SIZE 16 |
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#define SLICE_BITS 4 |
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/* USER EEPROM is at addresses 0x8100 - 0x82FF */ |
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#define USER_EEPROM_BASE 0x8100 |
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#define USER_EEPROM_SIZE 0x0200 |
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#define USER_EEPROM_SLICES 32 |
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/* MAX6875 commands */ |
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#define MAX6875_CMD_BLK_READ 0x84 |
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/* Each client has this additional data */ |
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struct max6875_data { |
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struct i2c_client *fake_client; |
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struct mutex update_lock; |
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u32 valid; |
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u8 data[USER_EEPROM_SIZE]; |
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unsigned long last_updated[USER_EEPROM_SLICES]; |
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}; |
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static void max6875_update_slice(struct i2c_client *client, int slice) |
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{ |
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struct max6875_data *data = i2c_get_clientdata(client); |
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int i, j, addr; |
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u8 *buf; |
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if (slice >= USER_EEPROM_SLICES) |
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return; |
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mutex_lock(&data->update_lock); |
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buf = &data->data[slice << SLICE_BITS]; |
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if (!(data->valid & (1 << slice)) || |
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time_after(jiffies, data->last_updated[slice])) { |
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dev_dbg(&client->dev, "Starting update of slice %u\n", slice); |
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data->valid &= ~(1 << slice); |
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addr = USER_EEPROM_BASE + (slice << SLICE_BITS); |
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/* select the eeprom address */ |
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if (i2c_smbus_write_byte_data(client, addr >> 8, addr & 0xFF)) { |
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dev_err(&client->dev, "address set failed\n"); |
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goto exit_up; |
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} |
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if (i2c_check_functionality(client->adapter, |
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I2C_FUNC_SMBUS_READ_I2C_BLOCK)) { |
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if (i2c_smbus_read_i2c_block_data(client, |
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MAX6875_CMD_BLK_READ, |
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SLICE_SIZE, |
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buf) != SLICE_SIZE) { |
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goto exit_up; |
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} |
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} else { |
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for (i = 0; i < SLICE_SIZE; i++) { |
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j = i2c_smbus_read_byte(client); |
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if (j < 0) { |
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goto exit_up; |
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} |
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buf[i] = j; |
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} |
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} |
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data->last_updated[slice] = jiffies; |
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data->valid |= (1 << slice); |
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} |
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exit_up: |
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mutex_unlock(&data->update_lock); |
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} |
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static ssize_t max6875_read(struct file *filp, struct kobject *kobj, |
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struct bin_attribute *bin_attr, |
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char *buf, loff_t off, size_t count) |
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{ |
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struct i2c_client *client = kobj_to_i2c_client(kobj); |
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struct max6875_data *data = i2c_get_clientdata(client); |
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int slice, max_slice; |
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/* refresh slices which contain requested bytes */ |
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max_slice = (off + count - 1) >> SLICE_BITS; |
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for (slice = (off >> SLICE_BITS); slice <= max_slice; slice++) |
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max6875_update_slice(client, slice); |
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memcpy(buf, &data->data[off], count); |
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return count; |
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} |
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static const struct bin_attribute user_eeprom_attr = { |
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.attr = { |
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.name = "eeprom", |
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.mode = S_IRUGO, |
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}, |
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.size = USER_EEPROM_SIZE, |
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.read = max6875_read, |
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}; |
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static int max6875_probe(struct i2c_client *client, |
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const struct i2c_device_id *id) |
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{ |
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struct i2c_adapter *adapter = client->adapter; |
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struct max6875_data *data; |
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int err; |
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if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_WRITE_BYTE_DATA |
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| I2C_FUNC_SMBUS_READ_BYTE)) |
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return -ENODEV; |
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/* Only bind to even addresses */ |
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if (client->addr & 1) |
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return -ENODEV; |
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data = kzalloc(sizeof(struct max6875_data), GFP_KERNEL); |
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if (!data) |
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return -ENOMEM; |
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/* A fake client is created on the odd address */ |
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data->fake_client = i2c_new_dummy_device(client->adapter, client->addr + 1); |
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if (IS_ERR(data->fake_client)) { |
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err = PTR_ERR(data->fake_client); |
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goto exit_kfree; |
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} |
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/* Init real i2c_client */ |
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i2c_set_clientdata(client, data); |
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mutex_init(&data->update_lock); |
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err = sysfs_create_bin_file(&client->dev.kobj, &user_eeprom_attr); |
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if (err) |
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goto exit_remove_fake; |
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return 0; |
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exit_remove_fake: |
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i2c_unregister_device(data->fake_client); |
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exit_kfree: |
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kfree(data); |
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return err; |
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} |
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static int max6875_remove(struct i2c_client *client) |
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{ |
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struct max6875_data *data = i2c_get_clientdata(client); |
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i2c_unregister_device(data->fake_client); |
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sysfs_remove_bin_file(&client->dev.kobj, &user_eeprom_attr); |
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kfree(data); |
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return 0; |
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} |
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static const struct i2c_device_id max6875_id[] = { |
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{ "max6875", 0 }, |
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{ } |
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}; |
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MODULE_DEVICE_TABLE(i2c, max6875_id); |
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static struct i2c_driver max6875_driver = { |
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.driver = { |
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.name = "max6875", |
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}, |
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.probe = max6875_probe, |
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.remove = max6875_remove, |
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.id_table = max6875_id, |
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}; |
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module_i2c_driver(max6875_driver); |
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MODULE_AUTHOR("Ben Gardner <[email protected]>"); |
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MODULE_DESCRIPTION("MAX6875 driver"); |
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MODULE_LICENSE("GPL");
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