linux-kernel - Re: [PATCH] scripts/bpf_doc: add __main_

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Date:   Fri, 1 Dec 2023 16:46:22 +0100
From:   Daniel Borkmann <daniel@...earbox.net>
To:     Hu Haowen <2023002089@...k.tyut.edu.cn>, song@...nel.org,
        yonghong.song@...ux.dev, john.fastabend@...il.com,
        kpsingh@...nel.org, sdf@...gle.com, haoluo@...gle.com,
        jolsa@...nel.org, martin.lau@...ux.dev
Cc:     ast@...nel.org, andrii@...nel.org, bpf@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] scripts/bpf_doc: add __main__ judgement before main code

Hi Hu,

On 11/30/23 3:57 PM, Hu Haowen wrote:
> When doing Python programming it is a nice convention to insert the if
> statement `if __name__ == "__main__":` before any main code that does
> actual functionalities to ensure the code will be executed only as a
> script rather than as an imported module.  Hence attach the missing
> judgement to bpf_doc.py.
> 
> Signed-off-by: Hu Haowen <2023002089@...k.tyut.edu.cn>

Thanks for the patch. What's the concrete value of this one? Do you plan
to distribute the bpf_docs.py outside of the kernel tree? If it's not
needed feels somewhat too much churn/marginal value.

>   scripts/bpf_doc.py | 81 +++++++++++++++++++++++-----------------------
>   1 file changed, 41 insertions(+), 40 deletions(-)
> 
> diff --git a/scripts/bpf_doc.py b/scripts/bpf_doc.py
> index 61b7dddedc46..af2a87d97832 100755
> --- a/scripts/bpf_doc.py
> +++ b/scripts/bpf_doc.py
> @@ -851,43 +851,44 @@ class PrinterHelpers(Printer):
>   
>   ###############################################################################
>   
> -# If script is launched from scripts/ from kernel tree and can access
> -# ../include/uapi/linux/bpf.h, use it as a default name for the file to parse,
> -# otherwise the --filename argument will be required from the command line.
> -script = os.path.abspath(sys.argv[0])
> -linuxRoot = os.path.dirname(os.path.dirname(script))
> -bpfh = os.path.join(linuxRoot, 'include/uapi/linux/bpf.h')
> -
> -printers = {
> -        'helpers': PrinterHelpersRST,
> -        'syscall': PrinterSyscallRST,
> -}
> -
> -argParser = argparse.ArgumentParser(description="""
> -Parse eBPF header file and generate documentation for the eBPF API.
> -The RST-formatted output produced can be turned into a manual page with the
> -rst2man utility.
> -""")
> -argParser.add_argument('--header', action='store_true',
> -                       help='generate C header file')
> -if (os.path.isfile(bpfh)):
> -    argParser.add_argument('--filename', help='path to include/uapi/linux/bpf.h',
> -                           default=bpfh)
> -else:
> -    argParser.add_argument('--filename', help='path to include/uapi/linux/bpf.h')
> -argParser.add_argument('target', nargs='?', default='helpers',
> -                       choices=printers.keys(), help='eBPF API target')
> -args = argParser.parse_args()
> -
> -# Parse file.
> -headerParser = HeaderParser(args.filename)
> -headerParser.run()
> -
> -# Print formatted output to standard output.
> -if args.header:
> -    if args.target != 'helpers':
> -        raise NotImplementedError('Only helpers header generation is supported')
> -    printer = PrinterHelpers(headerParser)
> -else:
> -    printer = printers[args.target](headerParser)
> -printer.print_all()
> +if __name__ == "__main__":
> +    # If script is launched from scripts/ from kernel tree and can access
> +    # ../include/uapi/linux/bpf.h, use it as a default name for the file to parse,
> +    # otherwise the --filename argument will be required from the command line.
> +    script = os.path.abspath(sys.argv[0])
> +    linuxRoot = os.path.dirname(os.path.dirname(script))
> +    bpfh = os.path.join(linuxRoot, 'include/uapi/linux/bpf.h')
> +
> +    printers = {
> +            'helpers': PrinterHelpersRST,
> +            'syscall': PrinterSyscallRST,
> +    }
> +
> +    argParser = argparse.ArgumentParser(description="""
> +    Parse eBPF header file and generate documentation for the eBPF API.
> +    The RST-formatted output produced can be turned into a manual page with the
> +    rst2man utility.
> +    """)
> +    argParser.add_argument('--header', action='store_true',
> +                           help='generate C header file')
> +    if (os.path.isfile(bpfh)):
> +        argParser.add_argument('--filename', help='path to include/uapi/linux/bpf.h',
> +                               default=bpfh)
> +    else:
> +        argParser.add_argument('--filename', help='path to include/uapi/linux/bpf.h')
> +    argParser.add_argument('target', nargs='?', default='helpers',
> +                           choices=printers.keys(), help='eBPF API target')
> +    args = argParser.parse_args()
> +
> +    # Parse file.
> +    headerParser = HeaderParser(args.filename)
> +    headerParser.run()
> +
> +    # Print formatted output to standard output.
> +    if args.header:
> +        if args.target != 'helpers':
> +            raise NotImplementedError('Only helpers header generation is supported')
> +        printer = PrinterHelpers(headerParser)
> +    else:
> +        printer = printers[args.target](headerParser)
> +    printer.print_all()
>