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![Rasmus Villemoes](/assets/img/avatar_default.png)
The comment above (data << 2) >> 2 explains what the intention is: To use bit 13 of the 14-bit value data as the sign bit. However, this doesn't work due to C's promotion rules. data has type s16, but data << 2 has type int. To get sign extension, that expression would have to be cast back to an s16 before being shifted (at which point C's promotion rules would then kick in again and promote the left operand to int). As it stands, both expressions are no-ops for any value of data. Avoid these subtleties by using the existing API for this. sign_extend32 works equally well for 8 and 16 bit types. Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk> Signed-off-by: Guenter Roeck <linux@roeck-us.net>
171 lines
3.8 KiB
C
171 lines
3.8 KiB
C
/*
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* AD7314 digital temperature sensor driver for AD7314, ADT7301 and ADT7302
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*
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* Copyright 2010 Analog Devices Inc.
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*
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* Licensed under the GPL-2 or later.
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*
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* Conversion to hwmon from IIO done by Jonathan Cameron <jic23@cam.ac.uk>
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*/
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#include <linux/device.h>
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#include <linux/kernel.h>
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#include <linux/slab.h>
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#include <linux/sysfs.h>
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#include <linux/spi/spi.h>
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#include <linux/module.h>
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#include <linux/err.h>
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#include <linux/hwmon.h>
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#include <linux/hwmon-sysfs.h>
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#include <linux/bitops.h>
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/*
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* AD7314 temperature masks
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*/
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#define AD7314_TEMP_MASK 0x7FE0
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#define AD7314_TEMP_SHIFT 5
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/*
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* ADT7301 and ADT7302 temperature masks
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*/
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#define ADT7301_TEMP_MASK 0x3FFF
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enum ad7314_variant {
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adt7301,
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adt7302,
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ad7314,
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};
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struct ad7314_data {
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struct spi_device *spi_dev;
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struct device *hwmon_dev;
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u16 rx ____cacheline_aligned;
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};
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static int ad7314_spi_read(struct ad7314_data *chip)
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{
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int ret;
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ret = spi_read(chip->spi_dev, (u8 *)&chip->rx, sizeof(chip->rx));
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if (ret < 0) {
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dev_err(&chip->spi_dev->dev, "SPI read error\n");
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return ret;
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}
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return be16_to_cpu(chip->rx);
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}
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static ssize_t ad7314_show_temperature(struct device *dev,
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struct device_attribute *attr,
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char *buf)
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{
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struct ad7314_data *chip = dev_get_drvdata(dev);
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s16 data;
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int ret;
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ret = ad7314_spi_read(chip);
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if (ret < 0)
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return ret;
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switch (spi_get_device_id(chip->spi_dev)->driver_data) {
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case ad7314:
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data = (ret & AD7314_TEMP_MASK) >> AD7314_TEMP_SHIFT;
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data = sign_extend32(data, 9);
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return sprintf(buf, "%d\n", 250 * data);
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case adt7301:
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case adt7302:
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/*
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* Documented as a 13 bit twos complement register
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* with a sign bit - which is a 14 bit 2's complement
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* register. 1lsb - 31.25 milli degrees centigrade
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*/
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data = ret & ADT7301_TEMP_MASK;
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data = sign_extend32(data, 13);
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return sprintf(buf, "%d\n",
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DIV_ROUND_CLOSEST(data * 3125, 100));
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default:
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return -EINVAL;
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}
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}
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static ssize_t ad7314_show_name(struct device *dev,
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struct device_attribute *devattr, char *buf)
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{
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return sprintf(buf, "%s\n", to_spi_device(dev)->modalias);
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}
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static DEVICE_ATTR(name, S_IRUGO, ad7314_show_name, NULL);
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static SENSOR_DEVICE_ATTR(temp1_input, S_IRUGO,
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ad7314_show_temperature, NULL, 0);
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static struct attribute *ad7314_attributes[] = {
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&dev_attr_name.attr,
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&sensor_dev_attr_temp1_input.dev_attr.attr,
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NULL,
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};
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static const struct attribute_group ad7314_group = {
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.attrs = ad7314_attributes,
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};
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static int ad7314_probe(struct spi_device *spi_dev)
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{
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int ret;
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struct ad7314_data *chip;
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chip = devm_kzalloc(&spi_dev->dev, sizeof(*chip), GFP_KERNEL);
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if (chip == NULL)
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return -ENOMEM;
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spi_set_drvdata(spi_dev, chip);
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ret = sysfs_create_group(&spi_dev->dev.kobj, &ad7314_group);
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if (ret < 0)
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return ret;
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chip->hwmon_dev = hwmon_device_register(&spi_dev->dev);
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if (IS_ERR(chip->hwmon_dev)) {
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ret = PTR_ERR(chip->hwmon_dev);
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goto error_remove_group;
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}
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chip->spi_dev = spi_dev;
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return 0;
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error_remove_group:
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sysfs_remove_group(&spi_dev->dev.kobj, &ad7314_group);
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return ret;
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}
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static int ad7314_remove(struct spi_device *spi_dev)
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{
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struct ad7314_data *chip = spi_get_drvdata(spi_dev);
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hwmon_device_unregister(chip->hwmon_dev);
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sysfs_remove_group(&spi_dev->dev.kobj, &ad7314_group);
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return 0;
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}
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static const struct spi_device_id ad7314_id[] = {
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{ "adt7301", adt7301 },
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{ "adt7302", adt7302 },
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{ "ad7314", ad7314 },
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{ }
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};
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MODULE_DEVICE_TABLE(spi, ad7314_id);
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static struct spi_driver ad7314_driver = {
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.driver = {
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.name = "ad7314",
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.owner = THIS_MODULE,
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},
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.probe = ad7314_probe,
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.remove = ad7314_remove,
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.id_table = ad7314_id,
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};
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module_spi_driver(ad7314_driver);
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MODULE_AUTHOR("Sonic Zhang <sonic.zhang@analog.com>");
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MODULE_DESCRIPTION("Analog Devices AD7314, ADT7301 and ADT7302 digital temperature sensor driver");
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MODULE_LICENSE("GPL v2");
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