linux-kernel - Re: [PATCH v4 18/20] ACPI: platform

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Message-ID: <220ed38a-14ab-44e5-a8bb-dd5eb2888239@amd.com>
Date: Wed, 6 Nov 2024 13:34:05 -0600
From: Mario Limonciello <mario.limonciello@....com>
To: Armin Wolf <W_Armin@....de>, 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>,
 "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>
Subject: Re: [PATCH v4 18/20] ACPI: platform_profile: Allow multiple handlers

On 11/6/2024 13:33, Armin Wolf wrote:
> Am 06.11.24 um 20:21 schrieb Armin Wolf:
> 
>> Am 05.11.24 um 16:33 schrieb Mario Limonciello:
>>
>>> 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.
>>
>> Reviewed-by: Armin Wolf <W_Armin@....de>
>>
> I just noticed that the following text might need to be removed:
> 
> "If any problems occur when changing profiles for any driver, then revert
>   back to the balanced profile, which is now required."

Good catch, thanks.

> 
> Thanks,
> Armin Wolf
> 
>>> Tested-by: Matthew Schwartz <matthew.schwartz@...ux.dev>
>>> Reviewed-by: Mark Pearson <mpearson-lenovo@...ebb.ca>
>>> Signed-off-by: Mario Limonciello <mario.limonciello@....com>
>>> ---
>>>   drivers/acpi/platform_profile.c | 12 ++----------
>>>   1 file changed, 2 insertions(+), 10 deletions(-)
>>>
>>> diff --git a/drivers/acpi/platform_profile.c
>>> b/drivers/acpi/platform_profile.c
>>> index 568485e285061..b9eb25f58a2a2 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[] = {
>>> @@ -368,8 +367,7 @@ static const struct attribute_group
>>> platform_profile_group = {
>>>
>>>   void platform_profile_notify(void)
>>>   {
>>> -    if (!cur_profile)
>>> -        return;
>>> +    guard(mutex)(&profile_lock);
>>>       if (!class_is_registered(&platform_profile_class))
>>>           return;
>>>       sysfs_notify(acpi_kobj, NULL, "platform_profile");
>>> @@ -428,9 +426,6 @@ 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;
>>>
>>>       if (!class_is_registered(&platform_profile_class)) {
>>>           /* class for individual handlers */
>>> @@ -451,9 +446,9 @@ int platform_profile_register(struct
>>> platform_profile_handler *pprof)
>>>       if (IS_ERR(pprof->class_dev))
>>>           return PTR_ERR(pprof->class_dev);
>>>       dev_set_drvdata(pprof->class_dev, pprof);
>>> +
>>>       sysfs_notify(acpi_kobj, NULL, "platform_profile");
>>>
>>> -    cur_profile = pprof;
>>>       return 0;
>>>
>>>   cleanup_class:
>>> @@ -467,13 +462,10 @@ int platform_profile_remove(struct
>>> platform_profile_handler *pprof)
>>>   {
>>>       guard(mutex)(&profile_lock);
>>>
>>> -    cur_profile = NULL;
>>> -
>>>       sysfs_notify(acpi_kobj, NULL, "platform_profile");
>>>
>>>       device_destroy(&platform_profile_class, MKDEV(0, pprof->minor));
>>>
>>> -    cur_profile = NULL;
>>>       return 0;
>>>   }
>>>   EXPORT_SYMBOL_GPL(platform_profile_remove);
>>