353 lines
7.5 KiB
C
353 lines
7.5 KiB
C
// SPDX-License-Identifier: GPL-2.0+
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/*
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* Hardware monitoring driver for MAX127.
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*
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* Copyright (c) 2020 Facebook Inc.
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*/
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#include <linux/err.h>
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#include <linux/hwmon.h>
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#include <linux/i2c.h>
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#include <linux/init.h>
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#include <linux/module.h>
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/*
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* MAX127 Control Byte. Refer to MAX127 datasheet, Table 1 "Control-Byte
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* Format" for details.
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*/
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#define MAX127_CTRL_START BIT(7)
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#define MAX127_CTRL_SEL_SHIFT 4
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#define MAX127_CTRL_RNG BIT(3)
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#define MAX127_CTRL_BIP BIT(2)
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#define MAX127_CTRL_PD1 BIT(1)
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#define MAX127_CTRL_PD0 BIT(0)
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#define MAX127_NUM_CHANNELS 8
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#define MAX127_SET_CHANNEL(ch) (((ch) & 7) << MAX127_CTRL_SEL_SHIFT)
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/*
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* MAX127 channel input ranges. Refer to MAX127 datasheet, Table 3 "Range
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* and Polarity Selection" for details.
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*/
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#define MAX127_FULL_RANGE 10000 /* 10V */
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#define MAX127_HALF_RANGE 5000 /* 5V */
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/*
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* MAX127 returns 2 bytes at read:
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* - the first byte contains data[11:4].
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* - the second byte contains data[3:0] (MSB) and 4 dummy 0s (LSB).
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* Refer to MAX127 datasheet, "Read a Conversion (Read Cycle)" section
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* for details.
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*/
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#define MAX127_DATA_LEN 2
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#define MAX127_DATA_SHIFT 4
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#define MAX127_SIGN_BIT BIT(11)
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struct max127_data {
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struct mutex lock;
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struct i2c_client *client;
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u8 ctrl_byte[MAX127_NUM_CHANNELS];
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};
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static int max127_select_channel(struct i2c_client *client, u8 ctrl_byte)
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{
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int status;
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struct i2c_msg msg = {
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.addr = client->addr,
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.flags = 0,
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.len = sizeof(ctrl_byte),
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.buf = &ctrl_byte,
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};
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status = i2c_transfer(client->adapter, &msg, 1);
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if (status < 0)
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return status;
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if (status != 1)
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return -EIO;
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return 0;
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}
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static int max127_read_channel(struct i2c_client *client, long *val)
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{
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int status;
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u8 i2c_data[MAX127_DATA_LEN];
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struct i2c_msg msg = {
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.addr = client->addr,
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.flags = I2C_M_RD,
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.len = sizeof(i2c_data),
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.buf = i2c_data,
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};
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status = i2c_transfer(client->adapter, &msg, 1);
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if (status < 0)
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return status;
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if (status != 1)
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return -EIO;
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*val = (i2c_data[1] >> MAX127_DATA_SHIFT) |
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((u16)i2c_data[0] << MAX127_DATA_SHIFT);
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return 0;
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}
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static long max127_process_raw(u8 ctrl_byte, long raw)
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{
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long scale, weight;
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/*
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* MAX127's data coding is binary in unipolar mode with 1 LSB =
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* (Full-Scale/4096) and two’s complement binary in bipolar mode
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* with 1 LSB = [(2 x |FS|)/4096].
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* Refer to MAX127 datasheet, "Transfer Function" section for
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* details.
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*/
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scale = (ctrl_byte & MAX127_CTRL_RNG) ? MAX127_FULL_RANGE :
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MAX127_HALF_RANGE;
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if (ctrl_byte & MAX127_CTRL_BIP) {
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weight = (raw & MAX127_SIGN_BIT);
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raw &= ~MAX127_SIGN_BIT;
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raw -= weight;
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raw *= 2;
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}
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return raw * scale / 4096;
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}
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static int max127_read_input(struct max127_data *data, int channel, long *val)
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{
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long raw;
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int status;
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struct i2c_client *client = data->client;
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u8 ctrl_byte = data->ctrl_byte[channel];
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mutex_lock(&data->lock);
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status = max127_select_channel(client, ctrl_byte);
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if (status)
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goto exit;
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status = max127_read_channel(client, &raw);
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if (status)
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goto exit;
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*val = max127_process_raw(ctrl_byte, raw);
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exit:
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mutex_unlock(&data->lock);
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return status;
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}
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static int max127_read_min(struct max127_data *data, int channel, long *val)
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{
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u8 rng_bip = (data->ctrl_byte[channel] >> 2) & 3;
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static const int min_input_map[4] = {
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0, /* RNG=0, BIP=0 */
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-MAX127_HALF_RANGE, /* RNG=0, BIP=1 */
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0, /* RNG=1, BIP=0 */
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-MAX127_FULL_RANGE, /* RNG=1, BIP=1 */
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};
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*val = min_input_map[rng_bip];
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return 0;
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}
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static int max127_read_max(struct max127_data *data, int channel, long *val)
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{
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u8 rng_bip = (data->ctrl_byte[channel] >> 2) & 3;
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static const int max_input_map[4] = {
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MAX127_HALF_RANGE, /* RNG=0, BIP=0 */
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MAX127_HALF_RANGE, /* RNG=0, BIP=1 */
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MAX127_FULL_RANGE, /* RNG=1, BIP=0 */
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MAX127_FULL_RANGE, /* RNG=1, BIP=1 */
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};
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*val = max_input_map[rng_bip];
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return 0;
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}
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static int max127_write_min(struct max127_data *data, int channel, long val)
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{
