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- Naming and data format standards for sysfs files
- ================================================
- The libsensors library offers an interface to the raw sensors data
- through the sysfs interface. Since lm-sensors 3.0.0, libsensors is
- completely chip-independent. It assumes that all the kernel drivers
- implement the standard sysfs interface described in this document.
- This makes adding or updating support for any given chip very easy, as
- libsensors, and applications using it, do not need to be modified.
- This is a major improvement compared to lm-sensors 2.
- Note that motherboards vary widely in the connections to sensor chips.
- There is no standard that ensures, for example, that the second
- temperature sensor is connected to the CPU, or that the second fan is on
- the CPU. Also, some values reported by the chips need some computation
- before they make full sense. For example, most chips can only measure
- voltages between 0 and +4V. Other voltages are scaled back into that
- range using external resistors. Since the values of these resistors
- can change from motherboard to motherboard, the conversions cannot be
- hard coded into the driver and have to be done in user space.
- For this reason, even if we aim at a chip-independent libsensors, it will
- still require a configuration file (e.g. /etc/sensors.conf) for proper
- values conversion, labeling of inputs and hiding of unused inputs.
- An alternative method that some programs use is to access the sysfs
- files directly. This document briefly describes the standards that the
- drivers follow, so that an application program can scan for entries and
- access this data in a simple and consistent way. That said, such programs
- will have to implement conversion, labeling and hiding of inputs. For
- this reason, it is still not recommended to bypass the library.
- Each chip gets its own directory in the sysfs /sys/devices tree. To
- find all sensor chips, it is easier to follow the device symlinks from
- `/sys/class/hwmon/hwmon*`.
- Up to lm-sensors 3.0.0, libsensors looks for hardware monitoring attributes
- in the "physical" device directory. Since lm-sensors 3.0.1, attributes found
- in the hwmon "class" device directory are also supported. Complex drivers
- (e.g. drivers for multifunction chips) may want to use this possibility to
- avoid namespace pollution. The only drawback will be that older versions of
- libsensors won't support the driver in question.
- All sysfs values are fixed point numbers.
- There is only one value per file, unlike the older /proc specification.
- The common scheme for files naming is: <type><number>_<item>. Usual
- types for sensor chips are "in" (voltage), "temp" (temperature) and
- "fan" (fan). Usual items are "input" (measured value), "max" (high
- threshold, "min" (low threshold). Numbering usually starts from 1,
- except for voltages which start from 0 (because most data sheets use
- this). A number is always used for elements that can be present more
- than once, even if there is a single element of the given type on the
- specific chip. Other files do not refer to a specific element, so
- they have a simple name, and no number.
- Alarms are direct indications read from the chips. The drivers do NOT
- make comparisons of readings to thresholds. This allows violations
- between readings to be caught and alarmed. The exact definition of an
- alarm (for example, whether a threshold must be met or must be exceeded
- to cause an alarm) is chip-dependent.
- When setting values of hwmon sysfs attributes, the string representation of
- the desired value must be written, note that strings which are not a number
- are interpreted as 0! For more on how written strings are interpreted see the
- "sysfs attribute writes interpretation" section at the end of this file.
- -------------------------------------------------------------------------
- ======= ===========================================
- `[0-*]` denotes any positive number starting from 0
- `[1-*]` denotes any positive number starting from 1
- RO read only value
- WO write only value
- RW read/write value
- ======= ===========================================
- Read/write values may be read-only for some chips, depending on the
- hardware implementation.
- All entries (except name) are optional, and should only be created in a
- given driver if the chip has the feature.
- *****************
- Global attributes
- *****************
- `name`
- The chip name.
- This should be a short, lowercase string, not containing
- whitespace, dashes, or the wildcard character '*'.
- This attribute represents the chip name. It is the only
- mandatory attribute.
- I2C devices get this attribute created automatically.
- RO
- `update_interval`
- The interval at which the chip will update readings.
- Unit: millisecond
- RW
- Some devices have a variable update rate or interval.
- This attribute can be used to change it to the desired value.
- ********
- Voltages
- ********
- `in[0-*]_min`
- Voltage min value.
- Unit: millivolt
- RW
- `in[0-*]_lcrit`
- Voltage critical min value.
- Unit: millivolt
- RW
- If voltage drops to or below this limit, the system may
- take drastic action such as power down or reset. At the very
- least, it should report a fault.
