linux-kernel - Re: [PATCH v3] dell-rbtn: Ignore ACPI notifications if device is suspended

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Date:	Thu, 24 Mar 2016 12:24:56 +0100
From:	Gabriele Mazzotta <gabriele.mzt@...il.com>
To:	Pali Rohár <pali.rohar@...il.com>
Cc:	Darren Hart <dvhart@...radead.org>,
	"D. Jared Dominguez" <Jared_Dominguez@...l.com>,
	"platform-driver-x86@...r.kernel.org" 
	<platform-driver-x86@...r.kernel.org>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Alex Hung <alex.hung@...onical.com>,
	Andrei Borzenkov <arvidjaar@...il.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3] dell-rbtn: Ignore ACPI notifications if device is suspended

2016-03-24 10:39 GMT+01:00 Pali Rohár <pali.rohar@...il.com>:
> On Monday 21 March 2016 16:13:34 Gabriele Mazzotta wrote:
>> 2016-03-21 13:17 GMT+01:00 Pali Rohár <pali.rohar@...il.com>:
>> > On Friday 18 March 2016 23:44:23 Gabriele Mazzotta wrote:
>> >> +#ifdef CONFIG_PM_SLEEP
>> >> +static void ACPI_SYSTEM_XFACE rbtn_acpi_clear_flag(void *context)
>> >> +{
>> >> +     struct rbtn_data *rbtn_data = context;
>> >> +
>> >> +     rbtn_data->suspended = false;
>> >> +}
>> >> +
>> >> +static int rbtn_suspend(struct device *dev)
>> >> +{
>> >> +     struct acpi_device *device = to_acpi_device(dev);
>> >> +     struct rbtn_data *rbtn_data = acpi_driver_data(device);
>> >> +
>> >> +     rbtn_data->suspended = true;
>> >> +
>> >> +     return 0;
>> >> +}
>> >> +
>> >> +static int rbtn_resume(struct device *dev)
>> >> +{
>> >> +     struct acpi_device *device = to_acpi_device(dev);
>> >> +     struct rbtn_data *rbtn_data = acpi_driver_data(device);
>> >> +     acpi_status status;
>> >> +
>> >> +     /*
>> >> +      * Clear the flag only after we received the extra
>> >> +      * ACPI notification.
>> >> +      */
>> >> +     status = acpi_os_execute(OSL_NOTIFY_HANDLER,
>> >> +                      rbtn_acpi_clear_flag, rbtn_data);
>> >> +     if (ACPI_FAILURE(status))
>> >> +             rbtn_data->suspended = false;
>> >
>> > I case when acpi_os_execute success it calls rbtn_acpi_clear_flag,
>> > right? And that will set suspended to false. When acpi_os_execute fails,
>> > then it set suspended too to false... Then whole acpi_os_execute doing
>> > just "barrier" after which suspended flag can be set to false. So I
>> > think rbtn_acpi_clear_flag function is not needed here.
>> >
>> > Cannot you pass NULL or empty function pointer as callback? Or what was
>> > reason to do that flag clearing at "two places"?
>>
>> acpi_os_execute doesn't wait for the callback to be executed, so
>> I can't clear the flag from rbtn_resume.
>
> acpi_os_execute calls callback asynchronously later? Or what exactly do it?

In this case, it adds the callback to the kacpi_notify_wq workqueue
for deferred execution.

> --
> Pali Rohár
> pali.rohar@...il.com