linux-kernel - Re: [PATCH v3 21/22] ACPI: platform

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Message-Id: <22e1712a-d5ca-411d-b75c-2cb2288ecbf7@app.fastmail.com>
Date: Fri, 01 Nov 2024 22:15:58 -0400
From: "Mark Pearson" <mpearson-lenovo@...ebb.ca>
To: "Limonciello, Mario" <mario.limonciello@....com>,
 "Hans de Goede" <hdegoede@...hat.com>,
 Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
Cc: "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>,
 "linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
 "platform-driver-x86@...r.kernel.org" <platform-driver-x86@...r.kernel.org>,
 "open list:THINKPAD ACPI EXTRAS DRIVER" <ibm-acpi-devel@...ts.sourceforge.net>,
 "Matthew Schwartz" <matthew.schwartz@...ux.dev>
Subject: Re: [PATCH v3 21/22] ACPI: platform_profile: Allow multiple handlers

On Thu, Oct 31, 2024, at 12:09 AM, 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 revert
> back to the balanced profile, which is now required.
>
> Tested-by: Matthew Schwartz <matthew.schwartz@...ux.dev>
> Signed-off-by: Mario Limonciello <mario.limonciello@....com>
> ---
>  drivers/acpi/platform_profile.c | 10 ++--------
>  1 file changed, 2 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/acpi/platform_profile.c b/drivers/acpi/platform_profile.c
> index 1cc8182930dde..a845524a248b9 100644
> --- a/drivers/acpi/platform_profile.c
> +++ b/drivers/acpi/platform_profile.c
> @@ -9,7 +9,6 @@
>  #include <linux/platform_profile.h>
>  #include <linux/sysfs.h>
> 
> -static struct platform_profile_handler *cur_profile;
>  static LIST_HEAD(platform_profile_handler_list);
>  static DEFINE_MUTEX(profile_lock);
> 
> @@ -212,7 +211,8 @@ static const struct attribute_group 
> platform_profile_group = {
> 
>  void platform_profile_notify(void)
>  {
> -	if (!cur_profile)
> +	guard(mutex)(&profile_lock);
> +	if (!platform_profile_is_registered())
>  		return;
>  	sysfs_notify(acpi_kobj, NULL, "platform_profile");
>  }
> @@ -280,9 +280,6 @@ 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;
> 
>  	registered = platform_profile_is_registered();
>  	if (!registered) {
> @@ -313,7 +310,6 @@ int platform_profile_register(struct 
> platform_profile_handler *pprof)
>  	list_add_tail(&pprof->list, &platform_profile_handler_list);
>  	sysfs_notify(acpi_kobj, NULL, "platform_profile");
> 
> -	cur_profile = pprof;
>  	return 0;
> 
>  cleanup_device:
> @@ -336,8 +332,6 @@ int platform_profile_remove(struct 
> platform_profile_handler *pprof)
> 
>  	list_del(&pprof->list);
> 
> -	cur_profile = NULL;
> -
>  	sysfs_notify(acpi_kobj, NULL, "platform_profile");
> 
>  	sysfs_remove_group(&pprof->class_dev->kobj, &platform_profile_group);
> -- 
> 2.43.0

Looks good to me
Reviewed-by: Mark Pearson <mpearson-lenovo@...ebb.ca>

Mark