linux-kernel - Re: [PATCH 3/3] i2c: add ACPI support for i2c-piix4

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Date:   Mon, 29 Jan 2018 15:30:47 +0200
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Andrew Cooks <andrew.cooks@...ngear.com>
Cc:     Jean Delvare <jdelvare@...e.com>, Wolfram Sang <wsa@...-dreams.de>,
        "open list:I2C/SMBUS CONTROLLER DRIVERS FOR PC" 
        <linux-i2c@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/3] i2c: add ACPI support for i2c-piix4

On Mon, Jan 29, 2018 at 5:54 AM, Andrew Cooks <andrew.cooks@...ngear.com> wrote:
> This enables the i2c-piix4 SMBus controller driver to enumerate I2C
> slave devices using ACPI. It builds on the related I2C mux device work
> in commit 8eb5c87a92c0 ("i2c: add ACPI support for I2C mux ports")
>
> In the i2c-piix4 driver the adapters are enumerated as:
>  Main SMBus adapter Port 0, Port 2, ..., aux port (i.e., ASF adapter)
>
> However, in the AMD BKDG documentation[1], the implied order of ports is:
>  Main SMBus adapter Port 0, ASF adapter, Port 2, Port 3, ...
>
> This ordering difference is unfortunate, and we assume that ACPI
> developers will use the Linux ordering.
>
> [1] 52740 BIOS and Kernel Developer's Guide (BKDG) for AMD Family 16h
> Models 30h-3Fh Processors

> +       if (has_acpi_companion(&dev->dev)) {
> +               acpi_preset_companion(&adap->dev,
> +                                     ACPI_COMPANION(&dev->dev),
> +                                     piix4_adapter_count++);
> +       }

Wouldn't be enough just following:

     ACPI_COMPANION_SET(&adap->dev, ACPI_COMPANION(&dev->dev));

?

Or if this increment is needed:

struct acpi_device *adev = ACPI_COMPANION(&dev->dev);

if (adev) {
    ACPI_COMPANION_SET(&adap->dev, adev);
    piix4_adapter_count++);
}

-- 
With Best Regards,
Andy Shevchenko