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

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Date:	Mon, 18 Aug 2014 11:31:53 +0200
From:	Tomasz Nowicki <tomasz.nowicki@...aro.org>
To:	Alexandre Courbot <gnurou@...il.com>,
	Mika Westerberg <mika.westerberg@...ux.intel.com>
CC:	Linus Walleij <linus.walleij@...aro.org>,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.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 12.08.2014 16:15, Alexandre Courbot wrote:
> On Tue, Aug 12, 2014 at 3:01 AM, Mika Westerberg
> <mika.westerberg@...ux.intel.com> wrote:
>> On Fri, Aug 08, 2014 at 02:36:02PM +0200, Linus Walleij wrote:
>>> 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.
>>
>> Maybe it would make sense to move this into drivers/gpio/gpiolib-acpi.c
>> and hide it behind some Kconfig entry?
>
> I actually like that this feature is contained in its own file - it
> makes it easier to Kconfig-isolate and keeps the base ACPI code short
> and readable. We spent some effort decoupling the sysfs and legacy
> interfaces from the main gpiolib source file, let's keep that policy
> going. ;)

I will keep that isolation.

>
> Maybe the source file could be renamed to highlight the fact this is
> an ACPI-only feature, e.g. gpio-acpi-evt-emu.c? (let's also use '-' as
> separator since this is what all GPIO drivers do).
>

Yes, I will rename it as you suggested. I will address all comments 
based on feedback I have got and send another version. Thanks!

Regards,
Tomasz Nowicki
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