1# Sensor Config
2
3This program is only meant to control fans given thermal sensor readings.
4
5All sensors in phosphor-dbus-interfaces for OpenBMC use Sensor.Value as their
6accessor. This provides read-only access to information. The goal of the
7configuration is to specify how it can be read and if it's a fan, how the PID
8output can be written. Initially there'll only be sysfs and passive dbus
9access. If a writePath for a sensor is a dbus path, then the system will need
10to verify which Control.Fan* interfaces is registered and send values to the
11Target property of that interface.
12
13The min/max specified are to range a writePercent to the sensor. The current
14FanController object outputs the new fan speed goal as a PWM percentage. Other
15fan PID control objects may not, and they can leave the fields as 0 & 0.
16
17The only requirement for a sensor is that it isn't writeonly. Only fans are
18expected to have a writePath set, and in this current version non-fan sensors
19are assumed readonly.
20
21The sensor names are unique across all zones.
22
23"sensors" : [
24 {
25 "name": "fan1", /* Name of the sensor. */
26 "type": "fan", /* Type of sensor, fan, temp, margin */
27 "readPath": "", /* How the sensor can be read[1] */
28 "writePath": "", /* How the sensor can be set[2] */
29 "min": 0, /* The minimum value used for scaling writes (int64) */
30 "max": 255, /* The maximum value used for scaling writes (int64) */
31 "timeout": 0 /* The timeout value for the sensor, used for failsafe, 0
32 * means no timeout (int64) */
33 },
34]
35
36[1] readPath has multiple options:
37* If it has "/xyz/openbmc_project/extsensors/" in it, it's an EXTERNAL or
38 host-provided sensor.
39* If it has "/xyz/openbmc_project/" in it, it's a sensor whose value is
40 received passively over dbus.
41* If it has "/sys/" in it, it's a sensor read directly from sysfs.
42
43[2]
44* This can be left blank if the sensor is read-only.
45* If it has "/sys/" in it, it's a sensor written to sysfs.
46 * If min and max are non-zero, it'll convert the value to within the range.
47 and output that modified value. So, if it receives a value of .90 and min
48 is 0, and max is 255, it'll convert that to a value of 229.5 that is then
49 cast to int64_t.
50
51# PID Config
52
53The PID configuration is a list of PIDs per zone.
54
55"zones" : [
56 {
57 "id": 1, /* zone id. */
58 "minThermalOutput": 3000.0, /* The minimum thermal RPM value. (double) */
59 "failsafePercent": 75.0, /* The percent to use when the zone is in fail-safe mode. (double) */
60 "pids": [
61 {
62 "name": "fan1-5", /* PID name */
63 "type": "fan", /* Type of PID, fan, temp, or margin. */
64 "inputs": ["fan1", "fan5"], /* Sensor names that are inputs for the PID */
65 "setpoint": 90.0, /* For temp/margin PIDs this is the setpoint, ignored otherwise (double) */
66 "pid": {
67 "samplePeriod": 0.1, /* The input sample period. (double) */
68 "proportionalCoeff": 0.0, /* The proportional coefficient. (double) */
69 "integralCoeff": 0.0, /* The integral coefficient. (double) */
70 "feedFwdOffsetCoeff": 0.0, /* The feed-forward offset coefficient. (double) */
71 "feedFwdGainCoeff": 0.010, /* The feed-forward gain coefficient. (double) */
72 "integralLimit_min": 0.0, /* The integral limit clamp, min, max (double) */
73 "integralLimit_max": 0.0,
74 "outLim_min": 30.0, /* the PID output clamp, min, max (double) */
75 "outLim_max": 100.0,
76 "slewNeg": 0.0, /* The slew negative value. (double) */
77 "slewPos": 0.0 /* The slew positive value. (double) */
78 }
79 }
80 ]
81 }
82]
83