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linux/drivers/iio/temperature/max31856.c
Colin Ian King 8e4fefec01 iio: temperature: max31856: fix uninitialized error return 
Currently if mask is neither CHAN_INFO_RAW or CHAN_INFO_SCALE then
then an uninitialized error return 'ret' is returned. Fix this by
adding a default case that ensures -EINVAL is returned for this
specific case.

Addresses-Coverity: ("Uninitialized scalar variable")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
2019-04-14 13:50:09 +01:00

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// SPDX-License-Identifier: GPL-2.0
/* max31856.c
*
* Maxim MAX31856 thermocouple sensor driver
*
* Copyright (C) 2018-2019 Rockwell Collins
*/
#include <linux/module.h>
#include <linux/init.h>
#include <linux/err.h>
#include <linux/spi/spi.h>
#include <linux/iio/iio.h>
#include <linux/iio/sysfs.h>
#include <dt-bindings/iio/temperature/thermocouple.h>
/*
* The MSB of the register value determines whether the following byte will
* be written or read. If it is 0, one or more byte reads will follow.
*/
#define MAX31856_RD_WR_BIT BIT(7)
#define MAX31856_CR0_AUTOCONVERT BIT(7)
#define MAX31856_CR0_1SHOT BIT(6)
#define MAX31856_CR0_OCFAULT BIT(4)
#define MAX31856_CR0_OCFAULT_MASK GENMASK(5, 4)
#define MAX31856_TC_TYPE_MASK GENMASK(3, 0)
#define MAX31856_FAULT_OVUV BIT(1)
#define MAX31856_FAULT_OPEN BIT(0)
/* The MAX31856 registers */
#define MAX31856_CR0_REG 0x00
#define MAX31856_CR1_REG 0x01
#define MAX31856_MASK_REG 0x02
#define MAX31856_CJHF_REG 0x03
#define MAX31856_CJLF_REG 0x04
#define MAX31856_LTHFTH_REG 0x05
#define MAX31856_LTHFTL_REG 0x06
#define MAX31856_LTLFTH_REG 0x07
#define MAX31856_LTLFTL_REG 0x08
#define MAX31856_CJTO_REG 0x09
#define MAX31856_CJTH_REG 0x0A
#define MAX31856_CJTL_REG 0x0B
#define MAX31856_LTCBH_REG 0x0C
#define MAX31856_LTCBM_REG 0x0D
#define MAX31856_LTCBL_REG 0x0E
#define MAX31856_SR_REG 0x0F
static const struct iio_chan_spec max31856_channels[] = {
{ /* Thermocouple Temperature */
.type = IIO_TEMP,
.info_mask_separate =
BIT(IIO_CHAN_INFO_RAW) | BIT(IIO_CHAN_INFO_SCALE),
},
{ /* Cold Junction Temperature */
.type = IIO_TEMP,
.channel2 = IIO_MOD_TEMP_AMBIENT,
.modified = 1,
.info_mask_separate =
BIT(IIO_CHAN_INFO_RAW) | BIT(IIO_CHAN_INFO_SCALE),
},
};
struct max31856_data {
struct spi_device *spi;
u32 thermocouple_type;
};
static int max31856_read(struct max31856_data *data, u8 reg,
u8 val[], unsigned int read_size)
{
return spi_write_then_read(data->spi, &reg, 1, val, read_size);
}
static int max31856_write(struct max31856_data *data, u8 reg,
unsigned int val)
{
u8 buf[2];
buf[0] = reg | (MAX31856_RD_WR_BIT);
buf[1] = val;
return spi_write(data->spi, buf, 2);
}
static int max31856_init(struct max31856_data *data)
{
int ret;
u8 reg_cr0_val, reg_cr1_val;
/* Start by changing to Off mode before making changes as
* some settings are recommended to be set only when the device
* is off
*/
ret = max31856_read(data, MAX31856_CR0_REG, &reg_cr0_val, 1);
if (ret)
return ret;
reg_cr0_val &= ~MAX31856_CR0_AUTOCONVERT;
ret = max31856_write(data, MAX31856_CR0_REG, reg_cr0_val);
if (ret)
return ret;
/* Set thermocouple type based on dts property */
ret = max31856_read(data, MAX31856_CR1_REG, &reg_cr1_val, 1);
if (ret)
return ret;
reg_cr1_val &= ~MAX31856_TC_TYPE_MASK;
reg_cr1_val |= data->thermocouple_type;
ret = max31856_write(data, MAX31856_CR1_REG, reg_cr1_val);
if (ret)
return ret;
/*
* Enable Open circuit fault detection
* Read datasheet for more information: Table 4.
