linux-kernel - Re: [PATCH v5 11/20] ACPI: platform_profile: Add choices attribute for class interface

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Message-ID: <ba57628a-91d1-4e7c-8ebc-c5dc9db3d195@gmx.de>
Date: Fri, 8 Nov 2024 20:44:30 +0100
From: Armin Wolf <W_Armin@....de>
To: Mario Limonciello <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>,
 "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 v5 11/20] ACPI: platform_profile: Add choices attribute
 for class interface

Am 08.11.24 um 20:25 schrieb Mario Limonciello:

> On 11/8/2024 12:06, Armin Wolf wrote:
>> Am 07.11.24 um 23:09 schrieb Mario Limonciello:
>>
>>> On 11/7/2024 02:28, Armin Wolf wrote:
>>>> Am 07.11.24 um 07:02 schrieb Mario Limonciello:
>>>>
>>>>> The `choices` file will show all possible choices that a given
>>>>> platform
>>>>> profile handler can support.
>>>>>
>>>>> Tested-by: Mark Pearson <mpearson-lenovo@...ebb.ca>
>>>>> Signed-off-by: Mario Limonciello <mario.limonciello@....com>
>>>>> ---
>>>>> v5:
>>>>>   * Fix kdoc
>>>>>   * Add tag
>>>>>   * Fix whitespace
>>>>>   * Adjust mutex use
>>>>> ---
>>>>>   drivers/acpi/platform_profile.c | 65
>>>>> +++++++++++++++++++++++++++++++++
>>>>>   1 file changed, 65 insertions(+)
>>>>>
>>>>> diff --git a/drivers/acpi/platform_profile.c b/drivers/acpi/
>>>>> platform_profile.c
>>>>> index f605c2bd35c68..5e0bb91c5f451 100644
>>>>> --- a/drivers/acpi/platform_profile.c
>>>>> +++ b/drivers/acpi/platform_profile.c
>>>>> @@ -25,6 +25,46 @@ static_assert(ARRAY_SIZE(profile_names) ==
>>>>> PLATFORM_PROFILE_LAST);
>>>>>
>>>>>   static DEFINE_IDA(platform_profile_ida);
>>>>>
>>>>> +/**
>>>>> + * _commmon_choices_show - Show the available profile choices
>>>>> + * @choices: The available profile choices
>>>>> + * @buf: The buffer to write to
>>>>> + * Return: The number of bytes written
>>>>> + */
>>>>> +static ssize_t _commmon_choices_show(unsigned long choices, char
>>>>> *buf)
>>>>> +{
>>>>> +    int i, len = 0;
>>>>> +
>>>>> +    for_each_set_bit(i, &choices, PLATFORM_PROFILE_LAST) {
>>>>> +        if (len == 0)
>>>>> +            len += sysfs_emit_at(buf, len, "%s", profile_names[i]);
>>>>> +        else
>>>>> +            len += sysfs_emit_at(buf, len, " %s", profile_names[i]);
>>>>> +    }
>>>>> +    len += sysfs_emit_at(buf, len, "\n");
>>>>> +
>>>>> +    return len;
>>>>> +}
>>>>> +
>>>>> +/**
>>>>> + * _get_class_choices - Get the available profile choices for a
>>>>> class device
>>>>> + * @dev: The class device
>>>>> + * @choices: Pointer to return the available profile choices
>>>>> + * Return: The available profile choices
>>>>> + */
>>>>> +static int _get_class_choices(struct device *dev, unsigned long
>>>>> *choices)
>>>>> +{
>>>>> +    struct platform_profile_handler *handler;
>>>>> +    int i;
>>>>> +
>>>>> +    lockdep_assert_held(&profile_lock);
>>>>> +    handler = dev_get_drvdata(dev);
>>>>> +    for_each_set_bit(i, handler->choices, PLATFORM_PROFILE_LAST)
>>>>> +        *choices |= BIT(i);
>>>>
>>>> Maybe just copying the bitmask would be enough here? In this case we
>>>> could also drop
>>>> this function as well.
>>>
>>> Right now this could work, but choices and the use of it has gone
>>> through great lengths to ensure that once there are too many profiles
>>> it automatically becomes a bigger variable.
>>>
>>>     unsigned long choices[BITS_TO_LONGS(PLATFORM_PROFILE_LAST)];
>>>
>>> So I would rather keep this as is.
>>>
>> I think users of this function can do the locking themself and
>> instead use the functions from bitmap.h. Because _get_class_choices()
>> will break once "choices" becomes bigger.
>>
>
> I am thinking it's better to just switch explicitly to an 'unsigned
> long' and add a static check that all profiles fit.  If ever they
> don't fit, the code can be overhauled at that point.
>
> And yes _get_class_choices can go away then, and this is a lot simpler.

Ok.