Re: [PATCH v3 0/6] rtla: Migrate to libsubcmd for command line option parsing

[Wander Lairson Costa <wander@redhat.com>]

On Thu, May 28, 2026 at 12:32:48PM +0200, Tomas Glozar wrote:
> [ CC to linux-perf-users for the libsubcmd code changes ]
> 
> rtla currently uses its own implementation that uses getopt_long() to
> parse command-line arguments.
> 
> Migrate rtla to use libsubcmd for command line argument parsing,
> similarly to what is already done by other tools like perf, bpftool,
> and objtool. Among other benefits, this allows help messages to be
> generated automatically rather than having to be typed out manually
> for each tool.
> 
> libsubcmd is extended with a flag to parse optarg from separate
> argument if a new flag is turned on. Without the flag, the old behavior
> is preserved. That keeps the parsing working for tools that use
> positional arguments, and allows RTLA to keep its flexible syntax for -C
> and -t options and their long variants, --cgroup and --trace-output.
> Another flag is added to disable automatic definition of --no-xy for
> every option --xy and vice versa, which overlaps for RTLA's --irq and
> --thread options.
> 
> The new implementation is moved into a separate file, cli.c, together
> with a tiny header counterpart, cli.h. This helps separate the parsing
> logic, which has little in common with the rest of RTLA, in a separate
> module. Another new file, cli_p.h, is used as a private header to contain
> macros and static function declarations that are also used by unit tests
> next to cli.c, but should not be imported from elsewhere.
> 
> Macros to generate struct option array fields for libsubcmd's
> parse_args() are used to preserve the consolidation of argument parsing
> code across different RTLA tools. Kernel and user threads are, as
> an exception, treated as common, although they are currently implemented
> for timerlat only, in line with earlier consolidation changes.
> 
> The test suite is expanded to include two levels of unit tests, one testing
> the already existing tool_parse_args() functions, one tests option callbacks,
> which are a new level of the CLI parser added in this patchset. This helps
> to verify that no regressions are caused by this refactoring.
> 
> I expect more improvements to the code being possible in the future,
> like creating macros for option groups to further deduplicate the code,
> reducing the amount of extra code in the _parse_args() functions, or
> implementing support for unsetting options (which is currently only
> supported for those that do not use a custom callback).
> 
> Base commit:
> - https://git.kernel.org/pub/scm/linux/kernel/git/tglozar/linux.git/commit/?h=rtla-for-next&id=f03a59f949176ce4312cb466245d1243aaf40389
> 
> Dependencies:
> - https://lore.kernel.org/linux-trace-kernel/20260423130558.882022-1-tglozar@redhat.com/T/
> - https://lore.kernel.org/linux-trace-kernel/20260424140244.958495-1-tglozar@redhat.com/
> - https://lore.kernel.org/linux-trace-kernel/20260414185223.65353-1-costa.shul@redhat.com/
> (apply in reverse order, alternatively, use base commit above)
> 
> v3 changes (all in cover letter or first commit):
> - Add FORCE to all targets that feature a make subcommand to ensure changes
> in the dependency will trigger rebuild correctly.
> - Convert all dependencies on directory targets LIBSUBCMD_OUTPUT and
> LIB_OUTPUT into order-only prerequisites to prevent modifications of
> the directory content triggering rebuild of targets inside it.
> - Properly mention depedencies of the patchset in the cover letter, as well
> as the base commit.
> 
> v2: https://lore.kernel.org/linux-trace-kernel/20260521141833.2353025-1-tglozar@redhat.com/T/
> 

Oops. I mistakenly added the reviewed-by tag to the v2 patch series.

Reviewed-by: Wander Lairson Costa <wander@redhat.com>