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linux/drivers/w1/slaves/w1_ds2438.c
Colin Ian King ee896c5bf2 w1: ds2438: remove redundant initialization of variable crc 
Variable crc is being initialized with a value that is never read,
it is being re-assigned later on. The initialization is redundant
and can be removed.

Cleans up clang scan build warning:
warning: Value stored to 'crc' is never read [deadcode.DeadStores]

Signed-off-by: Colin Ian King <colin.i.king@gmail.com>
Link: https://lore.kernel.org/r/20220522194622.13277-1-colin.i.king@gmail.com
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
2023-05-08 08:14:51 +02:00

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// SPDX-License-Identifier: GPL-2.0-only
/*
* 1-Wire implementation for the ds2438 chip
*
* Copyright (c) 2017 Mariusz Bialonczyk <manio@skyboo.net>
*/
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/device.h>
#include <linux/types.h>
#include <linux/delay.h>
#include <linux/w1.h>
#define W1_FAMILY_DS2438 0x26
#define W1_DS2438_RETRIES 3
/* Memory commands */
#define W1_DS2438_READ_SCRATCH 0xBE
#define W1_DS2438_WRITE_SCRATCH 0x4E
#define W1_DS2438_COPY_SCRATCH 0x48
#define W1_DS2438_RECALL_MEMORY 0xB8
/* Register commands */
#define W1_DS2438_CONVERT_TEMP 0x44
#define W1_DS2438_CONVERT_VOLTAGE 0xB4
#define DS2438_PAGE_SIZE 8
#define DS2438_ADC_INPUT_VAD 0
#define DS2438_ADC_INPUT_VDD 1
#define DS2438_MAX_CONVERSION_TIME 10 /* ms */
/* Page #0 definitions */
#define DS2438_STATUS_REG 0x00 /* Status/Configuration Register */
#define DS2438_STATUS_IAD (1 << 0) /* Current A/D Control Bit */
#define DS2438_STATUS_CA (1 << 1) /* Current Accumulator Configuration */
#define DS2438_STATUS_EE (1 << 2) /* Current Accumulator Shadow Selector bit */
#define DS2438_STATUS_AD (1 << 3) /* Voltage A/D Input Select Bit */
#define DS2438_STATUS_TB (1 << 4) /* Temperature Busy Flag */
#define DS2438_STATUS_NVB (1 << 5) /* Nonvolatile Memory Busy Flag */
#define DS2438_STATUS_ADB (1 << 6) /* A/D Converter Busy Flag */
#define DS2438_TEMP_LSB 0x01
#define DS2438_TEMP_MSB 0x02
#define DS2438_VOLTAGE_LSB 0x03
#define DS2438_VOLTAGE_MSB 0x04
#define DS2438_CURRENT_LSB 0x05
#define DS2438_CURRENT_MSB 0x06
#define DS2438_THRESHOLD 0x07
/* Page #1 definitions */
#define DS2438_ETM_0 0x00
#define DS2438_ETM_1 0x01
#define DS2438_ETM_2 0x02
#define DS2438_ETM_3 0x03
#define DS2438_ICA 0x04
#define DS2438_OFFSET_LSB 0x05
#define DS2438_OFFSET_MSB 0x06
static int w1_ds2438_get_page(struct w1_slave *sl, int pageno, u8 *buf)
{
unsigned int retries = W1_DS2438_RETRIES;
u8 w1_buf[2];
u8 crc;
size_t count;
while (retries--) {
if (w1_reset_select_slave(sl))
continue;
w1_buf[0] = W1_DS2438_RECALL_MEMORY;
w1_buf[1] = (u8)pageno;
w1_write_block(sl->master, w1_buf, 2);
if (w1_reset_select_slave(sl))
continue;
w1_buf[0] = W1_DS2438_READ_SCRATCH;
w1_buf[1] = (u8)pageno;
w1_write_block(sl->master, w1_buf, 2);
count = w1_read_block(sl->master, buf, DS2438_PAGE_SIZE + 1);
if (count == DS2438_PAGE_SIZE + 1) {
