[PATCH v2 2/3] hwmon: (lm87) Propagate cached sensor read errors
From: Baek Kyu, Kim
Date: Thu Oct 29 2026 - 12:44:34 EST
Abort cache refresh when an I2C read fails and pass the error to
sysfs readers instead of returning stale or invalid sensor values.
Read the alarm registers last, since reading them can clear latched
alarms. Preserve the first alarm byte if reading the second fails,
so a retry can still report the captured alarm.
Signed-off-by: Baek Kyu, Kim <pocj8ur4in@xxxxxxxxx>
---
drivers/hwmon/lm87.c | 202 +++++++++++++++++++++++++++++++++----------
1 file changed, 158 insertions(+), 44 deletions(-)
diff --git a/drivers/hwmon/lm87.c b/drivers/hwmon/lm87.c
index c118a7ff718b..a66d486b314c 100644
--- a/drivers/hwmon/lm87.c
+++ b/drivers/hwmon/lm87.c
@@ -170,6 +170,7 @@ struct lm87_data {
u8 aout; /* register value */
u16 alarms; /* register values, combined */
+ u16 pending_alarms; /* alarms read before an I2C error */
u8 vid; /* register values, combined */
u8 vrm;
@@ -186,75 +187,138 @@ static inline int lm87_write_value(struct i2c_client *client, u8 reg, u8 value)
return i2c_smbus_write_byte_data(client, reg, value);
}
+static int lm87_read_reg(struct i2c_client *client, u8 reg, u8 *value)
+{
+ int ret = lm87_read_value(client, reg);
+
+ if (ret < 0)
+ return ret;
+ *value = ret;
+ return 0;
+}
+
+static int lm87_read_temp(struct i2c_client *client, u8 reg, s8 *value)
+{
+ int ret = lm87_read_value(client, reg);
+
+ if (ret < 0)
+ return ret;
+ *value = ret;
+ return 0;
+}
+
static struct lm87_data *lm87_update_device(struct device *dev)
{
struct i2c_client *client = dev_get_drvdata(dev);
struct lm87_data *data = i2c_get_clientdata(client);
+ int i, j, ret;
+ u8 first, second;
mutex_lock(&data->update_lock);
if (time_after(jiffies, data->last_updated + HZ) || !data->valid) {
- int i, j;
-
dev_dbg(&client->dev, "Updating data.\n");
i = (data->channel & CHAN_TEMP3) ? 1 : 0;
j = (data->channel & CHAN_TEMP3) ? 5 : 6;
for (; i < j; i++) {
- data->in[i] = lm87_read_value(client,
- LM87_REG_IN(i));
- data->in_min[i] = lm87_read_value(client,
- LM87_REG_IN_MIN(i));
- data->in_max[i] = lm87_read_value(client,
- LM87_REG_IN_MAX(i));
+ ret = lm87_read_reg(client, LM87_REG_IN(i), &data->in[i]);
+ if (ret < 0)
+ goto error;
+ ret = lm87_read_reg(client, LM87_REG_IN_MIN(i),
+ &data->in_min[i]);
+ if (ret < 0)
+ goto error;
+ ret = lm87_read_reg(client, LM87_REG_IN_MAX(i),
+ &data->in_max[i]);
+ if (ret < 0)
+ goto error;
}
for (i = 0; i < 2; i++) {
if (data->channel & CHAN_NO_FAN(i)) {
- data->in[6+i] = lm87_read_value(client,
- LM87_REG_AIN(i));
- data->in_max[6+i] = lm87_read_value(client,
- LM87_REG_AIN_MAX(i));
- data->in_min[6+i] = lm87_read_value(client,
- LM87_REG_AIN_MIN(i));
-
+ ret = lm87_read_reg(client, LM87_REG_AIN(i),
+ &data->in[6 + i]);
+ if (ret < 0)
+ goto error;
+ ret = lm87_read_reg(client, LM87_REG_AIN_MAX(i),
+ &data->in_max[6 + i]);
+ if (ret < 0)
+ goto error;
+ ret = lm87_read_reg(client, LM87_REG_AIN_MIN(i),
+ &data->in_min[6 + i]);
+ if (ret < 0)
+ goto error;
} else {
- data->fan[i] = lm87_read_value(client,
- LM87_REG_FAN(i));
- data->fan_min[i] = lm87_read_value(client,
- LM87_REG_FAN_MIN(i));
+ ret = lm87_read_reg(client, LM87_REG_FAN(i),
+ &data->fan[i]);
+ if (ret < 0)
+ goto error;
+ ret = lm87_read_reg(client, LM87_REG_FAN_MIN(i),
+ &data->fan_min[i]);
+ if (ret < 0)
+ goto error;
}
}
j = (data->channel & CHAN_TEMP3) ? 3 : 2;
for (i = 0 ; i < j; i++) {
- data->temp[i] = lm87_read_value(client,
- LM87_REG_TEMP[i]);
- data->temp_high[i] = lm87_read_value(client,
