TMP117 on PSC is not a temperature sensor

root@oxz_switch0:~# faux-mgs --interface psc0 inventory
Jun 03 17:23:17.951 INFO creating SP handle on interface psc0, component: faux-mgs
Jun 03 17:23:17.952 INFO initial discovery complete, addr: [fe80::aa40:25ff:fe06:107%76]:11111, interface: psc0, socket: control-plane-agent, component: faux-mgs
COMPONENT        STATUS       DEVICE           DESCRIPTION (CAPABILITIES)
sp               Present      sp               Service Processor (DeviceCapabilities(1))
system-led       Present      system-led       System attention LED (DeviceCapabilities(8))
U31              Present      tmp116           Temperature sensor (DeviceCapabilities(0))
U32              Present      at24csw080       FRU ID EEPROM (DeviceCapabilities(0))
PSU0/ID          Present      m24c02           PSU 0 EEPROM (DeviceCapabilities(0))
PSU0             Present      mwocp68          PSU 0 MCU (DeviceCapabilities(2))
PSU1/ID          Present      m24c02           PSU 1 EEPROM (DeviceCapabilities(0))
PSU1             Present      mwocp68          PSU 1 MCU (DeviceCapabilities(2))
PSU2/ID          Present      m24c02           PSU 2 EEPROM (DeviceCapabilities(0))
PSU2             Present      mwocp68          PSU 2 MCU (DeviceCapabilities(2))
PSU3/ID          NotPresent   m24c02           PSU 3 EEPROM (DeviceCapabilities(0))
PSU3             NotPresent   mwocp68          PSU 3 MCU (DeviceCapabilities(2))
PSU4/ID          NotPresent   m24c02           PSU 4 EEPROM (DeviceCapabilities(0))
PSU4             NotPresent   mwocp68          PSU 4 MCU (DeviceCapabilities(2))
PSU5/ID          NotPresent   m24c02           PSU 5 EEPROM (DeviceCapabilities(0))
PSU5             NotPresent   mwocp68          PSU 5 MCU (DeviceCapabilities(2))
root@oxz_switch0:~# faux-mgs --interface psc0 component-details U31
Jun 03 17:23:45.766 INFO creating SP handle on interface psc0, component: faux-mgs
Jun 03 17:23:45.802 INFO initial discovery complete, addr: [fe80::aa40:25ff:fe06:107%76]:11111, interface: psc0, socket: control-plane-agent, component: faux-mgs
root@oxz_switch0:~#

Note that U31 does not have the DeviceCapabilities bit for HAS_MEASUREMENT_CHANNELS. When I try to actually read its component details, I don't get any details.

I believe this is because the config for the temperature sensor on the PSC looks like this:

https://github.com/oxidecomputer/hubris/blob/8f5e0f7c2417aa70a341120cc02c4ceb581156af/app/psc/base.toml#L382-L387

In contrast to a board like Gimlet, where it looks like this:

https://github.com/oxidecomputer/hubris/blob/8f5e0f7c2417aa70a341120cc02c4ceb581156af/app/gimlet/base.toml#L442-L450

Note that:

• We don't have a sensors config on PSC, so the I2C sensor codegen doesn't know it's a sensor
• We also say it's a tmp116 instead of a tmp117. While I believe these parts are pretty similar, the Hubris driver for the temperature sensor is called tmp117, and I bet that if we added a sensor config here it wouldn't build because there's no drv_i2c_devices module called tmp116
• PSC also doesn't have a thermal loop, so we might need to add something in sensor-polling to actually tell it to read from the sensor, as well.

Compare the PSC temperature-sensor configuration in app/psc/base.toml with the sensor configuration in app/gimlet/base.toml, including the tmp116/tmp117 device name. Read the related sensor-polling code to determine how PSC should read U31 without a thermal loop. Done means U31 exposes HAS_MEASUREMENT_CHANNELS and faux-mgs component-details returns its measurement data.