[sflow]: Unblocked psample_*() function calls related to BRCM specific procfs for sflow feature's working in ESW platforms

[hari-selvam]

Fixed sflow feature code breakage in BRCM ESW platform.

*Replaced BRCM SDK's psample support flag(PSAMPLE_SUPPORT) with linux kernel psample module support config flag(CONFIG_PSAMPLE) in saibcm-modules.
*Replaced BUILD_PSAMPLE conditioanl check with CONFIG_PSAMPLE to build psample callback library(psample-cb.o), only if psample config is enabled in linux kernel.
*Cleaned up PSAMPLE_SUPPORT related commented code.

Signed-off-by: haris@celestica.com

Why I did it

SFLOW configuration(config sflow enable) causes swss docker to exit in Broadcom Td3-X2 family chipset platform. Reason is as part of the sflow configuration, Broadcom tries to open the file /proc/bcm/knet_cb/psample/rate and it got failed since the file doesn't exists. psample-cb.o object file is responsible for loading '/proc/bcm/knet-cb/psample/rate' file. And this object file is not included due to BUILD_PSAMPLE=1 flag is removed in the recent commit.

How I did it

Unblocked psample_*() function calls in BRCM ESW platforms for proper functionality of sflow feature.
*Replaced BRCM SDK's psample support flag(PSAMPLE_SUPPORT) with linux kernel psample module support config flag(CONFIG_PSAMPLE) in saibcm-modules.
*Replaced BUILD_PSAMPLE conditioanl check with CONFIG_PSAMPLE to build psample callback library(psample-cb.o), only if psample config is enabled in linux kernel.
*Cleaned up PSAMPLE_SUPPORT related commented code.

How to verify it

1. Check psample module is insmoded by default by using 'lsmod | grep psample' command. pass
2. Check required procfs such as (debug, map, rate, size, stats) are created under /proc/bcm/knet-cb/psample/ folder. pass
3. Enable sflow feature by using 'config feature state sflow enabled' command. pass
4. Check sflow docker is instantiated by using 'docker ps' command. pass
5. Check sflow config(config sflow enable) doesnt stop swss docker. pass
6. Check COUNTER and FLOW samples are being received at the configured collector interface. pass
7. Change sflow attributes(global and interface specific) and verify the config changes are affecting samples count or not. pass
8. Check sflow functionality after cold reboot. pass

Which release branch to backport (provide reason below if selected)

• 201811
• 201911
• 202006
• 202012
• 202106
• 202111
• 202205

Description for the changelog

Replaced BRCM SDK psample support flag with kernel psample config flag to unblock the creation of BRCM specific procfs for sflow feature's working in ESW platforms. It fixes Issue#12810

Ensure to add label/tag for the feature raised. example - PR#2174 under sonic-utilities repo. where, Generic Config and Update feature has been labelled as GCU.

[saibcm-modules][sflow]

Link to config_db schema for YANG module changes

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

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: hari-selvam (0cbd152)

[lguohan]

@adyeung , can you find someone review this pr?

[adyeung]

@michaelli10 already engaged with hari-selvam in the other thread

@michaelli10 pls help review the PR

[michaelli10]

Discussed changes previously with Hari and tested with and and without CONFIG_PSAMPLE

[mssonicbld]

Cherry-pick PR to 202205: #13001

[mssonicbld]

Cherry-pick PR to 202211: #13691