- `in[0-*]_max`
- Voltage max value.
- Unit: millivolt
- RW
- `in[0-*]_crit`
- Voltage critical max value.
- Unit: millivolt
- RW
- If voltage reaches or exceeds this limit, the system may
- take drastic action such as power down or reset. At the very
- least, it should report a fault.
- `in[0-*]_input`
- Voltage input value.
- Unit: millivolt
- RO
- Voltage measured on the chip pin.
- Actual voltage depends on the scaling resistors on the
- motherboard, as recommended in the chip datasheet.
- This varies by chip and by motherboard.
- Because of this variation, values are generally NOT scaled
- by the chip driver, and must be done by the application.
- However, some drivers (notably lm87 and via686a)
- do scale, because of internal resistors built into a chip.
- These drivers will output the actual voltage. Rule of
- thumb: drivers should report the voltage values at the
- "pins" of the chip.
- `in[0-*]_average`
- Average voltage
- Unit: millivolt
- RO
- `in[0-*]_lowest`
- Historical minimum voltage
- Unit: millivolt
- RO
- `in[0-*]_highest`
- Historical maximum voltage
- Unit: millivolt
- RO
- `in[0-*]_reset_history`
- Reset inX_lowest and inX_highest
- WO
- `in_reset_history`
- Reset inX_lowest and inX_highest for all sensors
- WO
- `in[0-*]_label`
- Suggested voltage channel label.
- Text string
- Should only be created if the driver has hints about what
- this voltage channel is being used for, and user-space
- doesn't. In all other cases, the label is provided by
- user-space.
- RO
- `in[0-*]_enable`
- Enable or disable the sensors.
- When disabled the sensor read will return -ENODATA.
- - 1: Enable
- - 0: Disable
- RW
- `cpu[0-*]_vid`
- CPU core reference voltage.
- Unit: millivolt
- RO
- Not always correct.
- `vrm`
- Voltage Regulator Module version number.
- RW (but changing it should no more be necessary)
- Originally the VRM standard version multiplied by 10, but now
- an arbitrary number, as not all standards have a version
- number.
- Affects the way the driver calculates the CPU core reference
- voltage from the vid pins.
- `in[0-*]_rated_min`
- Minimum rated voltage.
- Unit: millivolt
- RO
- `in[0-*]_rated_max`
- Maximum rated voltage.
- Unit: millivolt
- RO
- Also see the Alarms section for status flags associated with voltages.
- ****
- Fans
- ****
- `fan[1-*]_min`
- Fan minimum value
- Unit: revolution/min (RPM)
- RW
- `fan[1-*]_max`
- Fan maximum value
- Unit: revolution/min (RPM)
- Only rarely supported by the hardware.
- RW
- `fan[1-*]_input`
- Fan input value.
- Unit: revolution/min (RPM)
- RO
- `fan[1-*]_div`
- Fan divisor.
- Integer value in powers of two (1, 2, 4, 8, 16, 32, 64, 128).
- RW
- Some chips only support values 1, 2, 4 and 8.
- Note that this is actually an internal clock divisor, which
- affects the measurable speed range, not the read value.
- `fan[1-*]_pulses`
- Number of tachometer pulses per fan revolution.
- Integer value, typically between 1 and 4.
- RW
- This value is a characteristic of the fan connected to the
- device's input, so it has to be set in accordance with the fan
- model.
- Should only be created if the chip has a register to configure
- the number of pulses. In the absence of such a register (and
- thus attribute) the value assumed by all devices is 2 pulses
- per fan revolution.
- `fan[1-*]_target`
- Desired fan speed
- Unit: revolution/min (RPM)
- RW
- Only makes sense if the chip supports closed-loop fan speed
- control based on the measured fan speed.
- `fan[1-*]_label`
- Suggested fan channel label.
- Text string
- Should only be created if the driver has hints about what
- this fan channel is being used for, and user-space doesn't.
- In all other cases, the label is provided by user-space.
- RO
- `fan[1-*]_enable`
- Enable or disable the sensors.
- When disabled the sensor read will return -ENODATA.
- - 1: Enable
- - 0: Disable
- RW
- Also see the Alarms section for status flags associated with fans.
- ***
- PWM
- ***
- `pwm[1-*]`
- Pulse width modulation fan control.
- Integer value in the range 0 to 255
- RW
- 255 is max or 100%.
