hwmon: (lm73} Detect and report i2c bus errors (0602934f) · Commits · 戴 / test

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>

drivers/hwmon/lm73.c

+11 −5

Original line number	Diff line number	Diff line
		@@ -49,6 +49,7 @@ static ssize_t set_temp(struct device dev, struct device_attribute da,
		struct i2c_client *client = to_i2c_client(dev);
		long temp;
		short value;
		s32 err;

		int status = kstrtol(buf, 10, &temp);
		if (status < 0)
		@@ -57,8 +58,8 @@ static ssize_t set_temp(struct device dev, struct device_attribute da,
		/* Write value */
		value = (short) SENSORS_LIMIT(temp/250, (LM73_TEMP_MIN*4),
		(LM73_TEMP_MAX*4)) << 5;
		i2c_smbus_write_word_swapped(client, attr->index, value);
		return count;
		err = i2c_smbus_write_word_swapped(client, attr->index, value);
		return (err < 0) ? err : count;
		}

		static ssize_t show_temp(struct device dev, struct device_attribute da,
		@@ -66,11 +67,16 @@ static ssize_t show_temp(struct device dev, struct device_attribute da,
		{
		struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
		struct i2c_client *client = to_i2c_client(dev);
		int temp;

		s32 err = i2c_smbus_read_word_swapped(client, attr->index);
		if (err < 0)
		return err;

		/* use integer division instead of equivalent right shift to
		guarantee arithmetic shift and preserve the sign */
		int temp = ((s16) (i2c_smbus_read_word_swapped(client,
		attr->index))*250) / 32;
		return sprintf(buf, "%d\n", temp);
		temp = (((s16) err) * 250) / 32;
		return scnprintf(buf, PAGE_SIZE, "%d\n", temp);
		}

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