- LM87_REG_TEMP_HIGH[i]);
- data->temp_low[i] = lm87_read_value(client,
- LM87_REG_TEMP_LOW[i]);
+ ret = lm87_read_temp(client, LM87_REG_TEMP[i],
+ &data->temp[i]);
+ if (ret < 0)
+ goto error;
+ ret = lm87_read_temp(client, LM87_REG_TEMP_HIGH[i],
+ &data->temp_high[i]);
+ if (ret < 0)
+ goto error;
+ ret = lm87_read_temp(client, LM87_REG_TEMP_LOW[i],
+ &data->temp_low[i]);
+ if (ret < 0)
+ goto error;
}
- i = lm87_read_value(client, LM87_REG_TEMP_HW_INT_LOCK);
- j = lm87_read_value(client, LM87_REG_TEMP_HW_INT);
- data->temp_crit_int = min(i, j);
-
- i = lm87_read_value(client, LM87_REG_TEMP_HW_EXT_LOCK);
- j = lm87_read_value(client, LM87_REG_TEMP_HW_EXT);
- data->temp_crit_ext = min(i, j);
-
- i = lm87_read_value(client, LM87_REG_VID_FAN_DIV);
- data->fan_div[0] = (i >> 4) & 0x03;
- data->fan_div[1] = (i >> 6) & 0x03;
- data->vid = (i & 0x0F)
- | (lm87_read_value(client, LM87_REG_VID4) & 0x01)
- << 4;
-
- data->alarms = lm87_read_value(client, LM87_REG_ALARMS1)
- | (lm87_read_value(client, LM87_REG_ALARMS2)
- << 8);
- data->aout = lm87_read_value(client, LM87_REG_AOUT);
+ ret = lm87_read_reg(client, LM87_REG_TEMP_HW_INT_LOCK,
+ &first);
+ if (ret < 0)
+ goto error;
+ ret = lm87_read_reg(client, LM87_REG_TEMP_HW_INT, &second);
+ if (ret < 0)
+ goto error;
+ data->temp_crit_int = min(first, second);
+
+ ret = lm87_read_reg(client, LM87_REG_TEMP_HW_EXT_LOCK,
+ &first);
+ if (ret < 0)
+ goto error;
+ ret = lm87_read_reg(client, LM87_REG_TEMP_HW_EXT, &second);
+ if (ret < 0)
+ goto error;
+ data->temp_crit_ext = min(first, second);
+
+ ret = lm87_read_reg(client, LM87_REG_VID_FAN_DIV, &first);
+ if (ret < 0)
+ goto error;
+ data->fan_div[0] = (first >> 4) & 0x03;
+ data->fan_div[1] = (first >> 6) & 0x03;
+ ret = lm87_read_reg(client, LM87_REG_VID4, &second);
+ if (ret < 0)
+ goto error;
+ data->vid = (first & 0x0F) | (second & 0x01) << 4;
+
+ ret = lm87_read_reg(client, LM87_REG_AOUT, &data->aout);
+ if (ret < 0)
+ goto error;
+
+ ret = lm87_read_reg(client, LM87_REG_ALARMS1, &first);
+ if (ret < 0)
+ goto error;
+ ret = lm87_read_reg(client, LM87_REG_ALARMS2, &second);
+ if (ret < 0) {
+ data->pending_alarms |= first;
+ goto error;
+ }
+ data->alarms = data->pending_alarms | first | second << 8;
+ data->pending_alarms = 0;
data->last_updated = jiffies;
data->valid = true;
@@ -263,6 +327,11 @@ static struct lm87_data *lm87_update_device(struct device *dev)
mutex_unlock(&data->update_lock);
return data;
+
+error:
+ data->valid = false;
+ mutex_unlock(&data->update_lock);
+ return ERR_PTR(ret);
}
/*
@@ -275,6 +344,9 @@ static ssize_t in_input_show(struct device *dev,
struct lm87_data *data = lm87_update_device(dev);
int nr = to_sensor_dev_attr(attr)->index;
+ if (IS_ERR(data))
+ return PTR_ERR(data);
+
return sprintf(buf, "%u\n", IN_FROM_REG(data->in[nr],
data->in_scale[nr]));
}
@@ -285,6 +357,9 @@ static ssize_t in_min_show(struct device *dev, struct device_attribute *attr,
struct lm87_data *data = lm87_update_device(dev);
int nr = to_sensor_dev_attr(attr)->index;
+ if (IS_ERR(data))
+ return PTR_ERR(data);
+
return sprintf(buf, "%u\n", IN_FROM_REG(data->in_min[nr],
data->in_scale[nr]));
}
@@ -295,6 +370,9 @@ static ssize_t in_max_show(struct device *dev, struct device_attribute *attr,
struct lm87_data *data = lm87_update_device(dev);
int nr = to_sensor_dev_attr(attr)->index;
+ if (IS_ERR(data))
+ return PTR_ERR(data);
+
return sprintf(buf, "%u\n", IN_FROM_REG(data->in_max[nr],
data->in_scale[nr]));
}
@@ -378,6 +456,9 @@ static ssize_t temp_input_show(struct device *dev,
