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![Chris Verges](/assets/img/avatar_default.png)
If an LM73 device does not exist on an I2C bus, attempts to communicate with the device result in an error code returned from the i2c read/write functions. The current lm73 driver casts that return value from a s32 type to a s16 type, then converts it to a temperature in celsius. Because negative temperatures are valid, it is difficult to distinguish between an error code printed to the response buffer and a negative temperature recorded by the sensor. The solution is to evaluate the return value from the i2c functions before performing any temperature calculations. If the i2c function did not succeed, the error code should be passed back through the virtual file system layer instead of being printed into the response buffer. Before: $ cat /sys/class/hwmon/hwmon0/device/temp1_input -46 After: $ cat /sys/class/hwmon/hwmon0/device/temp1_input cat: read error: No such device or address Signed-off-by: Chris Verges <kg4ysn@gmail.com> Cc: stable@vger.kernel.org Signed-off-by: Guenter Roeck <linux@roeck-us.net>
207 lines
5.2 KiB
C
207 lines
5.2 KiB
C
/*
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* LM73 Sensor driver
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* Based on LM75
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*
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* Copyright (C) 2007, CenoSYS (www.cenosys.com).
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* Copyright (C) 2009, Bollore telecom (www.bolloretelecom.eu).
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*
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* Guillaume Ligneul <guillaume.ligneul@gmail.com>
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* Adrien Demarez <adrien.demarez@bolloretelecom.eu>
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* Jeremy Laine <jeremy.laine@bolloretelecom.eu>
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*
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* This software program is licensed subject to the GNU General Public License
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* (GPL).Version 2,June 1991, available at
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* http://www.gnu.org/licenses/old-licenses/gpl-2.0.html
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*/
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#include <linux/module.h>
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#include <linux/init.h>
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#include <linux/i2c.h>
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#include <linux/hwmon.h>
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#include <linux/hwmon-sysfs.h>
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#include <linux/err.h>
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/* Addresses scanned */
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static const unsigned short normal_i2c[] = { 0x48, 0x49, 0x4a, 0x4c,
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0x4d, 0x4e, I2C_CLIENT_END };
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/* LM73 registers */
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#define LM73_REG_INPUT 0x00
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#define LM73_REG_CONF 0x01
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#define LM73_REG_MAX 0x02
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#define LM73_REG_MIN 0x03
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#define LM73_REG_CTRL 0x04
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#define LM73_REG_ID 0x07
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#define LM73_ID 0x9001 /* 0x0190, byte-swapped */
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#define DRVNAME "lm73"
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#define LM73_TEMP_MIN (-40)
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#define LM73_TEMP_MAX 150
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/*-----------------------------------------------------------------------*/
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static ssize_t set_temp(struct device *dev, struct device_attribute *da,
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const char *buf, size_t count)
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{
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struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
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struct i2c_client *client = to_i2c_client(dev);
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long temp;
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short value;
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s32 err;
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int status = kstrtol(buf, 10, &temp);
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if (status < 0)
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return status;
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/* Write value */
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value = (short) SENSORS_LIMIT(temp/250, (LM73_TEMP_MIN*4),
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(LM73_TEMP_MAX*4)) << 5;
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err = i2c_smbus_write_word_swapped(client, attr->index, value);
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return (err < 0) ? err : count;
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}
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static ssize_t show_temp(struct device *dev, struct device_attribute *da,
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char *buf)
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{
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struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
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struct i2c_client *client = to_i2c_client(dev);
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int temp;
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s32 err = i2c_smbus_read_word_swapped(client, attr->index);
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if (err < 0)
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return err;
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/* use integer division instead of equivalent right shift to
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guarantee arithmetic shift and preserve the sign */
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temp = (((s16) err) * 250) / 32;
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return scnprintf(buf, PAGE_SIZE, "%d\n", temp);
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}
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/*-----------------------------------------------------------------------*/
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/* sysfs attributes for hwmon */
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static SENSOR_DEVICE_ATTR(temp1_max, S_IWUSR | S_IRUGO,
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show_temp, set_temp, LM73_REG_MAX);
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static SENSOR_DEVICE_ATTR(temp1_min, S_IWUSR | S_IRUGO,
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show_temp, set_temp, LM73_REG_MIN);
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static SENSOR_DEVICE_ATTR(temp1_input, S_IRUGO,
