linux-kernel - Re: [PATCH v7 1/7] MAINTAINERS: Add Advantech AHC1EC0 embedded controller entry

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Message-ID: <cf181436-152c-7cd8-76cf-350705cd2bcb@redhat.com>
Date:   Thu, 6 May 2021 11:38:46 +0200
From:   Hans de Goede <hdegoede@...hat.com>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     Campion Kang <campion.kang@...antech.com.tw>,
        Lee Jones <lee.jones@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Gross <mgross@...ux.intel.com>,
        Wim Van Sebroeck <wim@...ux-watchdog.org>,
        Guenter Roeck <linux@...ck-us.net>,
        Jean Delvare <jdelvare@...e.com>,
        Jonathan Corbet <corbet@....net>,
        devicetree <devicetree@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-watchdog@...r.kernel.org, linux-hwmon@...r.kernel.org,
        Linux Documentation List <linux-doc@...r.kernel.org>,
        Platform Driver <platform-driver-x86@...r.kernel.org>,
        AceLan Kao <chia-lin.kao@...onical.com>
Subject: Re: [PATCH v7 1/7] MAINTAINERS: Add Advantech AHC1EC0 embedded
 controller entry

Hi,

On 5/6/21 11:23 AM, Andy Shevchenko wrote:
> On Thu, May 6, 2021 at 11:48 AM Hans de Goede <hdegoede@...hat.com> wrote:
>> I'm replying here since this series has no cover-letter, for
>> the next version for a series touching so many different
>> sub-systems it would be good to start with a cover-letter
>> providing some background info on the series.
>>
>> I see this is binding to an ACPI device, yet it is also using
>> devicetree bindings and properties.
>>
>> So I take it this means that your ACPI tables are using the
>> optional capability of embedded device-tree blobs inside the
>> ACPI tables ?
>>
>> That is an unusual combination on a x86 device, note it is
>> not wrong
> 
> It's actually not okay. We have agreed at some point with DT people,
> that ACPI should not use non-native variants of natively supported
> things. For example, it shouldn't use "interrupt" property for IOxAPIC
> (or xIC) provided interrupts, rather Interrupt() has to be used and so
> on.

Right, but that is not the case here, they are using 2 device-tree
properties (1), from patch 3/7:

+properties:
+  compatible:
+    const: advantech,ahc1ec0
+
+  advantech,hwmon-profile:
+    description:
+      The number of sub-devices specified in the platform. Defines for the
+      hwmon profiles can found in dt-bindings/mfd/ahc1ec0-dt.
+    $ref: /schemas/types.yaml#/definitions/uint32
+    maxItems: 1
+
+  advantech,has-watchdog:
+    description:
+      Some implementations of the EC include a watchdog used to monitor the
+      system. This boolean flag is used to specify whether this watchdog is
+      present or not. Default is true, otherwise set to false.
+    type: boolean


>> but AFAIK you are the first to do this on x86.
> 
> No, not the first. Once Intel tried to invent the pin control
> configuration and muxing properties in ACPI, it was luckily rejected
> (ACPI 6.x OTOH provides a set of special resources for that).
> 
> So, NAK from me, *if* it's really the case. ACPI tables must be revisited.

AFAIK Advantech are not defining things for which an ACPI standard exists,
although these 2 properties might just as well may be 2 simple ACPI integer
methods, which would actually make things a bit simpler (.e.g it would
allow dropping patch 2/7 and 3/7 from the set).

Campion, any reason why you went this route; and can the ACPI tables
still be changed? 

Regards,

Hans