* Value 01 means : Enabled (Once every 16 conversions)
*/
reg_cr0_val &= ~MAX31856_CR0_OCFAULT_MASK;
reg_cr0_val |= MAX31856_CR0_OCFAULT;
/* Set Auto Conversion Mode */
reg_cr0_val &= ~MAX31856_CR0_1SHOT;
reg_cr0_val |= MAX31856_CR0_AUTOCONVERT;
return max31856_write(data, MAX31856_CR0_REG, reg_cr0_val);
}
static int max31856_thermocouple_read(struct max31856_data *data,
struct iio_chan_spec const *chan,
int *val)
{
int ret, offset_cjto;
u8 reg_val[3];
switch (chan->channel2) {
case IIO_NO_MOD:
/*
* Multibyte Read
* MAX31856_LTCBH_REG, MAX31856_LTCBM_REG, MAX31856_LTCBL_REG
*/
ret = max31856_read(data, MAX31856_LTCBH_REG, reg_val, 3);
if (ret)
return ret;
/* Skip last 5 dead bits of LTCBL */
*val = (reg_val[0] << 16 | reg_val[1] << 8 | reg_val[2]) >> 5;
/* Check 7th bit of LTCBH reg. value for sign*/
if (reg_val[0] & 0x80)
*val -= 0x80000;
break;
case IIO_MOD_TEMP_AMBIENT:
/*
* Multibyte Read
* MAX31856_CJTO_REG, MAX31856_CJTH_REG, MAX31856_CJTL_REG
*/
ret = max31856_read(data, MAX31856_CJTO_REG, reg_val, 3);
if (ret)
return ret;
/* Get Cold Junction Temp. offset register value */
offset_cjto = reg_val[0];
/* Get CJTH and CJTL value and skip last 2 dead bits of CJTL */
*val = (reg_val[1] << 8 | reg_val[2]) >> 2;
/* As per datasheet add offset into CJTH and CJTL */
*val += offset_cjto;
/* Check 7th bit of CJTH reg. value for sign */
if (reg_val[1] & 0x80)
*val -= 0x4000;
break;
default:
return -EINVAL;
}
ret = max31856_read(data, MAX31856_SR_REG, reg_val, 1);
if (ret)
return ret;
/* Check for over/under voltage or open circuit fault */
if (reg_val[0] & (MAX31856_FAULT_OVUV | MAX31856_FAULT_OPEN))
return -EIO;
return ret;
}
static int max31856_read_raw(struct iio_dev *indio_dev,
struct iio_chan_spec const *chan,
int *val, int *val2, long mask)
{
struct max31856_data *data = iio_priv(indio_dev);
int ret;
switch (mask) {
case IIO_CHAN_INFO_RAW:
ret = max31856_thermocouple_read(data, chan, val);
if (ret)
return ret;
return IIO_VAL_INT;
case IIO_CHAN_INFO_SCALE:
switch (chan->channel2) {
case IIO_MOD_TEMP_AMBIENT:
/* Cold junction Temp. Data resolution is 0.015625 */
*val = 15;
*val2 = 625000; /* 1000 * 0.015625 */
ret = IIO_VAL_INT_PLUS_MICRO;
break;
default:
/* Thermocouple Temp. Data resolution is 0.0078125 */
*val = 7;
*val2 = 812500; /* 1000 * 0.0078125) */
return IIO_VAL_INT_PLUS_MICRO;
}
break;
default:
ret = -EINVAL;
break;
}
return ret;
}
static ssize_t show_fault(struct device *dev, u8 faultbit, char *buf)
{
struct iio_dev *indio_dev = dev_to_iio_dev(dev);
struct max31856_data *data = iio_priv(indio_dev);
u8 reg_val;
int ret;
bool fault;
ret = max31856_read(data, MAX31856_SR_REG, &reg_val, 1);
if (ret)
return ret;
fault = reg_val & faultbit;
return sprintf(buf, "%d\n", fault);
}
static ssize_t show_fault_ovuv(struct device *dev,
struct device_attribute *attr,
char *buf)
{
