linux-kernel - Re: [PATCH v3] ACPI: Force I2C to be selected as a built-in module

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Message-ID: <ae7f4499-d697-6703-52d5-7ab6d7a4b150@codeaurora.org>
Date:   Thu, 25 Jan 2018 11:32:31 -0500
From:   Sinan Kaya <okaya@...eaurora.org>
To:     "Rafael J. Wysocki" <rafael@...nel.org>
Cc:     ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        Timur Tabi <timur@...eaurora.org>,
        Eric Auger <eric.auger@...hat.com>,
        Hans de Goede <hdegoede@...hat.com>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Wolfram Sang <wsa@...-dreams.de>,
        linux-i2c <linux-i2c@...r.kernel.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Len Brown <lenb@...nel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3] ACPI: Force I2C to be selected as a built-in module

On 1/25/2018 11:25 AM, Rafael J. Wysocki wrote:
> On Thu, Jan 25, 2018 at 4:43 PM, Sinan Kaya <okaya@...eaurora.org> wrote:
>> From: Auger Eric <eric.auger@...hat.com>
>>
>> If I2C is built as a module, ACPI_I2C_OPREGION cannot be set
>> and any ACPI opregion calls targeting I2C fail with no opregion found.
>>
>> Commit da3c6647ee08 ("I2C/ACPI: Clean up I2C ACPI code and Add
>> CONFIG_I2C_ACPI config") says following:
>>
>> "Current there is a race between removing I2C ACPI operation region
>> and ACPI AML code accessing."
>>
>> This patch forces core I2C support to be compiled as a built-in
>> module if ACPI is selected as code is not ready for dynamic module
>> removal.
>>
>> Signed-off-by: Eric Auger <eric.auger@...hat.com>
>> Signed-off-by: Sinan Kaya <okaya@...eaurora.org>
>> ---
>>  drivers/acpi/Kconfig | 2 ++
>>  1 file changed, 2 insertions(+)
>>
>> diff --git a/drivers/acpi/Kconfig b/drivers/acpi/Kconfig
>> index 4650539..5b48098 100644
>> --- a/drivers/acpi/Kconfig
>> +++ b/drivers/acpi/Kconfig
>> @@ -9,6 +9,8 @@ menuconfig ACPI
>>         depends on IA64 || X86 || ARM64
>>         depends on PCI
>>         select PNP
>> +       # force building I2C in on ACPI systems, for opregion availability
>> +       imply I2C
>>         default y if (IA64 || X86)
>>         help
>>           Advanced Configuration and Power Interface (ACPI) support for
>> --
> 
> I'm not sure how much this helps.
> 
> I2C opregions will only work if the requisite I2C controller driver is
> present anyway and this change doesn't guarantee that AFAIC> 
> OTOH, there are systems using ACPI without I2C opregions, so are we
> really better off by forcing everybody using ACPI to also build I2C?

I was trying to find a good balance by choosing imply instead of select.

If an OS chooses to include an I2C driver as a module (most distros do),
core-i2c functionality becomes a built-in module with ACPI.

If an OS doesn't choose any I2C drivers either built-in/module, then I2C core
functionality wouldn't be selected; right?

> 
> Thanks,
> Rafael
> 


-- 
Sinan Kaya
Qualcomm Datacenter Technologies, Inc. as an affiliate of Qualcomm Technologies, Inc.
Qualcomm Technologies, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project.