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

[Rafael J. Wysocki]

On Thu, Jan 25, 2018 at 4:43 PM, Sinan Kaya <okaya@xxxxxxxxxxxxxx> wrote:
> From: Auger Eric <eric.auger@xxxxxxxxxx>
>
> 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@xxxxxxxxxx>
> Signed-off-by: Sinan Kaya <okaya@xxxxxxxxxxxxxx>
> ---
>  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 AFAICS.

OTOH, there are systems using ACPI without I2C opregions, so are we
really better off by forcing everybody using ACPI to also build I2C?

Thanks,
Rafael