crc = w1_calc_crc8(buf, DS2438_PAGE_SIZE);
/* check for correct CRC */
if ((u8)buf[DS2438_PAGE_SIZE] == crc)
return 0;
}
}
return -1;
}
static int w1_ds2438_get_temperature(struct w1_slave *sl, int16_t *temperature)
{
unsigned int retries = W1_DS2438_RETRIES;
u8 w1_buf[DS2438_PAGE_SIZE + 1 /*for CRC*/];
unsigned int tm = DS2438_MAX_CONVERSION_TIME;
unsigned long sleep_rem;
int ret;
mutex_lock(&sl->master->bus_mutex);
while (retries--) {
if (w1_reset_select_slave(sl))
continue;
w1_write_8(sl->master, W1_DS2438_CONVERT_TEMP);
mutex_unlock(&sl->master->bus_mutex);
sleep_rem = msleep_interruptible(tm);
if (sleep_rem != 0) {
ret = -1;
goto post_unlock;
}
if (mutex_lock_interruptible(&sl->master->bus_mutex) != 0) {
ret = -1;
goto post_unlock;
}
break;
}
if (w1_ds2438_get_page(sl, 0, w1_buf) == 0) {
*temperature = (((int16_t) w1_buf[DS2438_TEMP_MSB]) << 8) | ((uint16_t) w1_buf[DS2438_TEMP_LSB]);
ret = 0;
} else
ret = -1;
mutex_unlock(&sl->master->bus_mutex);
post_unlock:
return ret;
}
static int w1_ds2438_change_config_bit(struct w1_slave *sl, u8 mask, u8 value)
{
unsigned int retries = W1_DS2438_RETRIES;
u8 w1_buf[3];
u8 status;
int perform_write = 0;
while (retries--) {
if (w1_reset_select_slave(sl))
continue;
w1_buf[0] = W1_DS2438_RECALL_MEMORY;
w1_buf[1] = 0x00;
w1_write_block(sl->master, w1_buf, 2);
if (w1_reset_select_slave(sl))
continue;
w1_buf[0] = W1_DS2438_READ_SCRATCH;
w1_buf[1] = 0x00;
w1_write_block(sl->master, w1_buf, 2);
/* reading one byte of result */
status = w1_read_8(sl->master);
/* if bit0=1, set a value to a mask for easy compare */
if (value)
value = mask;
if ((status & mask) == value)
return 0; /* already set as requested */
/* changing bit */
status ^= mask;
perform_write = 1;
break;
}
if (perform_write) {
retries = W1_DS2438_RETRIES;
while (retries--) {
if (w1_reset_select_slave(sl))
continue;
w1_buf[0] = W1_DS2438_WRITE_SCRATCH;
w1_buf[1] = 0x00;
w1_buf[2] = status;
w1_write_block(sl->master, w1_buf, 3);
if (w1_reset_select_slave(sl))
continue;
w1_buf[0] = W1_DS2438_COPY_SCRATCH;
w1_buf[1] = 0x00;
w1_write_block(sl->master, w1_buf, 2);
return 0;
}
}
return -1;
}
static int w1_ds2438_change_offset_register(struct w1_slave *sl, u8 *value)
{
unsigned int retries = W1_DS2438_RETRIES;
u8 w1_buf[9];
u8 w1_page1_buf[DS2438_PAGE_SIZE + 1 /*for CRC*/];
if (w1_ds2438_get_page(sl, 1, w1_page1_buf) == 0) {
memcpy(&w1_buf[2], w1_page1_buf, DS2438_PAGE_SIZE - 1); /* last register reserved */
w1_buf[7] = value[0]; /* change only offset register */
w1_buf[8] = value[1];
while (retries--) {
if (w1_reset_select_slave(sl))
continue;
w1_buf[0] = W1_DS2438_WRITE_SCRATCH;
w1_buf[1] = 0x01; /* write to page 1 */
w1_write_block(sl->master, w1_buf, 9);
if (w1_reset_select_slave(sl))
continue;
w1_buf[0] = W1_DS2438_COPY_SCRATCH;
w1_buf[1] = 0x01;
w1_write_block(sl->master, w1_buf, 2);
return 0;
}
}
return -1;
}
static int w1_ds2438_get_voltage(struct w1_slave *sl,
int adc_input, uint16_t *voltage)
{
unsigned int retries = W1_DS2438_RETRIES;
