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

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Date:   Tue, 30 Jan 2018 11:13:44 +1000
From:   Andrew Cooks <andrew.cooks@...ngear.com>
To:     Andy Shevchenko <andy.shevchenko@...il.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

Hi Andy

Thanks for the review!

On 29/01/18 23:30, Andy Shevchenko wrote:
> 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));

That seems much cleaner, but it doesn't seem to do what I need (my devices don't show up). I'm still investigating.

> 
> ?
> 
> 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++);
> }
>