- `pwm[1-*]_enable`
- Fan speed control method:
- - 0: no fan speed control (i.e. fan at full speed)
- - 1: manual fan speed control enabled (using `pwm[1-*]`)
- - 2+: automatic fan speed control enabled
- Check individual chip documentation files for automatic mode
- details.
- RW
- `pwm[1-*]_mode`
- - 0: DC mode (direct current)
- - 1: PWM mode (pulse-width modulation)
- RW
- `pwm[1-*]_freq`
- Base PWM frequency in Hz.
- Only possibly available when pwmN_mode is PWM, but not always
- present even then.
- RW
- `pwm[1-*]_auto_channels_temp`
- Select which temperature channels affect this PWM output in
- auto mode.
- Bitfield, 1 is temp1, 2 is temp2, 4 is temp3 etc...
- Which values are possible depend on the chip used.
- RW
- `pwm[1-*]_auto_point[1-*]_pwm` / `pwm[1-*]_auto_point[1-*]_temp` / `pwm[1-*]_auto_point[1-*]_temp_hyst`
- Define the PWM vs temperature curve.
- Number of trip points is chip-dependent. Use this for chips
- which associate trip points to PWM output channels.
- RW
- `temp[1-*]_auto_point[1-*]_pwm` / `temp[1-*]_auto_point[1-*]_temp` / `temp[1-*]_auto_point[1-*]_temp_hyst`
- Define the PWM vs temperature curve.
- Number of trip points is chip-dependent. Use this for chips
- which associate trip points to temperature channels.
- RW
- There is a third case where trip points are associated to both PWM output
- channels and temperature channels: the PWM values are associated to PWM
- output channels while the temperature values are associated to temperature
- channels. In that case, the result is determined by the mapping between
- temperature inputs and PWM outputs. When several temperature inputs are
- mapped to a given PWM output, this leads to several candidate PWM values.
- The actual result is up to the chip, but in general the highest candidate
- value (fastest fan speed) wins.
- ************
- Temperatures
- ************
- `temp[1-*]_type`
- Sensor type selection.
- Integers 1 to 6
- RW
- - 1: CPU embedded diode
- - 2: 3904 transistor
- - 3: thermal diode
- - 4: thermistor
- - 5: AMD AMDSI
- - 6: Intel PECI
- Not all types are supported by all chips
- `temp[1-*]_max`
- Temperature max value.
- Unit: millidegree Celsius (or millivolt, see below)
- RW
- `temp[1-*]_min`
- Temperature min value.
- Unit: millidegree Celsius
- RW
- `temp[1-*]_max_hyst`
- Temperature hysteresis value for max limit.
- Unit: millidegree Celsius
- Must be reported as an absolute temperature, NOT a delta
- from the max value.
- RW
- `temp[1-*]_min_hyst`
- Temperature hysteresis value for min limit.
- Unit: millidegree Celsius
- Must be reported as an absolute temperature, NOT a delta
- from the min value.
- RW
- `temp[1-*]_input`
- Temperature input value.
- Unit: millidegree Celsius
- RO
- `temp[1-*]_crit`
- Temperature critical max value, typically greater than
- corresponding temp_max values.
- Unit: millidegree Celsius
- RW
- `temp[1-*]_crit_hyst`
- Temperature hysteresis value for critical limit.
- Unit: millidegree Celsius
- Must be reported as an absolute temperature, NOT a delta
- from the critical value.
- RW
- `temp[1-*]_emergency`
- Temperature emergency max value, for chips supporting more than
- two upper temperature limits. Must be equal or greater than
- corresponding temp_crit values.
- Unit: millidegree Celsius
- RW
- `temp[1-*]_emergency_hyst`
- Temperature hysteresis value for emergency limit.
- Unit: millidegree Celsius
- Must be reported as an absolute temperature, NOT a delta
- from the emergency value.
- RW
- `temp[1-*]_lcrit`
- Temperature critical min value, typically lower than
- corresponding temp_min values.
- Unit: millidegree Celsius
- RW
- `temp[1-*]_lcrit_hyst`
- Temperature hysteresis value for critical min limit.
- Unit: millidegree Celsius
- Must be reported as an absolute temperature, NOT a delta
- from the critical min value.
- RW
- `temp[1-*]_offset`
- Temperature offset which is added to the temperature reading
- by the chip.
- Unit: millidegree Celsius
- Read/Write value.
- `temp[1-*]_label`
- Suggested temperature channel label.
