linux-kernel - Re: [PATCH v9 20/22] ACPI: platform

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Message-ID: <e1653608-4073-3f2a-c8c9-9718320d071a@linux.intel.com>
Date: Thu, 5 Dec 2024 16:27:03 +0200 (EET)
From: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
To: Mario Limonciello <mario.limonciello@....com>
cc: Hans de Goede <hdegoede@...hat.com>, 
    "Rafael J . Wysocki" <rafael@...nel.org>, Len Brown <lenb@...nel.org>, 
    Maximilian Luz <luzmaximilian@...il.com>, Lee Chun-Yi <jlee@...e.com>, 
    Shyam Sundar S K <Shyam-sundar.S-k@....com>, 
    Corentin Chary <corentin.chary@...il.com>, 
    "Luke D . Jones" <luke@...nes.dev>, Ike Panhc <ike.pan@...onical.com>, 
    Henrique de Moraes Holschuh <hmh@....eng.br>, 
    Alexis Belmonte <alexbelm48@...il.com>, 
    Uwe Kleine-König <u.kleine-koenig@...gutronix.de>, 
    Ai Chao <aichao@...inos.cn>, Gergo Koteles <soyer@....hu>, 
    open list <linux-kernel@...r.kernel.org>, 
    "open list:ACPI" <linux-acpi@...r.kernel.org>, 
    "open list:MICROSOFT SURFACE PLATFORM PROFILE DRIVER" <platform-driver-x86@...r.kernel.org>, 
    "open list:THINKPAD ACPI EXTRAS DRIVER" <ibm-acpi-devel@...ts.sourceforge.net>, 
    Mark Pearson <mpearson-lenovo@...ebb.ca>, 
    Matthew Schwartz <matthew.schwartz@...ux.dev>, Armin Wolf <W_Armin@....de>
Subject: Re: [PATCH v9 20/22] ACPI: platform_profile: Allow multiple
 handlers

On Sun, 1 Dec 2024, Mario Limonciello wrote:

> Multiple drivers may attempt to register platform profile handlers,
> but only one may be registered and the behavior is non-deterministic
> for which one wins.  It's mostly controlled by probing order.
> 
> This can be problematic if one driver changes CPU settings and another
> driver notifies the EC for changing fan curves.
> 
> Modify the ACPI platform profile handler to let multiple drivers
> register platform profile handlers and abstract this detail from userspace.
> 
> To avoid undefined behaviors only offer profiles that are commonly
> advertised across multiple handlers.
> 
> If any problems occur when changing profiles for any driver, then the
> drivers that were already changed remain changed and the legacy sysfs
> handler will report 'custom'.
> 
> Tested-by: Mark Pearson <mpearson-lenovo@...ebb.ca>
> Tested-by: Matthew Schwartz <matthew.schwartz@...ux.dev>
> Reviewed-by: Mark Pearson <mpearson-lenovo@...ebb.ca>
> Reviewed-by: Armin Wolf <W_Armin@....de>
> Signed-off-by: Mario Limonciello <mario.limonciello@....com>
> ---
>  drivers/acpi/platform_profile.c | 11 -----------
>  1 file changed, 11 deletions(-)
> 
> diff --git a/drivers/acpi/platform_profile.c b/drivers/acpi/platform_profile.c
> index 289b5d43638ae..2e38aa410b3ad 100644
> --- a/drivers/acpi/platform_profile.c
> +++ b/drivers/acpi/platform_profile.c
> @@ -10,7 +10,6 @@
>  #include <linux/platform_profile.h>
>  #include <linux/sysfs.h>
>  
> -static struct platform_profile_handler *cur_profile;
>  static DEFINE_MUTEX(profile_lock);
>  
>  static const char * const profile_names[] = {
> @@ -399,8 +398,6 @@ static const struct attribute_group platform_profile_group = {
>  
>  void platform_profile_notify(struct platform_profile_handler *pprof)
>  {
> -	if (!cur_profile)
> -		return;
>  	scoped_cond_guard(mutex_intr, return, &profile_lock) {
>  		_notify_class_profile(pprof->class_dev, NULL);
>  	}
> @@ -463,9 +460,6 @@ int platform_profile_register(struct platform_profile_handler *pprof)
>  	}
>  
>  	guard(mutex)(&profile_lock);
> -	/* We can only have one active profile */
> -	if (cur_profile)
> -		return -EEXIST;
>  
>  	/* create class interface for individual handler */
>  	pprof->minor = ida_alloc(&platform_profile_ida, GFP_KERNEL);
> @@ -481,8 +475,6 @@ int platform_profile_register(struct platform_profile_handler *pprof)
>  
>  	sysfs_notify(acpi_kobj, NULL, "platform_profile");
>  
> -	cur_profile = pprof;
> -
>  	err = sysfs_update_group(acpi_kobj, &platform_profile_group);
>  	if (err)
>  		goto cleanup_cur;
> @@ -490,7 +482,6 @@ int platform_profile_register(struct platform_profile_handler *pprof)
>  	return 0;
>  
>  cleanup_cur:
> -	cur_profile = NULL;
>  	device_unregister(pprof->class_dev);
>  
>  cleanup_ida:
> @@ -505,8 +496,6 @@ int platform_profile_remove(struct platform_profile_handler *pprof)
>  	int id;
>  	guard(mutex)(&profile_lock);
>  
> -	cur_profile = NULL;
> -
>  	id = pprof->minor;
>  	device_unregister(pprof->class_dev);
>  	ida_free(&platform_profile_ida, id);
> 

Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>

-- 
 i.