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

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Date:	Tue, 24 May 2016 09:09:38 +0200
From:	Pali Rohár <pali.rohar@...il.com>
To:	Andrei Borzenkov <arvidjaar@...il.com>
Cc:	Gabriele Mazzotta <gabriele.mzt@...il.com>,
	Darren Hart <dvhart@...radead.org>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	"D. Jared Dominguez" <Jared_Dominguez@...l.com>,
	"platform-driver-x86@...r.kernel.org" 
	<platform-driver-x86@...r.kernel.org>,
	Alex Hung <alex.hung@...onical.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3] dell-rbtn: Ignore ACPI notifications if device is
 suspended

On Tuesday 24 May 2016 06:48:41 Andrei Borzenkov wrote:
> 24.05.2016 02:03, Gabriele Mazzotta пишет:
> > On 24/05/2016 00:22, Pali Rohár wrote:
> >> On Tuesday 24 May 2016 00:17:15 Darren Hart wrote:
> >>> On Tue, May 24, 2016 at 12:06:03AM +0200, Pali Rohár wrote:
> >>>> On Monday 23 May 2016 23:26:55 Darren Hart wrote:
> >>>>> I've queued this. Thanks for your patience.
> >>>>
> >>>> Ok, In that case I would update comments in patch to try it more
> >>>> clear what code is doing.
> >>>
> >>> I thought I had your approval on this one Pali. Apologies if that was
> >>> not the case. Did I miss a change request from you?
> >>>
> >>> If so, please point me at it, and I'll dequeue this one and wait for
> >>> an updated one.
> >>
> >> I just wanted to review that code from somebody else and decide if 
> >> accept it or not. Because I was not sure if it is OK...
> >>
> >> But there was no objection, so patch is OK.
> >>
> >> And I pointed that patch could have better comments to describe what it 
> >> is doing as at first time I was confused.
> >>
> >> So I believe that you can update patch in your queue with new version 
> >> which just change comments in source code (without functional changes).
> >>
> > 
> > Something such as the following?
> > Feel free to reword the comments if you have something better in mind.
> > 
> > ---
> >  drivers/platform/x86/dell-rbtn.c | 56 ++++++++++++++++++++++++++++++++++++++++
> >  1 file changed, 56 insertions(+)
> > 
> > diff --git a/drivers/platform/x86/dell-rbtn.c b/drivers/platform/x86/dell-rbtn.c
> > index 331d63c..e0208ba 100644
> > --- a/drivers/platform/x86/dell-rbtn.c
> > +++ b/drivers/platform/x86/dell-rbtn.c
> > @@ -28,6 +28,7 @@ struct rbtn_data {
> >  	enum rbtn_type type;
> >  	struct rfkill *rfkill;
> >  	struct input_dev *input_dev;
> > +	bool suspended;
> >  };
> >  
> >  
> > @@ -235,9 +236,55 @@ static const struct acpi_device_id rbtn_ids[] = {
> >  	{ "", 0 },
> >  };
> >  
> > +#ifdef CONFIG_PM_SLEEP
> > +static void ACPI_SYSTEM_XFACE rbtn_acpi_clear_flag(void *context)

I would rename this function to rbtn_clear_suspended_flag.

> > +{
> > +	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;
> > +
> > +	/*
> > +	 * Upon resume, some BIOSes autonomously send an ACPI notification
> > +	 * that triggers an unwanted input event. In order to ignore it,
> > +	 * we use a flag that we set at suspend and clear once we have
> > +	 * received the extra notification. Since ACPI notifications are
> > +	 * delivered asynchronously to drivers, we clear the flag from the
> > +	 * workqueue used to deliver the notifications. This should be enough
> > +	 * to guarantee that the flag is cleared only after we received the
> > +	 * extra notification, if any.
> > +	 */
> 
> "guarantee" is rather strong word here. We really do not know anything
> how and when these notifications are generated by firmware, so can only
> hope. But otherwise this explains what this patch intends to do (so that
> even me finally understood it :)

Yes, thats better.

> > +	status = acpi_os_execute(OSL_NOTIFY_HANDLER,
> > +			 rbtn_acpi_clear_flag, rbtn_data);
> > +	if (ACPI_FAILURE(status))
> > +		rbtn_data->suspended = false;

And here rbtn_clear_suspended_flag(rbtn_data) call instead direct
assignment.

> > +
> > +	return 0;
> > +}
> > +#endif
> > +
> > +static SIMPLE_DEV_PM_OPS(rbtn_pm_ops, rbtn_suspend, rbtn_resume);
> > +
> >  static struct acpi_driver rbtn_driver = {
> >  	.name = "dell-rbtn",
> >  	.ids = rbtn_ids,
> > +	.drv.pm = &rbtn_pm_ops,
> >  	.ops = {
> >  		.add = rbtn_add,
> >  		.remove = rbtn_remove,
> > @@ -399,6 +446,15 @@ static void rbtn_notify(struct acpi_device *device, u32 event)
> >  {
> >  	struct rbtn_data *rbtn_data = device->driver_data;
> >  
> > +	/*
> > +	 * Some BIOSes send autonomously a notification at resume.
> > +	 * Ignore it to prevent unwanted input events.
> > +	 */
> > +	if (rbtn_data->suspended) {
> > +		dev_dbg(&device->dev, "ACPI notification ignored\n");
> > +		return;
> > +	}
> > +
> >  	if (event != 0x80) {
> >  		dev_info(&device->dev, "Received unknown event (0x%x)\n",
> >  			 event);
> > 
> 

-- 
Pali Rohár
pali.rohar@...il.com