- Text string
- Should only be created if the driver has hints about what
- this temperature channel is being used for, and user-space
- doesn't. In all other cases, the label is provided by
- user-space.
- RO
- `temp[1-*]_lowest`
- Historical minimum temperature
- Unit: millidegree Celsius
- RO
- `temp[1-*]_highest`
- Historical maximum temperature
- Unit: millidegree Celsius
- RO
- `temp[1-*]_reset_history`
- Reset temp_lowest and temp_highest
- WO
- `temp_reset_history`
- Reset temp_lowest and temp_highest for all sensors
- WO
- `temp[1-*]_enable`
- Enable or disable the sensors.
- When disabled the sensor read will return -ENODATA.
- - 1: Enable
- - 0: Disable
- RW
- `temp[1-*]_rated_min`
- Minimum rated temperature.
- Unit: millidegree Celsius
- RO
- `temp[1-*]_rated_max`
- Maximum rated temperature.
- Unit: millidegree Celsius
- RO
- Some chips measure temperature using external thermistors and an ADC, and
- report the temperature measurement as a voltage. Converting this voltage
- back to a temperature (or the other way around for limits) requires
- mathematical functions not available in the kernel, so the conversion
- must occur in user space. For these chips, all temp* files described
- above should contain values expressed in millivolt instead of millidegree
- Celsius. In other words, such temperature channels are handled as voltage
- channels by the driver.
- Also see the Alarms section for status flags associated with temperatures.
- ********
- Currents
- ********
- `curr[1-*]_max`
- Current max value
- Unit: milliampere
- RW
- `curr[1-*]_min`
- Current min value.
- Unit: milliampere
- RW
- `curr[1-*]_lcrit`
- Current critical low value
- Unit: milliampere
- RW
- `curr[1-*]_crit`
- Current critical high value.
- Unit: milliampere
- RW
- `curr[1-*]_input`
- Current input value
- Unit: milliampere
- RO
- `curr[1-*]_average`
- Average current use
- Unit: milliampere
- RO
- `curr[1-*]_lowest`
- Historical minimum current
- Unit: milliampere
- RO
- `curr[1-*]_highest`
- Historical maximum current
- Unit: milliampere
- RO
- `curr[1-*]_reset_history`
- Reset currX_lowest and currX_highest
- WO
- `curr_reset_history`
- Reset currX_lowest and currX_highest for all sensors
- WO
- `curr[1-*]_enable`
- Enable or disable the sensors.
- When disabled the sensor read will return -ENODATA.
- - 1: Enable
- - 0: Disable
- RW
- `curr[1-*]_rated_min`
- Minimum rated current.
- Unit: milliampere
- RO
- `curr[1-*]_rated_max`
- Maximum rated current.
- Unit: milliampere
- RO
- Also see the Alarms section for status flags associated with currents.
- *****
- Power
- *****
- `power[1-*]_average`
- Average power use
- Unit: microWatt
- RO
- `power[1-*]_average_interval`
- Power use averaging interval. A poll
- notification is sent to this file if the
- hardware changes the averaging interval.
- Unit: milliseconds
- RW
- `power[1-*]_average_interval_max`
- Maximum power use averaging interval
- Unit: milliseconds
- RO
- `power[1-*]_average_interval_min`
- Minimum power use averaging interval
- Unit: milliseconds
- RO
- `power[1-*]_average_highest`
- Historical average maximum power use
- Unit: microWatt
- RO
- `power[1-*]_average_lowest`
- Historical average minimum power use
- Unit: microWatt
- RO
- `power[1-*]_average_max`
- A poll notification is sent to
- `power[1-*]_average` when power use
- rises above this value.
- Unit: microWatt
- RW
- `power[1-*]_average_min`
- A poll notification is sent to
- `power[1-*]_average` when power use
- sinks below this value.
- Unit: microWatt
- RW
- `power[1-*]_input`
- Instantaneous power use
- Unit: microWatt
- RO
- `power[1-*]_input_highest`
- Historical maximum power use
- Unit: microWatt
- RO
- `power[1-*]_input_lowest`
- Historical minimum power use
- Unit: microWatt
- RO
- `power[1-*]_reset_history`
- Reset input_highest, input_lowest,
- average_highest and average_lowest.
- WO
- `power[1-*]_accuracy`
- Accuracy of the power meter.
- Unit: Percent
- RO
- `power[1-*]_cap`
- If power use rises above this limit, the
- system should take action to reduce power use.
