in_thermal: support hwmon

[nokute78]

This patch is to support to read a temperature from hwmon subsystem. See also #7955
https://www.kernel.org/doc/Documentation/hwmon/sysfs-interface

in_thermal tries to read a temperature from /sys/class/thermal first.
If in_thermal can't read it, in_thermal tries to read /sys/class/hwmon.

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Testing
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• [N/A] Example configuration file for the change
• Debug log output from testing the change

• Attached Valgrind output that shows no leaks or memory corruption was found

If this is a change to packaging of containers or native binaries then please confirm it works for all targets.

• [N/A] Run local packaging test showing all targets (including any new ones) build.
• [N/A] Set ok-package-test label to test for all targets (requires maintainer to do).

Documentation

• [N/A] Documentation required for this feature

Backporting

• [N/A] Backport to latest stable release.

Debug/Valgrind output

Note: I modified source not to read /sys/class/thermal to enforce reading from /sys/class/hwmon.

$ valgrind --leak-check=full bin/fluent-bit -i thermal -o stdout
==25894== Memcheck, a memory error detector
==25894== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al.
==25894== Using Valgrind-3.18.1 and LibVEX; rerun with -h for copyright info
==25894== Command: bin/fluent-bit -i thermal -o stdout
==25894== 
Fluent Bit v2.2.0
* Copyright (C) 2015-2022 The Fluent Bit Authors
* Fluent Bit is a CNCF sub-project under the umbrella of Fluentd
* https://fluentbit.io

[2023/10/08 10:22:15] [ info] [fluent bit] version=2.2.0, commit=cfca7ca8ac, pid=25894
[2023/10/08 10:22:15] [ info] [storage] ver=1.5.1, type=memory, sync=normal, checksum=off, max_chunks_up=128
[2023/10/08 10:22:15] [ info] [cmetrics] version=0.6.3
[2023/10/08 10:22:15] [ info] [ctraces ] version=0.3.1
[2023/10/08 10:22:15] [ info] [input:thermal:thermal.0] initializing
[2023/10/08 10:22:15] [ info] [input:thermal:thermal.0] storage_strategy='memory' (memory only)
[2023/10/08 10:22:15] [ info] [output:stdout:stdout.0] worker #0 started
[2023/10/08 10:22:15] [ info] [sp] stream processor started
==25894== Warning: client switching stacks?  SP change: 0x6f68ba0 --> 0x54c5df0
==25894==          to suppress, use: --max-stackframe=27930032 or greater
==25894== Warning: client switching stacks?  SP change: 0x54c5cf0 --> 0x6f68ba0
==25894==          to suppress, use: --max-stackframe=27930288 or greater
==25894== Warning: client switching stacks?  SP change: 0x6f68ba0 --> 0x54c5cf0
==25894==          to suppress, use: --max-stackframe=27930288 or greater
==25894==          further instances of this message will not be shown.
[0] thermal.0: [[1696728135.681488126, {}], {"name"=>"hwmon6_temp1_input", "type"=>"npu_thermal", "temp"=>39.769000}]
[1] thermal.0: [[1696728135.699476030, {}], {"name"=>"hwmon4_temp1_input", "type"=>"center_thermal", "temp"=>39.769000}]
[2] thermal.0: [[1696728135.699658327, {}], {"name"=>"hwmon2_temp1_input", "type"=>"bigcore1_thermal", "temp"=>40.692000}]
[3] thermal.0: [[1696728135.699734454, {}], {"name"=>"hwmon0_temp1_input", "type"=>"soc_thermal", "temp"=>40.692000}]
[4] thermal.0: [[1696728135.699821956, {}], {"name"=>"hwmon5_temp1_input", "type"=>"gpu_thermal", "temp"=>39.769000}]
[5] thermal.0: [[1696728135.699894292, {}], {"name"=>"hwmon3_temp1_input", "type"=>"littlecore_thermal", "temp"=>39.769000}]
[6] thermal.0: [[1696728135.699965169, {}], {"name"=>"hwmon1_temp1_input", "type"=>"bigcore0_thermal", "temp"=>39.769000}]
^C[2023/10/08 10:22:17] [engine] caught signal (SIGINT)
[2023/10/08 10:22:17] [ warn] [engine] service will shutdown in max 5 seconds
[0] thermal.0: [[1696728136.677026745, {}], {"name"=>"hwmon6_temp1_input", "type"=>"npu_thermal", "temp"=>39.769000}]
[1] thermal.0: [[1696728136.677146040, {}], {"name"=>"hwmon4_temp1_input", "type"=>"center_thermal", "temp"=>39.769000}]
[2] thermal.0: [[1696728136.677217500, {}], {"name"=>"hwmon2_temp1_input", "type"=>"bigcore1_thermal", "temp"=>39.769000}]
[3] thermal.0: [[1696728136.677286336, {}], {"name"=>"hwmon0_temp1_input", "type"=>"soc_thermal", "temp"=>39.769000}]
[4] thermal.0: [[1696728136.677356046, {}], {"name"=>"hwmon5_temp1_input", "type"=>"gpu_thermal", "temp"=>38.846000}]
[5] thermal.0: [[1696728136.677429840, {}], {"name"=>"hwmon3_temp1_input", "type"=>"littlecore_thermal", "temp"=>39.769000}]
[6] thermal.0: [[1696728136.677496925, {}], {"name"=>"hwmon1_temp1_input", "type"=>"bigcore0_thermal", "temp"=>39.769000}]
[2023/10/08 10:22:17] [ info] [input] pausing thermal.0
[2023/10/08 10:22:17] [ info] [engine] service has stopped (0 pending tasks)
[2023/10/08 10:22:17] [ info] [input] pausing thermal.0
[2023/10/08 10:22:17] [ info] [output:stdout:stdout.0] thread worker #0 stopping...
[2023/10/08 10:22:17] [ info] [output:stdout:stdout.0] thread worker #0 stopped
==25894== 
==25894== HEAP SUMMARY:
==25894==     in use at exit: 0 bytes in 0 blocks
==25894==   total heap usage: 1,926 allocs, 1,926 frees, 1,800,381 bytes allocated
==25894== 
==25894== All heap blocks were freed -- no leaks are possible
==25894== 
==25894== For lists of detected and suppressed errors, rerun with: -s
==25894== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)

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Fluent Bit is licensed under Apache 2.0, by submitting this pull request I understand that this code will be released under the terms of that license.

[mmguero]

I tested this patch (I'm the reporter of #7955) and can confirm it did work for me and resolve the reported issue.

[mmguero]

Any chance we can get this merged soon-ish?

[nokute78]

@edsiper @leonardo-albertovich Could you review this ?