linux-kernel - Re: [PATCH v3 5/6] thermal/drivers/acpi: Make cross dev link optional by configuration

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Message-ID: <7fd7df2d-f473-c0fd-5c3c-40d0fb697db7@linaro.org>
Date:   Tue, 18 Apr 2023 15:44:44 +0200
From:   Daniel Lezcano <daniel.lezcano@...aro.org>
To:     "Rafael J. Wysocki" <rafael@...nel.org>
Cc:     rui.zhang@...el.com, linux-kernel@...r.kernel.org,
        linux-pm@...r.kernel.org, Len Brown <lenb@...nel.org>,
        "open list:ACPI" <linux-acpi@...r.kernel.org>
Subject: Re: [PATCH v3 5/6] thermal/drivers/acpi: Make cross dev link optional
 by configuration

On 18/04/2023 15:38, Rafael J. Wysocki wrote:
> On Thu, Apr 13, 2023 at 1:47 PM Daniel Lezcano
> <daniel.lezcano@...aro.org> wrote:
>>
>> The ACPI thermal driver creates a link in the thermal zone device
>> sysfs directory pointing to the device sysfs directory. At the same
>> time, it creates a back pointer link from the device to the thermal
>> zone device sysfs directory.
>>
>>  From a generic perspective, having a device pointer in the sysfs
>> thermal zone directory may make sense. But the opposite is not true as
>> the same driver can be related to multiple thermal zones.
>>
>> The usage of these information is very specific to ACPI and it is
>> questionable if they are really needed.
>>
>> Let's make the code optional and disable it by default. If it hurts,
>> we will revert this change.
>>
>> Signed-off-by: Daniel Lezcano <daniel.lezcano@...aro.org>
>> ---
>>   drivers/acpi/Kconfig   | 13 +++++++++
>>   drivers/acpi/thermal.c | 62 ++++++++++++++++++++++++++++--------------
>>   2 files changed, 55 insertions(+), 20 deletions(-)
>>
>> diff --git a/drivers/acpi/Kconfig b/drivers/acpi/Kconfig
>> index ccbeab9500ec..7df4e18f06ef 100644
>> --- a/drivers/acpi/Kconfig
>> +++ b/drivers/acpi/Kconfig
>> @@ -336,6 +336,19 @@ config ACPI_THERMAL
>>            To compile this driver as a module, choose M here:
>>            the module will be called thermal.
>>
>> +config ACPI_THERMAL_SYSFS_ADDON
>> +       bool "Enable thermal sysfs addon"
>> +       depends on ACPI_THERMAL
>> +       def_bool n
>> +       help
>> +        Enable sysfs extra information added in the thermal zone and
>> +        the driver specific sysfs directories. That could be a link
>> +        to the associated thermal zone as well as a link pointing to
>> +        the device from the thermal zone. By default those are
>> +        disabled and are candidate for removal, if you need these
>> +        information anyway, enable the option or upgrade the
>> +        userspace program using them.
>> +
> 
> I don't think that the Kconfig option is appropriate and the help text
> above isn't really helpful.

I'm sorry, I'm missing something. Don't we want to make these sysfs 
extra information optional and disable them by default ?

>>   config ACPI_PLATFORM_PROFILE
>>          tristate
>>
>> diff --git a/drivers/acpi/thermal.c b/drivers/acpi/thermal.c
>> index 5763db4528b8..30fe189d04f8 100644
>> --- a/drivers/acpi/thermal.c
>> +++ b/drivers/acpi/thermal.c
>> @@ -787,9 +787,44 @@ static struct thermal_zone_device_ops acpi_thermal_zone_ops = {
>>          .critical = acpi_thermal_zone_device_critical,
>>   };
>>
>> +#ifdef CONFIG_ACPI_THERMAL_SYSFS_ADDON
> 
> I agree with moving the code in question to separate functions, but I
> don't agree with putting it under the Kconfig option.

Do you mean use IS_ENABLED check like what is done with Menlow patch 6 ?

[ ... ]


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