- A poll notification is sent to this file if the
- cap is changed by the hardware. The `*_cap`
- files only appear if the cap is known to be
- enforced by hardware.
- Unit: microWatt
- RW
- `power[1-*]_cap_hyst`
- Margin of hysteresis built around capping and
- notification.
- Unit: microWatt
- RW
- `power[1-*]_cap_max`
- Maximum cap that can be set.
- Unit: microWatt
- RO
- `power[1-*]_cap_min`
- Minimum cap that can be set.
- Unit: microWatt
- RO
- `power[1-*]_max`
- Maximum power.
- Unit: microWatt
- RW
- `power[1-*]_crit`
- Critical maximum power.
- If power rises to or above this limit, the
- system is expected take drastic action to reduce
- power consumption, such as a system shutdown or
- a forced powerdown of some devices.
- Unit: microWatt
- RW
- `power[1-*]_enable`
- Enable or disable the sensors.
- When disabled the sensor read will return
- -ENODATA.
- - 1: Enable
- - 0: Disable
- RW
- `power[1-*]_rated_min`
- Minimum rated power.
- Unit: microWatt
- RO
- `power[1-*]_rated_max`
- Maximum rated power.
- Unit: microWatt
- RO
- Also see the Alarms section for status flags associated with power readings.
- ******
- Energy
- ******
- `energy[1-*]_input`
- Cumulative energy use
- Unit: microJoule
- RO
- `energy[1-*]_enable`
- Enable or disable the sensors.
- When disabled the sensor read will return
- -ENODATA.
- - 1: Enable
- - 0: Disable
- RW
- ********
- Humidity
- ********
- `humidity[1-*]_input`
- Humidity
- Unit: milli-percent (per cent mille, pcm)
- RO
- `humidity[1-*]_enable`
- Enable or disable the sensors
- When disabled the sensor read will return
- -ENODATA.
- - 1: Enable
- - 0: Disable
- RW
- `humidity[1-*]_rated_min`
- Minimum rated humidity.
- Unit: milli-percent (per cent mille, pcm)
- RO
- `humidity[1-*]_rated_max`
- Maximum rated humidity.
- Unit: milli-percent (per cent mille, pcm)
- RO
- ******
- Alarms
- ******
- Each channel or limit may have an associated alarm file, containing a
- boolean value. 1 means than an alarm condition exists, 0 means no alarm.
- Usually a given chip will either use channel-related alarms, or
- limit-related alarms, not both. The driver should just reflect the hardware
- implementation.
- +-------------------------------+-----------------------+
- | **`in[0-*]_alarm`, | Channel alarm |
- | `curr[1-*]_alarm`, | |
- | `power[1-*]_alarm`, | - 0: no alarm |
- | `fan[1-*]_alarm`, | - 1: alarm |
- | `temp[1-*]_alarm`** | |
- | | RO |
- +-------------------------------+-----------------------+
- **OR**
- +-------------------------------+-----------------------+
- | **`in[0-*]_min_alarm`, | Limit alarm |
- | `in[0-*]_max_alarm`, | |
- | `in[0-*]_lcrit_alarm`, | - 0: no alarm |
- | `in[0-*]_crit_alarm`, | - 1: alarm |
- | `curr[1-*]_min_alarm`, | |
- | `curr[1-*]_max_alarm`, | RO |
- | `curr[1-*]_lcrit_alarm`, | |
- | `curr[1-*]_crit_alarm`, | |
- | `power[1-*]_cap_alarm`, | |
- | `power[1-*]_max_alarm`, | |
- | `power[1-*]_crit_alarm`, | |
- | `fan[1-*]_min_alarm`, | |
- | `fan[1-*]_max_alarm`, | |
- | `temp[1-*]_min_alarm`, | |
- | `temp[1-*]_max_alarm`, | |
- | `temp[1-*]_lcrit_alarm`, | |
- | `temp[1-*]_crit_alarm`, | |
- | `temp[1-*]_emergency_alarm`** | |
- +-------------------------------+-----------------------+
- Each input channel may have an associated fault file. This can be used
- to notify open diodes, unconnected fans etc. where the hardware
- supports it. When this boolean has value 1, the measurement for that
- channel should not be trusted.
