linux-kernel - Re: [RFC PATCH] gpio: support for GPIO forwarding

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Date:	Wed, 25 Feb 2015 10:34:45 +0900
From:	Alexandre Courbot <gnurou@...il.com>
To:	David Cohen <david.a.cohen@...ux.intel.com>
Cc:	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Linus Walleij <linus.walleij@...aro.org>,
	Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	Darren Hart <dvhart@...ux.intel.com>,
	Arnd Bergmann <arnd@...db.de>,
	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
	Mika Westerberg <mika.westerberg@...ux.intel.com>,
	"linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	ACPI Devel Maling List <linux-acpi@...r.kernel.org>
Subject: Re: [RFC PATCH] gpio: support for GPIO forwarding

On Wed, Feb 25, 2015 at 5:34 AM, David Cohen
<david.a.cohen@...ux.intel.com> wrote:
> Hi,
>
>> If we decide to go ahead with the solution proposed by this patch for
>> practical reasons (which are good reasons indeed), I still have one
>> problem with its current form.
>>
>> As the discussion highlighted, this is an ACPI problem, so I'd very
>> much like it to be confined to the ACPI GPIO code, to be enabled only
>> when ACPI is, and to use function names that start with acpi_gpio. The
>> current implementation leverages platform lookup, making said lookup
>> less efficient in the process and bringing confusion about its
>> purpose. Although the two processes are indeed similar, they are
>> separate things: one is a legitimate way to map GPIOs, the other is a
>> fixup for broken firmware.
>>
>> I suppose we all agree this is a hackish fix, so let's confine it as
>> much as we can.
>
> Are we considering MFD cases hackish as well?
> i.e. if we have a driver that needs to register children devices and this
> driver needs to pass GPIO to a child.

In that case wouldn't the GPIO be best defined in the child node
itself, for the child device's driver to directly probe?
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