Add device and channel settings api

[zuckschwerdt]

work in progress

[guruofquality]

I was thinking of tagging the master branch soon, is this something we should include?

[zuckschwerdt]

I made an enhancement to SoapySDRUtil --probe to show the sensor values -- interesting for a short time only. Nothing else has come from this sensor and settings api so far. I don't think there is a use-case yet. If this is relevant to somebody, speak up ;)

Example:

$ SoapySDRUtil --probe="driver=plutosdr"
...
----------------------------------------------------
-- Peripheral summary
----------------------------------------------------
  Channels: 1 Rx, 1 Tx
  Timestamps: NO
  Sensors: xadc_temp0, xadc_voltage0, xadc_voltage1, xadc_voltage2, xadc_voltage3, xadc_voltage4, xadc_voltage5, xadc_voltage6, xadc_voltage7, xadc_voltage8, adm1177_current0, adm1177_voltage0, ad9361-phy_temp0, ad9361-phy_voltage2
     * xadc_temp0: 42.079944 C
     * xadc_voltage0 (vccint): 1.018066 V
     * xadc_voltage1 (vccaux): 1.803223 V
     * xadc_voltage2 (vccbram): 1.007812 V
     * xadc_voltage3 (vccpint): 1.007080 V
     * xadc_voltage4 (vccpaux): 1.803223 V
     * xadc_voltage5 (vccoddr): 1.348389 V
     * xadc_voltage6 (vrefp): 1.248047 V
     * xadc_voltage7 (vrefn): -0.000732 V
     * xadc_voltage8: 0.903076 V
     * adm1177_current0: 0.424646 A
     * adm1177_voltage0: 4.902026 V
     * ad9361-phy_temp0: 25.439000 C
     * ad9361-phy_voltage2: 0.573565 V
...

[guruofquality]

It seems like a useful and complete feature to me. I'm not sure if most of those voltage regulator values are meaningful outside of board bring-up, but temperature is always nice to have.

[zuckschwerdt]

Yes, more diagnostics is always nice. I'll split out the sensors API for merge and keep the settings API here for further development.

[zuckschwerdt]

master is stable for tagging now. We'll keep this settings api change open until someone figures out what the interesting bits to toggle are.