- `fan[1-*]_fault` / `temp[1-*]_fault`
- Input fault condition
- - 0: no fault occurred
- - 1: fault condition
- RO
- Some chips also offer the possibility to get beeped when an alarm occurs:
- `beep_enable`
- Master beep enable
- - 0: no beeps
- - 1: beeps
- RW
- `in[0-*]_beep`, `curr[1-*]_beep`, `fan[1-*]_beep`, `temp[1-*]_beep`,
- Channel beep
- - 0: disable
- - 1: enable
- RW
- In theory, a chip could provide per-limit beep masking, but no such chip
- was seen so far.
- Old drivers provided a different, non-standard interface to alarms and
- beeps. These interface files are deprecated, but will be kept around
- for compatibility reasons:
- `alarms`
- Alarm bitmask.
- RO
- Integer representation of one to four bytes.
- A '1' bit means an alarm.
- Chips should be programmed for 'comparator' mode so that
- the alarm will 'come back' after you read the register
- if it is still valid.
- Generally a direct representation of a chip's internal
- alarm registers; there is no standard for the position
- of individual bits. For this reason, the use of this
- interface file for new drivers is discouraged. Use
- `individual *_alarm` and `*_fault` files instead.
- Bits are defined in kernel/include/sensors.h.
- `beep_mask`
- Bitmask for beep.
- Same format as 'alarms' with the same bit locations,
- use discouraged for the same reason. Use individual
- `*_beep` files instead.
- RW
- *******************
- Intrusion detection
- *******************
- `intrusion[0-*]_alarm`
- Chassis intrusion detection
- - 0: OK
- - 1: intrusion detected
- RW
- Contrary to regular alarm flags which clear themselves
- automatically when read, this one sticks until cleared by
- the user. This is done by writing 0 to the file. Writing
- other values is unsupported.
- `intrusion[0-*]_beep`
- Chassis intrusion beep
- 0: disable
- 1: enable
- RW
- ****************************
- Average sample configuration
- ****************************
- Devices allowing for reading {in,power,curr,temp}_average values may export
- attributes for controlling number of samples used to compute average.
- +--------------+---------------------------------------------------------------+
- | samples | Sets number of average samples for all types of measurements. |
- | | |
- | | RW |
- +--------------+---------------------------------------------------------------+
- | in_samples | Sets number of average samples for specific type of |
- | power_samples| measurements. |
- | curr_samples | |
- | temp_samples | Note that on some devices it won't be possible to set all of |
- | | them to different values so changing one might also change |
- | | some others. |
- | | |
- | | RW |
- +--------------+---------------------------------------------------------------+
- sysfs attribute writes interpretation
- -------------------------------------
- hwmon sysfs attributes always contain numbers, so the first thing to do is to
- convert the input to a number, there are 2 ways todo this depending whether
- the number can be negative or not::
- unsigned long u = simple_strtoul(buf, NULL, 10);
- long s = simple_strtol(buf, NULL, 10);
- With buf being the buffer with the user input being passed by the kernel.
- Notice that we do not use the second argument of strto[u]l, and thus cannot
- tell when 0 is returned, if this was really 0 or is caused by invalid input.
- This is done deliberately as checking this everywhere would add a lot of
- code to the kernel.
- Notice that it is important to always store the converted value in an
- unsigned long or long, so that no wrap around can happen before any further
- checking.
- After the input string is converted to an (unsigned) long, the value should be
- checked if its acceptable. Be careful with further conversions on the value
- before checking it for validity, as these conversions could still cause a wrap
- around before the check. For example do not multiply the result, and only
- add/subtract if it has been divided before the add/subtract.
- What to do if a value is found to be invalid, depends on the type of the
- sysfs attribute that is being set. If it is a continuous setting like a
- tempX_max or inX_max attribute, then the value should be clamped to its
- limits using clamp_val(value, min_limit, max_limit). If it is not continuous
- like for example a tempX_type, then when an invalid value is written,
- -EINVAL should be returned.
- Example1, temp1_max, register is a signed 8 bit value (-128 - 127 degrees)::
- long v = simple_strtol(buf, NULL, 10) / 1000;
- v = clamp_val(v, -128, 127);
- /* write v to register */
- Example2, fan divider setting, valid values 2, 4 and 8::
- unsigned long v = simple_strtoul(buf, NULL, 10);
- switch (v) {
- case 2: v = 1; break;
- case 4: v = 2; break;
- case 8: v = 3; break;
- default:
- return -EINVAL;
- }
- /* write v to register */
|