linux-kernel - Re: [PATCH v2 5/5] gpio / ACPI: Add support for ACPI GPIO operation regions

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Message-ID: <20140314111151.GH5018@intel.com>
Date:	Fri, 14 Mar 2014 13:11:51 +0200
From:	Mika Westerberg <mika.westerberg@...ux.intel.com>
To:	Linus Walleij <linus.walleij@...aro.org>
Cc:	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Alexandre Courbot <gnurou@...il.com>,
	Lan Tianyu <tianyu.lan@...el.com>,
	Lv Zheng <lv.zheng@...el.com>, Alan Cox <alan.cox@...el.com>,
	Mathias Nyman <mathias.nyman@...ux.intel.com>,
	ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 5/5] gpio / ACPI: Add support for ACPI GPIO operation
 regions

On Fri, Mar 14, 2014 at 11:53:30AM +0100, Linus Walleij wrote:
> On Thu, Mar 13, 2014 at 4:18 PM, Mika Westerberg
> <mika.westerberg@...ux.intel.com> wrote:
> > On Thu, Mar 13, 2014 at 03:32:01PM +0100, Linus Walleij wrote:
> 
> >> > +                       case ACPI_IO_RESTRICT_OUTPUT:
> >> > +                               gpiod_direction_output(desc, pull);
> >>
> >> Can you explain why the fact that the line is pulled down affects the
> >> default output value like this? I don't get it.
> >
> > That's the thing - ACPI doesn't tell us what is the initial value of the
> > pin. There is no such field in GpioIo() resource.
> >
> > So I'm assuming here that if it says that the pin is pulled up, the default
> > value will be high.
> 
> OK! So exactly that statement is what I want to see as a comment
> in this switch case.

Sure. I'll add that comment to the next version of this patch.
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