Print all detected features when VF=1

[qmonnet]

Kernel file tools/build/Makefile.feature has

ifeq ($(VF),1)
  feature_display := 1
  feature_verbose := 1
endif

causing all features to be displayed:

$ VF=1 make

Auto-detecting system features:
...                         clang-bpf-co-re: [ on  ]
...                                    llvm: [ on  ]
...                                  libcap: [ on  ]
...                                  libbfd: [ on  ]
...                          libbfd-liberty: [ on  ]
...                        libbfd-liberty-z: [ on  ]
...                  disassembler-four-args: [ on  ]
...                disassembler-init-styled: [ on  ]
...                             libelf-zstd: [ on  ]

It could be useful for debugging features detection to have the same in this repository. We already have V=1, which prints the details of the detection, but this list is more succinct. On the other hand, it's also used in the kernel repo to force displaying the values when they would otherwise be skipped:

# The $(feature_display) controls the default detection message
# output. It's set if:
# - detected features differes from stored features from
#   last build (in $(FEATURE_DUMP_FILENAME) file)
# - one of the $(FEATURE_DISPLAY) is not detected
# - VF is enabled

but we don't have this issue in the GitHub repo, given that we don't dump features to a file and always print those in FEATURE_DISPLAY. Still, supporting VF=1 could be nice.

[Shankari02]

Hello @qmonnet, I want to improve this process and resolve the issue. Should I generate the patch and send it to the mailing list before creating the PR?

[qmonnet]

Hi, thanks for looking into this!

Usually the patches should go to the mailing list (and then they're automatically sync-ed with this repo), but this Issue is a particular case: We're trying to make the version from the GitHub repo behave more like the one from the kernel repo. It means that there's no change to do on kernel side, only in this repository. So we just need a PR against this repo.

[Shankari02]

Hi, thanks for looking into this!

Usually the patches should go to the mailing list (and then they're automatically sync-ed with this repo), but this Issue is a particular case: We're trying to make the version from the GitHub repo behave more like the one from the kernel repo. It means that there's no change to do on kernel side, only in this repository. So we just need a PR against this repo.

Thanks for clarifying! I'll generate a PR for this. Please assign me this issue.

[Shankari02]

Hi @qmonnet, I have made the required changes in Makefile.feature to display the features as required.

shankari@shankari-IdeaPad:~/bpftool/src$ VF=1 make
...                        libbfd: [ on  ]
...                libbfd-liberty: [ OFF ]
...              libbfd-liberty-z: [ OFF ]
...               clang-bpf-co-re: [ on  ]
...                          llvm: [ on  ]
...                        libcap: [ on  ]
...        disassembler-four-args: [ on  ]
...      disassembler-init-styled: [ on  ]
...                   libelf-zstd: [ OFF ]
make: Nothing to be done for 'all'.

This is the output I have got. Please verify this and let me know if it seems fine, then, I'll generate a PR.

[qmonnet]

Yes, this looks OK to me 👍

[Shankari02]

I have generated the PR - #186.
Please let me know if there are any changes to be made. Thanks!