SFP modules can contain a number of sensors. The EEPROM also contains
recommended alarm and critical values for each sensor, and indications
of if these have been exceeded. Export this information via
HWMON. Currently temperature, VCC, bias current, transmit power, and
possibly receiver power is supported.
The sensors in the modules can either return calibrate or uncalibrated
values. Uncalibrated values need to be manipulated, using coefficients
provided in the SFP EEPROM. Uncalibrated receive power values require
floating point maths in order to calibrate them. Performing this in
the kernel is hard. So if the SFP module indicates it uses
uncalibrated values, RX power is not made available.
With this hwmon device, it is possible to view the sensor values using
lm-sensors programs:
in0: +3.29 V (crit min = +2.90 V, min = +3.00 V)
(max = +3.60 V, crit max = +3.70 V)
temp1: +33.0°C (low = -5.0°C, high = +80.0°C)
(crit low = -10.0°C, crit = +85.0°C)
power1: 1000.00 nW (max = 794.00 uW, min = 50.00 uW) ALARM (LCRIT)
(lcrit = 40.00 uW, crit = 1000.00 uW)
curr1: +0.00 A (crit min = +0.00 A, min = +0.00 A) ALARM (LCRIT, MIN)
(max = +0.01 A, crit max = +0.01 A)
The scaling sensors performs on the bias current is not particularly
good. The raw values are more useful:
curr1:
curr1_input: 0.000
curr1_min: 0.002
curr1_max: 0.010
curr1_lcrit: 0.000
curr1_crit: 0.011
curr1_min_alarm: 1.000
curr1_max_alarm: 0.000
curr1_lcrit_alarm: 1.000
curr1_crit_alarm: 0.000
In order to keep the I2C overhead to a minimum, the constant values,
such as limits and calibration coefficients are read once at module
insertion time. Thus only reading *_input and *_alarm properties
requires i2c read operations.
Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Acked-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
1323061a01