hwmon: (jc42) do not allow writing to locked registers
On systems where the temperature sensor is actually used, the BIOS is
likely to have locked the alarm registers. In that case, all writes
through the corresponding sysfs files would be silently ignored.
To prevent this, detect the locks and make the affected sysfs files
read-only.
Signed-off-by: Clemens Ladisch <clemens@ladisch.de>
Cc: stable@kernel.org
Signed-off-by: Guenter Roeck <guenter.roeck@ericsson.com>
diff --git a/Documentation/hwmon/jc42 b/Documentation/hwmon/jc42
index 2a09240..a22ecf4 100644
--- a/Documentation/hwmon/jc42
+++ b/Documentation/hwmon/jc42
@@ -86,15 +86,19 @@
which applies to all limits. This register can be written by writing into
temp1_crit_hyst. Other hysteresis attributes are read-only.
+If the BIOS has configured the sensor for automatic temperature management, it
+is likely that it has locked the registers, i.e., that the temperature limits
+cannot be changed.
+
Sysfs entries
-------------
temp1_input Temperature (RO)
-temp1_min Minimum temperature (RW)
-temp1_max Maximum temperature (RW)
-temp1_crit Critical high temperature (RW)
+temp1_min Minimum temperature (RO or RW)
+temp1_max Maximum temperature (RO or RW)
+temp1_crit Critical high temperature (RO or RW)
-temp1_crit_hyst Critical hysteresis temperature (RW)
+temp1_crit_hyst Critical hysteresis temperature (RO or RW)
temp1_max_hyst Maximum hysteresis temperature (RO)
temp1_min_alarm Temperature low alarm
diff --git a/drivers/hwmon/jc42.c b/drivers/hwmon/jc42.c
index 5efe239..9349912 100644
--- a/drivers/hwmon/jc42.c
+++ b/drivers/hwmon/jc42.c
@@ -53,6 +53,8 @@
/* Configuration register defines */
#define JC42_CFG_CRIT_ONLY (1 << 2)
+#define JC42_CFG_TCRIT_LOCK (1 << 6)
+#define JC42_CFG_EVENT_LOCK (1 << 7)
#define JC42_CFG_SHUTDOWN (1 << 8)
#define JC42_CFG_HYST_SHIFT 9
#define JC42_CFG_HYST_MASK 0x03
@@ -380,14 +382,14 @@
static DEVICE_ATTR(temp1_input, S_IRUGO,
show_temp_input, NULL);
-static DEVICE_ATTR(temp1_crit, S_IWUSR | S_IRUGO,
+static DEVICE_ATTR(temp1_crit, S_IRUGO,
show_temp_crit, set_temp_crit);
-static DEVICE_ATTR(temp1_min, S_IWUSR | S_IRUGO,
+static DEVICE_ATTR(temp1_min, S_IRUGO,
show_temp_min, set_temp_min);
-static DEVICE_ATTR(temp1_max, S_IWUSR | S_IRUGO,
+static DEVICE_ATTR(temp1_max, S_IRUGO,
show_temp_max, set_temp_max);
-static DEVICE_ATTR(temp1_crit_hyst, S_IWUSR | S_IRUGO,
+static DEVICE_ATTR(temp1_crit_hyst, S_IRUGO,
show_temp_crit_hyst, set_temp_crit_hyst);
static DEVICE_ATTR(temp1_max_hyst, S_IRUGO,
show_temp_max_hyst, NULL);
@@ -412,8 +414,31 @@
NULL
};
+static mode_t jc42_attribute_mode(struct kobject *kobj,
+ struct attribute *attr, int index)
+{
+ struct device *dev = container_of(kobj, struct device, kobj);
+ struct i2c_client *client = to_i2c_client(dev);
+ struct jc42_data *data = i2c_get_clientdata(client);
+ unsigned int config = data->config;
+ bool readonly;
+
+ if (attr == &dev_attr_temp1_crit.attr)
+ readonly = config & JC42_CFG_TCRIT_LOCK;
+ else if (attr == &dev_attr_temp1_min.attr ||
+ attr == &dev_attr_temp1_max.attr)
+ readonly = config & JC42_CFG_EVENT_LOCK;
+ else if (attr == &dev_attr_temp1_crit_hyst.attr)
+ readonly = config & (JC42_CFG_EVENT_LOCK | JC42_CFG_TCRIT_LOCK);
+ else
+ readonly = true;
+
+ return S_IRUGO | (readonly ? 0 : S_IWUSR);
+}
+
static const struct attribute_group jc42_group = {
.attrs = jc42_attributes,
+ .is_visible = jc42_attribute_mode,
};
/* Return 0 if detection is successful, -ENODEV otherwise */