return show_fault(dev, MAX31856_FAULT_OVUV, buf);
}
static ssize_t show_fault_oc(struct device *dev,
struct device_attribute *attr,
char *buf)
{
return show_fault(dev, MAX31856_FAULT_OPEN, buf);
}
static IIO_DEVICE_ATTR(fault_ovuv, 0444, show_fault_ovuv, NULL, 0);
static IIO_DEVICE_ATTR(fault_oc, 0444, show_fault_oc, NULL, 0);
static struct attribute *max31856_attributes[] = {
&iio_dev_attr_fault_ovuv.dev_attr.attr,
&iio_dev_attr_fault_oc.dev_attr.attr,
NULL,
};
static const struct attribute_group max31856_group = {
.attrs = max31856_attributes,
};
static const struct iio_info max31856_info = {
.read_raw = max31856_read_raw,
.attrs = &max31856_group,
};
static int max31856_probe(struct spi_device *spi)
{
const struct spi_device_id *id = spi_get_device_id(spi);
struct iio_dev *indio_dev;
struct max31856_data *data;
int ret;
indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*data));
if (!indio_dev)
return -ENOMEM;
data = iio_priv(indio_dev);
data->spi = spi;
spi_set_drvdata(spi, indio_dev);
indio_dev->info = &max31856_info;
indio_dev->name = id->name;
indio_dev->modes = INDIO_DIRECT_MODE;
indio_dev->channels = max31856_channels;
indio_dev->num_channels = ARRAY_SIZE(max31856_channels);
ret = of_property_read_u32(spi->dev.of_node, "thermocouple-type",
&data->thermocouple_type);
if (ret) {
dev_info(&spi->dev,
"Could not read thermocouple type DT property, configuring as a K-Type\n");
data->thermocouple_type = THERMOCOUPLE_TYPE_K;
}
/*
* no need to translate values as the supported types
* have the same value as the #defines
*/
switch (data->thermocouple_type) {
case THERMOCOUPLE_TYPE_B:
case THERMOCOUPLE_TYPE_E:
case THERMOCOUPLE_TYPE_J:
case THERMOCOUPLE_TYPE_K:
case THERMOCOUPLE_TYPE_N:
case THERMOCOUPLE_TYPE_R:
case THERMOCOUPLE_TYPE_S:
case THERMOCOUPLE_TYPE_T:
break;
default:
dev_err(&spi->dev,
"error: thermocouple-type %u not supported by max31856\n"
, data->thermocouple_type);
return -EINVAL;
}
ret = max31856_init(data);
if (ret) {
dev_err(&spi->dev, "error: Failed to configure max31856\n");
return ret;
}
return devm_iio_device_register(&spi->dev, indio_dev);
}
static const struct spi_device_id max31856_id[] = {
{ "max31856", 0 },
{ }
};
MODULE_DEVICE_TABLE(spi, max31856_id);
static const struct of_device_id max31856_of_match[] = {
{ .compatible = "maxim,max31856" },
{ }
};
MODULE_DEVICE_TABLE(of, max31856_of_match);
static struct spi_driver max31856_driver = {
.driver = {
.name = "max31856",
.of_match_table = max31856_of_match,
},
.probe = max31856_probe,
.id_table = max31856_id,
};
module_spi_driver(max31856_driver);
MODULE_AUTHOR("Paresh Chaudhary <paresh.chaudhary@rockwellcollins.com>");
MODULE_AUTHOR("Patrick Havelange <patrick.havelange@essensium.com>");
MODULE_DESCRIPTION("Maxim MAX31856 thermocouple sensor driver");
MODULE_LICENSE("GPL");
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