u8 w1_buf[DS2438_PAGE_SIZE + 1 /*for CRC*/];
unsigned int tm = DS2438_MAX_CONVERSION_TIME;
unsigned long sleep_rem;
int ret;
mutex_lock(&sl->master->bus_mutex);
if (w1_ds2438_change_config_bit(sl, DS2438_STATUS_AD, adc_input)) {
ret = -1;
goto pre_unlock;
}
while (retries--) {
if (w1_reset_select_slave(sl))
continue;
w1_write_8(sl->master, W1_DS2438_CONVERT_VOLTAGE);
mutex_unlock(&sl->master->bus_mutex);
sleep_rem = msleep_interruptible(tm);
if (sleep_rem != 0) {
ret = -1;
goto post_unlock;
}
if (mutex_lock_interruptible(&sl->master->bus_mutex) != 0) {
ret = -1;
goto post_unlock;
}
break;
}
if (w1_ds2438_get_page(sl, 0, w1_buf) == 0) {
*voltage = (((uint16_t) w1_buf[DS2438_VOLTAGE_MSB]) << 8) | ((uint16_t) w1_buf[DS2438_VOLTAGE_LSB]);
ret = 0;
} else
ret = -1;
pre_unlock:
mutex_unlock(&sl->master->bus_mutex);
post_unlock:
return ret;
}
static int w1_ds2438_get_current(struct w1_slave *sl, int16_t *voltage)
{
u8 w1_buf[DS2438_PAGE_SIZE + 1 /*for CRC*/];
int ret;
mutex_lock(&sl->master->bus_mutex);
if (w1_ds2438_get_page(sl, 0, w1_buf) == 0) {
/* The voltage measured across current sense resistor RSENS. */
*voltage = (((int16_t) w1_buf[DS2438_CURRENT_MSB]) << 8) | ((int16_t) w1_buf[DS2438_CURRENT_LSB]);
ret = 0;
} else
ret = -1;
mutex_unlock(&sl->master->bus_mutex);
return ret;
}
static ssize_t iad_write(struct file *filp, struct kobject *kobj,
struct bin_attribute *bin_attr, char *buf,
loff_t off, size_t count)
{
struct w1_slave *sl = kobj_to_w1_slave(kobj);
int ret;
if (count != 1 || off != 0)
return -EFAULT;
mutex_lock(&sl->master->bus_mutex);
if (w1_ds2438_change_config_bit(sl, DS2438_STATUS_IAD, *buf & 0x01) == 0)
ret = 1;
else
ret = -EIO;
mutex_unlock(&sl->master->bus_mutex);
return ret;
}
static ssize_t iad_read(struct file *filp, struct kobject *kobj,
struct bin_attribute *bin_attr, char *buf,
loff_t off, size_t count)
{
struct w1_slave *sl = kobj_to_w1_slave(kobj);
int ret;
int16_t voltage;
if (off != 0)
return 0;
if (!buf)
return -EINVAL;
if (w1_ds2438_get_current(sl, &voltage) == 0)
ret = snprintf(buf, count, "%i\n", voltage);
else
ret = -EIO;
return ret;
}
static ssize_t page0_read(struct file *filp, struct kobject *kobj,
struct bin_attribute *bin_attr, char *buf,
loff_t off, size_t count)
{
struct w1_slave *sl = kobj_to_w1_slave(kobj);
int ret;
u8 w1_buf[DS2438_PAGE_SIZE + 1 /*for CRC*/];
if (off != 0)
return 0;
if (!buf)
return -EINVAL;
mutex_lock(&sl->master->bus_mutex);
/* Read no more than page0 size */
if (count > DS2438_PAGE_SIZE)
count = DS2438_PAGE_SIZE;
if (w1_ds2438_get_page(sl, 0, w1_buf) == 0) {
memcpy(buf, &w1_buf, count);
ret = count;
} else
ret = -EIO;
mutex_unlock(&sl->master->bus_mutex);
return ret;
}
static ssize_t page1_read(struct file *filp, struct kobject *kobj,
struct bin_attribute *bin_attr, char *buf,
loff_t off, size_t count)
{
struct w1_slave *sl = kobj_to_w1_slave(kobj);
int ret;
u8 w1_buf[DS2438_PAGE_SIZE + 1 /*for CRC*/];
if (off != 0)
return 0;
if (!buf)
return -EINVAL;
mutex_lock(&sl->master->bus_mutex);
