linux-kernel - Re: [PATCH RFC] power: reset: restart-poweroff: convert to module

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Date: Wed, 21 Feb 2024 22:01:44 +0100
From: Sebastian Reichel <sebastian.reichel@...labora.com>
To: "A. Sverdlin" <alexander.sverdlin@...mens.com>
Cc: linux-pm@...r.kernel.org, Andrew Lunn <andrew@...n.ch>, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH RFC] power: reset: restart-poweroff: convert to module

Hi,

On Wed, Feb 21, 2024 at 06:46:07PM +0100, A. Sverdlin wrote:
> From: Alexander Sverdlin <alexander.sverdlin@...mens.com>
> 
> The necessity of having a fake platform device for a generic, platform
> independent functionality is not obvious.
> Some platforms requre device tree modification for this, some would require
> ACPI tables modification, while functionality may be useful even to
> end-users without required expertise. Convert the platform driver to
> a simple module.
> 
> Signed-off-by: Alexander Sverdlin <alexander.sverdlin@...mens.com>
> ---
> This RFC is merely to understand if this approach would be accepted.
> Converting to "tristate" could follow or preceed this patch.

1. You cannot easily make this tristate, because of machine_restart().
2. This is already using module_platform_driver(), so this has
   nothing to do with making it a module like the subject suggests.
3. This no longer applies, since the driver is now properly using
   devm_register_sys_off_handler instead of pm_power_off.
4. It's intentional, that a device needs to be described. This is
   _not_ meant as a general purpose poweroff driver. It's intended
   to be used with bootloader support, which keeps the system off
   as described in the comment at the start of the file.

So: NAK

-- Sebastian

> diff --git a/drivers/power/reset/restart-poweroff.c b/drivers/power/reset/restart-poweroff.c
> index 28f1822db1626..e1d94109f6823 100644
> --- a/drivers/power/reset/restart-poweroff.c
> +++ b/drivers/power/reset/restart-poweroff.c
> @@ -20,7 +20,7 @@ static void restart_poweroff_do_poweroff(void)
>  	machine_restart(NULL);
>  }
>  
> -static int restart_poweroff_probe(struct platform_device *pdev)
> +static int __init restart_poweroff_init(void)
>  {
>  	/* If a pm_power_off function has already been added, leave it alone */
>  	if (pm_power_off != NULL) {
> @@ -33,12 +33,10 @@ static int restart_poweroff_probe(struct platform_device *pdev)
>  	return 0;
>  }
>  
> -static int restart_poweroff_remove(struct platform_device *pdev)
> +static void __exit restart_poweroff_exit(void)
>  {
>  	if (pm_power_off == &restart_poweroff_do_poweroff)
>  		pm_power_off = NULL;
> -
> -	return 0;
>  }
>  
>  static const struct of_device_id of_restart_poweroff_match[] = {
> @@ -47,15 +45,8 @@ static const struct of_device_id of_restart_poweroff_match[] = {
>  };
>  MODULE_DEVICE_TABLE(of, of_restart_poweroff_match);
>  
> -static struct platform_driver restart_poweroff_driver = {
> -	.probe = restart_poweroff_probe,
> -	.remove = restart_poweroff_remove,
> -	.driver = {
> -		.name = "poweroff-restart",
> -		.of_match_table = of_restart_poweroff_match,
> -	},
> -};
> -module_platform_driver(restart_poweroff_driver);
> +module_init(restart_poweroff_init);
> +module_exit(restart_poweroff_exit);
>  
>  MODULE_AUTHOR("Andrew Lunn <andrew@...n.ch");
>  MODULE_DESCRIPTION("restart poweroff driver");
> -- 
> 2.43.0
> 

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