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u8 ctrl;
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mutex_lock(&data->lock);
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ctrl = data->ctrl_byte[channel];
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if (val <= -MAX127_FULL_RANGE) {
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ctrl |= (MAX127_CTRL_RNG | MAX127_CTRL_BIP);
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} else if (val < 0) {
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ctrl |= MAX127_CTRL_BIP;
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ctrl &= ~MAX127_CTRL_RNG;
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} else {
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ctrl &= ~MAX127_CTRL_BIP;
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}
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data->ctrl_byte[channel] = ctrl;
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mutex_unlock(&data->lock);
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return 0;
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}
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static int max127_write_max(struct max127_data *data, int channel, long val)
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{
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mutex_lock(&data->lock);
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if (val >= MAX127_FULL_RANGE)
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data->ctrl_byte[channel] |= MAX127_CTRL_RNG;
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else
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data->ctrl_byte[channel] &= ~MAX127_CTRL_RNG;
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mutex_unlock(&data->lock);
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return 0;
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}
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static umode_t max127_is_visible(const void *_data,
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enum hwmon_sensor_types type,
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u32 attr, int channel)
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{
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if (type == hwmon_in) {
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switch (attr) {
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case hwmon_in_input:
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return 0444;
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case hwmon_in_min:
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case hwmon_in_max:
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return 0644;
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default:
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break;
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}
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}
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return 0;
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}
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static int max127_read(struct device *dev, enum hwmon_sensor_types type,
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u32 attr, int channel, long *val)
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{
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int status;
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struct max127_data *data = dev_get_drvdata(dev);
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if (type != hwmon_in)
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return -EOPNOTSUPP;
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switch (attr) {
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case hwmon_in_input:
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status = max127_read_input(data, channel, val);
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break;
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case hwmon_in_min:
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status = max127_read_min(data, channel, val);
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break;
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case hwmon_in_max:
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status = max127_read_max(data, channel, val);
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break;
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default:
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status = -EOPNOTSUPP;
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break;
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}
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return status;
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}
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static int max127_write(struct device *dev, enum hwmon_sensor_types type,
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u32 attr, int channel, long val)
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{
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int status;
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struct max127_data *data = dev_get_drvdata(dev);
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if (type != hwmon_in)
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return -EOPNOTSUPP;
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switch (attr) {
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case hwmon_in_min:
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status = max127_write_min(data, channel, val);
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break;
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case hwmon_in_max:
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status = max127_write_max(data, channel, val);
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break;
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default:
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status = -EOPNOTSUPP;
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break;
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}
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return status;
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}
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static const struct hwmon_ops max127_hwmon_ops = {
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.is_visible = max127_is_visible,
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.read = max127_read,
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.write = max127_write,
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};
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static const struct hwmon_channel_info *max127_info[] = {
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HWMON_CHANNEL_INFO(in,
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HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
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HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
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HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
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HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
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HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
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HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
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HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
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HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX),
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NULL,
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};
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static const struct hwmon_chip_info max127_chip_info = {
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.ops = &max127_hwmon_ops,
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.info = max127_info,
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};
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static int max127_probe(struct i2c_client *client,
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const struct i2c_device_id *id)
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{
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int i;
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struct device *hwmon_dev;
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struct max127_data *data;
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struct device *dev = &client->dev;
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data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
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if (!data)
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return -ENOMEM;
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data->client = client;
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mutex_init(&data->lock);
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for (i = 0; i < ARRAY_SIZE(data->ctrl_byte); i++)
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data->ctrl_byte[i] = (MAX127_CTRL_START |
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MAX127_SET_CHANNEL(i));
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hwmon_dev = devm_hwmon_device_register_with_info(dev, client->name,
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data,
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&max127_chip_info,
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NULL);
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return PTR_ERR_OR_ZERO(hwmon_dev);
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}
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static const struct i2c_device_id max127_id[] = {
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{ "max127", 0 },
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{ }
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};
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MODULE_DEVICE_TABLE(i2c, max127_id);
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static struct i2c_driver max127_driver = {
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.class = I2C_CLASS_HWMON,
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.driver = {
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.name = "max127",
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},
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.probe = max127_probe,
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.id_table = max127_id,
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};
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module_i2c_driver(max127_driver);
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MODULE_LICENSE("GPL");
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MODULE_AUTHOR("Mike Choi <mikechoi@fb.com>");
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MODULE_AUTHOR("Tao Ren <rentao.bupt@gmail.com>");
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MODULE_DESCRIPTION("MAX127 Hardware Monitoring driver");
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