/* Read no more than page1 size */
if (count > DS2438_PAGE_SIZE)
count = DS2438_PAGE_SIZE;
if (w1_ds2438_get_page(sl, 1, w1_buf) == 0) {
memcpy(buf, &w1_buf, count);
ret = count;
} else
ret = -EIO;
mutex_unlock(&sl->master->bus_mutex);
return ret;
}
static ssize_t offset_write(struct file *filp, struct kobject *kobj,
struct bin_attribute *bin_attr, char *buf,
loff_t off, size_t count)
{
struct w1_slave *sl = kobj_to_w1_slave(kobj);
int ret;
mutex_lock(&sl->master->bus_mutex);
if (w1_ds2438_change_offset_register(sl, buf) == 0)
ret = count;
else
ret = -EIO;
mutex_unlock(&sl->master->bus_mutex);
return ret;
}
static ssize_t temperature_read(struct file *filp, struct kobject *kobj,
struct bin_attribute *bin_attr, char *buf,
loff_t off, size_t count)
{
struct w1_slave *sl = kobj_to_w1_slave(kobj);
int ret;
int16_t temp;
if (off != 0)
return 0;
if (!buf)
return -EINVAL;
if (w1_ds2438_get_temperature(sl, &temp) == 0)
ret = snprintf(buf, count, "%i\n", temp);
else
ret = -EIO;
return ret;
}
static ssize_t vad_read(struct file *filp, struct kobject *kobj,
struct bin_attribute *bin_attr, char *buf,
loff_t off, size_t count)
{
struct w1_slave *sl = kobj_to_w1_slave(kobj);
int ret;
uint16_t voltage;
if (off != 0)
return 0;
if (!buf)
return -EINVAL;
if (w1_ds2438_get_voltage(sl, DS2438_ADC_INPUT_VAD, &voltage) == 0)
ret = snprintf(buf, count, "%u\n", voltage);
else
ret = -EIO;
return ret;
}
static ssize_t vdd_read(struct file *filp, struct kobject *kobj,
struct bin_attribute *bin_attr, char *buf,
loff_t off, size_t count)
{
struct w1_slave *sl = kobj_to_w1_slave(kobj);
int ret;
uint16_t voltage;
if (off != 0)
return 0;
if (!buf)
return -EINVAL;
if (w1_ds2438_get_voltage(sl, DS2438_ADC_INPUT_VDD, &voltage) == 0)
ret = snprintf(buf, count, "%u\n", voltage);
else
ret = -EIO;
return ret;
}
static BIN_ATTR_RW(iad, 0);
static BIN_ATTR_RO(page0, DS2438_PAGE_SIZE);
static BIN_ATTR_RO(page1, DS2438_PAGE_SIZE);
static BIN_ATTR_WO(offset, 2);
static BIN_ATTR_RO(temperature, 0/* real length varies */);
static BIN_ATTR_RO(vad, 0/* real length varies */);
static BIN_ATTR_RO(vdd, 0/* real length varies */);
static struct bin_attribute *w1_ds2438_bin_attrs[] = {
&bin_attr_iad,
&bin_attr_page0,
&bin_attr_page1,
&bin_attr_offset,
&bin_attr_temperature,
&bin_attr_vad,
&bin_attr_vdd,
NULL,
};
static const struct attribute_group w1_ds2438_group = {
.bin_attrs = w1_ds2438_bin_attrs,
};
static const struct attribute_group *w1_ds2438_groups[] = {
&w1_ds2438_group,
NULL,
};
static const struct w1_family_ops w1_ds2438_fops = {
.groups = w1_ds2438_groups,
};
static struct w1_family w1_ds2438_family = {
.fid = W1_FAMILY_DS2438,
.fops = &w1_ds2438_fops,
};
module_w1_family(w1_ds2438_family);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Mariusz Bialonczyk <manio@skyboo.net>");
MODULE_DESCRIPTION("1-wire driver for Maxim/Dallas DS2438 Smart Battery Monitor");
MODULE_ALIAS("w1-family-" __stringify(W1_FAMILY_DS2438));
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