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show_temp, NULL, LM73_REG_INPUT);
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static struct attribute *lm73_attributes[] = {
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&sensor_dev_attr_temp1_input.dev_attr.attr,
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&sensor_dev_attr_temp1_max.dev_attr.attr,
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&sensor_dev_attr_temp1_min.dev_attr.attr,
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NULL
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};
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static const struct attribute_group lm73_group = {
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.attrs = lm73_attributes,
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};
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/*-----------------------------------------------------------------------*/
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/* device probe and removal */
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static int
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lm73_probe(struct i2c_client *client, const struct i2c_device_id *id)
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{
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struct device *hwmon_dev;
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int status;
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/* Register sysfs hooks */
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status = sysfs_create_group(&client->dev.kobj, &lm73_group);
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if (status)
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return status;
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hwmon_dev = hwmon_device_register(&client->dev);
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if (IS_ERR(hwmon_dev)) {
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status = PTR_ERR(hwmon_dev);
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goto exit_remove;
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}
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i2c_set_clientdata(client, hwmon_dev);
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dev_info(&client->dev, "%s: sensor '%s'\n",
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dev_name(hwmon_dev), client->name);
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return 0;
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exit_remove:
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sysfs_remove_group(&client->dev.kobj, &lm73_group);
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return status;
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}
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static int lm73_remove(struct i2c_client *client)
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{
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struct device *hwmon_dev = i2c_get_clientdata(client);
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hwmon_device_unregister(hwmon_dev);
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sysfs_remove_group(&client->dev.kobj, &lm73_group);
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return 0;
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}
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static const struct i2c_device_id lm73_ids[] = {
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{ "lm73", 0 },
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{ /* LIST END */ }
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};
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MODULE_DEVICE_TABLE(i2c, lm73_ids);
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/* Return 0 if detection is successful, -ENODEV otherwise */
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static int lm73_detect(struct i2c_client *new_client,
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struct i2c_board_info *info)
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{
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struct i2c_adapter *adapter = new_client->adapter;
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int id, ctrl, conf;
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if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE_DATA |
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I2C_FUNC_SMBUS_WORD_DATA))
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return -ENODEV;
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/*
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* Do as much detection as possible with byte reads first, as word
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* reads can confuse other devices.
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*/
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ctrl = i2c_smbus_read_byte_data(new_client, LM73_REG_CTRL);
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if (ctrl < 0 || (ctrl & 0x10))
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return -ENODEV;
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conf = i2c_smbus_read_byte_data(new_client, LM73_REG_CONF);
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if (conf < 0 || (conf & 0x0c))
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return -ENODEV;
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id = i2c_smbus_read_byte_data(new_client, LM73_REG_ID);
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if (id < 0 || id != (LM73_ID & 0xff))
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return -ENODEV;
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/* Check device ID */
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id = i2c_smbus_read_word_data(new_client, LM73_REG_ID);
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if (id < 0 || id != LM73_ID)
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return -ENODEV;
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strlcpy(info->type, "lm73", I2C_NAME_SIZE);
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return 0;
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}
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static struct i2c_driver lm73_driver = {
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.class = I2C_CLASS_HWMON,
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.driver = {
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.name = "lm73",
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},
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.probe = lm73_probe,
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.remove = lm73_remove,
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.id_table = lm73_ids,
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.detect = lm73_detect,
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.address_list = normal_i2c,
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};
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module_i2c_driver(lm73_driver);
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MODULE_AUTHOR("Guillaume Ligneul <guillaume.ligneul@gmail.com>");
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MODULE_DESCRIPTION("LM73 driver");
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MODULE_LICENSE("GPL");
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