linux-kernel - Re: [PATCH v2 1/1] gpio: gpio-wcove: Fix GPIO control register offset calculation

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Message-ID: <20170629202857.359bec9d@alans-desktop>
Date:   Thu, 29 Jun 2017 20:28:57 +0100
From:   Alan Cox <gnomes@...rguk.ukuu.org.uk>
To:     Linus Walleij <linus.walleij@...aro.org>
Cc:     Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        Hans de Goede <hdegoede@...hat.com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        "linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Sathyanarayanan Kuppuswamy Natarajan <sathyaosid@...il.com>,
        Graeme Gregory <graeme.gregory@...aro.org>
Subject: Re: [PATCH v2 1/1] gpio: gpio-wcove: Fix GPIO control register
 offset calculation

> So where can I get a handle on the people inside Intel who are obviously
> using ACPI GPIO class for shoehorning what we in the linux kernel call
> syscon or register bit misc access into the GPIO ACPI container just
> because they feel it is convenient?

It's a Windowsism and since Windows is the primary OS shipped the vendors
of client platforms do what is needed to make Windows work nicely.

> They need to invent a NEW ACPI four-character thing and call that
> "misc register bit" (_MRB?) or whatever and have it bind to syscon.
> This is not working.

Short of Microsoft adopting such a standard I don't think it would make
any difference (beyond making life worse because you'd have a new _MRB
that wasn't used by Windows so nobody ever tested).

> It feels like I am starting to maintain Intel's swiss army knife for misc
> register manipulation, and that should not be done by "virtual GPIO"
> because just look at it:

It's an ACPIism not an Intelism. I expect it's there on other vendors
devices and the same things will pop up as Windows/ARM platforms with
ACPI appear.

> General-purpose input/output - yeah that sounds like something
> going in/out of the system right?

It's become an ACPI interface for controlling all sorts of system state
in a way that works nicely in Windows. Rightly or wrongly that's the
situation and we are still the tail not the dog.

Alan