[PATCH v5 2/4] kernel: param: initialize module_kset in a pure_initcall

[Petr Pavlu]

On 5/18/26 12:19 PM, Shashank Balaji wrote:
> Commit "driver core: platform: set mod_name in driver registration" will set
> struct device_driver's mod_name member for platform driver registration. For a
> driver to be registered with its mod_name set, module_kset needs to be
> initialized, which currently happens in a subsys_initcall in param_sysfs_init().
> The tegra cbb drivers register themselves before module_kset init, in a
> core_initcall. This works currently because lookup_or_create_module_kobject(),
> which dereferences module_kset via kset_find_obj(), is not called if mod_name
> is not set, which is the case now.
> 
> So in preparation for the commit "driver core: platform: set mod_name in driver registration",
> move module_kset init to pure_initcall level, ensuring it happens before tegra
> cbb driver registration.
> 
> Suggested-by: Gary Guo <gary at garyguo.net>
> Co-developed-by: Rahul Bukte <rahul.bukte at sony.com>
> Signed-off-by: Rahul Bukte <rahul.bukte at sony.com>
> Signed-off-by: Shashank Balaji <shashank.mahadasyam at sony.com>
> ---
> Patch 4 depends on this patch
> ---
>  kernel/params.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/params.c b/kernel/params.c
> index 74d620bc2521..ac088d4b09a9 100644
> --- a/kernel/params.c
> +++ b/kernel/params.c
> @@ -957,7 +957,7 @@ static int __init param_sysfs_init(void)
>  
>  	return 0;
>  }
> -subsys_initcall(param_sysfs_init);
> +pure_initcall(param_sysfs_init);
>  
>  /*
>   * param_sysfs_builtin_init - add sysfs version and parameter
> 

The change looks ok to me functionality-wise. Sysfs is initialized
earlier in do_basic_setup() and other code, such as classes_init(),
calls kset_create_and_add() similarly early.

One minor issue is that pure_initcall() was originally intended for
static variable initialization. The file include/linux/init.h says:

| /*
|  * A "pure" initcall has no dependencies on anything else, and purely
|  * initializes variables that couldn't be statically initialized.
|  *
|  * This only exists for built-in code, not for modules.
|  * Keep main.c:initcall_level_names[] in sync.
|  */
| #define pure_initcall(fn)		__define_initcall(fn, 0)

The patch stretches the intended use of pure_initcall() somewhat in this
regard. However, other code already appears to do the same, so I guess
this is ok.

Additionally, I think it would be good to update the comment preceding
param_sysfs_init(). It currently says:

| /*
|  * param_sysfs_init - create "module" kset
|  *
|  * This must be done before the initramfs is unpacked and
|  * request_module() thus becomes possible, because otherwise the
|  * module load would fail in mod_sysfs_init.
|  */

I suggest changing it to something like follows:

This must be done before any driver registration so that when a driver comes
from a built-in module, the driver core can add the module under /sys/module
and create the associated driver symlinks.

-- 
Thanks,
Petr