[PATCH i-g-t v3] lib/igt_kmod: Allow to load kunit from alias

[Mauro Carvalho Chehab]

On Fri,  8 Mar 2024 11:31:49 -0800
Lucas De Marchi <lucas.demarchi at intel.com> wrote:

> Instead of only allowing to load the from the module name, also allow it
> from alias by using kmod_module_new_from_lookup(). With that a user can
> have their on aliases and the kernel can also export a compat alias for
> future module renames.
> 
> There was a bug in libkmod <= 29 that would make
> kmod_module_new_from_lookup() return prematurely after a failed alias
> lookup when we don't have a modules.alias file in the modules dir. So
> add a workaround to check for -ENOSYS return code too. It should still
> be compatible with what we are doing here.
> 
> v2: Fallback to kmod_module_new_from_name() since the kmod ctx is also
>     used on builder machines to determine the test lists.
> v3: Add workaround to bug in libkmod
> 
> Signed-off-by: Lucas De Marchi <lucas.demarchi at intel.com>
> ---
>  lib/igt_kmod.c | 21 +++++++++++++++++++--
>  1 file changed, 19 insertions(+), 2 deletions(-)
> 
> diff --git a/lib/igt_kmod.c b/lib/igt_kmod.c
> index cc242838f..d581f9073 100644
> --- a/lib/igt_kmod.c
> +++ b/lib/igt_kmod.c
> @@ -1443,6 +1443,7 @@ void igt_kunit(const char *module_name, const char *suite, const char *opts)
>  int igt_ktest_init(struct igt_ktest *tst,
>  		   const char *module_name)
>  {
> +	struct kmod_list *l = NULL;
>  	int err;
>  
>  	memset(tst, 0, sizeof(*tst));
> @@ -1453,9 +1454,25 @@ int igt_ktest_init(struct igt_ktest *tst,
>  
>  	tst->kmsg = -1;
>  
> -	err = kmod_module_new_from_name(kmod_ctx(), module_name, &tst->kmod);
> -	if (err)
> +	err = kmod_module_new_from_lookup(kmod_ctx(), module_name, &l);
> +
> +	/*
> +	 * Check for -ENOSYS to workaround bug in kmod_module_new_from_lookup()
> +	 * from libkmod <= 29
> +	 */

Hmm... if the bug is not present anymore on more modern libkmod versions,
shouldn't the code be verifying the libkmod version?

Also, better to add a link to the bug inside the comment, in case the
workaround would require maintenance in the future.

With that, feel free to add my:

Reviewed-by: Mauro Carvalho Chehab <mchehab at kernel.org>

> +	if (err < 0 && err != -ENOSYS) {
>  		return err;
> +	}
> +
> +	/*
> +	 * Lookup may not resolve to a module when used to just list subtests,
> +	 * where module is not available. Fallback to _new_from_name().
> +	 */
> +	if (!l)
> +		return kmod_module_new_from_name(kmod_ctx(), module_name, &tst->kmod);
> +
> +	tst->kmod = kmod_module_get_module(l);
> +	kmod_module_unref_list(l);
>  
>  	return 0;
>  }