linux-kernel - Re: [RFC] ACPI: Add GPIO-signaled event simulator.

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Date:	Fri, 8 Aug 2014 14:36:02 +0200
From:	Linus Walleij <linus.walleij@...aro.org>
To:	Tomasz Nowicki <tomasz.nowicki@...aro.org>,
	Mika Westerberg <mika.westerberg@...ux.intel.com>,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>
Cc:	Alexandre Courbot <gnurou@...il.com>,
	ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linaro-acpi@...ts.linaro.org" <linaro-acpi@...ts.linaro.org>
Subject: Re: [RFC] ACPI: Add GPIO-signaled event simulator.

On Thu, Jul 24, 2014 at 5:51 PM, Tomasz Nowicki
<tomasz.nowicki@...aro.org> wrote:

> GPIO signaled events is quite new thing in Linux kernel.
> AFAIK, there are not many board which can take advantage of it.
> However, GPIO events are very useful feature during work on ACPI
> subsystems.

Overall this seems like a pretty nice debug feature.

> This commit emulates GPIO h/w behaviour and consists on read/write
> operation to debugfs file. GPIO device instance is still required in DSDT
> table along with _AEI resources and event methods.
>
> Reading from file provides pin to GPIO device map e.g. :
> $ cat /sys/kernel/debug/acpi/gpio_event
> GPIO device name: /__SB.GPI0
> Available GPIO pin map:
> /__SB.GPI0 <-> pin 0x100
>
> Based on that, user can trigger method corresponding to device pin number:
> $ echo "/__SB.GPI0 0x100" > /sys/kernel/debug/acpi/gpio_event

I need input from Rafael and Mika as to whether this is a
good interface.

It seems a bit confusing for me: why do you have to extract
a number from one file and then insert the same magic number
somewhere else?

Yours,
Linus Walleij
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