struct lm87_data *data = lm87_update_device(dev);
int nr = to_sensor_dev_attr(attr)->index;
+ if (IS_ERR(data))
+ return PTR_ERR(data);
+
return sprintf(buf, "%d\n", TEMP_FROM_REG(data->temp[nr]));
}
@@ -387,6 +468,9 @@ static ssize_t temp_low_show(struct device *dev,
struct lm87_data *data = lm87_update_device(dev);
int nr = to_sensor_dev_attr(attr)->index;
+ if (IS_ERR(data))
+ return PTR_ERR(data);
+
return sprintf(buf, "%d\n",
TEMP_FROM_REG(data->temp_low[nr]));
}
@@ -397,6 +481,9 @@ static ssize_t temp_high_show(struct device *dev,
struct lm87_data *data = lm87_update_device(dev);
int nr = to_sensor_dev_attr(attr)->index;
+ if (IS_ERR(data))
+ return PTR_ERR(data);
+
return sprintf(buf, "%d\n",
TEMP_FROM_REG(data->temp_high[nr]));
}
@@ -463,6 +550,9 @@ static ssize_t temp1_crit_show(struct device *dev,
struct device_attribute *attr, char *buf)
{
struct lm87_data *data = lm87_update_device(dev);
+ if (IS_ERR(data))
+ return PTR_ERR(data);
+
return sprintf(buf, "%d\n", TEMP_FROM_REG(data->temp_crit_int));
}
@@ -470,6 +560,9 @@ static ssize_t temp2_crit_show(struct device *dev,
struct device_attribute *attr, char *buf)
{
struct lm87_data *data = lm87_update_device(dev);
+ if (IS_ERR(data))
+ return PTR_ERR(data);
+
return sprintf(buf, "%d\n", TEMP_FROM_REG(data->temp_crit_ext));
}
@@ -483,6 +576,9 @@ static ssize_t fan_input_show(struct device *dev,
struct lm87_data *data = lm87_update_device(dev);
int nr = to_sensor_dev_attr(attr)->index;
+ if (IS_ERR(data))
+ return PTR_ERR(data);
+
return sprintf(buf, "%d\n", fan_from_reg(data->fan[nr],
FAN_DIV_FROM_REG(data->fan_div[nr])));
}
@@ -493,6 +589,9 @@ static ssize_t fan_min_show(struct device *dev, struct device_attribute *attr,
struct lm87_data *data = lm87_update_device(dev);
int nr = to_sensor_dev_attr(attr)->index;
+ if (IS_ERR(data))
+ return PTR_ERR(data);
+
return sprintf(buf, "%d\n", fan_from_reg(data->fan_min[nr],
FAN_DIV_FROM_REG(data->fan_div[nr])));
}
@@ -503,6 +602,9 @@ static ssize_t fan_div_show(struct device *dev, struct device_attribute *attr,
struct lm87_data *data = lm87_update_device(dev);
int nr = to_sensor_dev_attr(attr)->index;
+ if (IS_ERR(data))
+ return PTR_ERR(data);
+
return sprintf(buf, "%d\n",
FAN_DIV_FROM_REG(data->fan_div[nr]));
}
@@ -613,6 +715,9 @@ static ssize_t alarms_show(struct device *dev, struct device_attribute *attr,
char *buf)
{
struct lm87_data *data = lm87_update_device(dev);
+ if (IS_ERR(data))
+ return PTR_ERR(data);
+
return sprintf(buf, "%d\n", data->alarms);
}
static DEVICE_ATTR_RO(alarms);
@@ -621,6 +726,9 @@ static ssize_t cpu0_vid_show(struct device *dev,
struct device_attribute *attr, char *buf)
{
struct lm87_data *data = lm87_update_device(dev);
+ if (IS_ERR(data))
+ return PTR_ERR(data);
+
return sprintf(buf, "%d\n", vid_from_reg(data->vid, data->vrm));
}
static DEVICE_ATTR_RO(cpu0_vid);
@@ -654,6 +762,9 @@ static ssize_t aout_output_show(struct device *dev,
struct device_attribute *attr, char *buf)
{
struct lm87_data *data = lm87_update_device(dev);
+ if (IS_ERR(data))
+ return PTR_ERR(data);
+
return sprintf(buf, "%d\n", AOUT_FROM_REG(data->aout));
}
static ssize_t aout_output_store(struct device *dev,
@@ -686,6 +797,9 @@ static ssize_t alarm_show(struct device *dev, struct device_attribute *attr,
{
struct lm87_data *data = lm87_update_device(dev);
int bitnr = to_sensor_dev_attr(attr)->index;
+ if (IS_ERR(data))
+ return PTR_ERR(data);
+
return sprintf(buf, "%u\n", (data->alarms >> bitnr) & 1);
}
static SENSOR_DEVICE_ATTR_RO(in0_alarm, alarm, 0);
--
2.55.0