DellEMC S6000 fancontrol support

[paavaanan]

- What I did

• Added fancontrol support for DellEMC S6000 platform

- How I did it

• Implemented fancontrol service to monitor S6000 fans and adjust fan speed w.r.t temperature.
• fancontrol.service starts the fancontrol script at startup.
• This script takes the average temperature by reading three sensors and configure FANS to appropritate RPM against the temperature.
• When the temperature is adjusted script will log in syslog for future reference.
• Also, script checks for faulty fans and report the status in syslog.

- How to verify it

• verify fancontrol status by issuing "systemctl status fancontrol" command
• Check syslog for fancontrol like below messages.

Jan  3 07:34:55.716486 sonic NOTICE root: Adjusted FAN Speed to 7000 RPM against 29 Temperature
Jan  3 07:34:55.777522 sonic NOTICE root: FanTray3 Fans are Faulty.. 240 240. Please check.

- Description for the changelog

- A picture of a cute animal (not mandatory but encouraged)

[sujinmkang]

retest this please

[lguohan]

We need this for master. I am not sure we need this in 201811 branch.

[jleveque]

Curious: Are you not able to simply provide a config file for the existing fancontrol daemon (example: https://github.com/Azure/sonic-buildimage/blob/master/device/arista/x86_64-arista_7050_qx32/fancontrol)?

[paavaanan]

@jleveque - Linux fancontrol script/config files is designed to work only with PWM values. But max6620 (FAN) Linux driver support fancntrol only through RPM values. PWM values are read-only. No read-write support is availlable via PWM in current driver. So, config file and associated scripts are not usable for this case.

[paavaanan]

Raised a new Pr for master in #4048