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

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  [PATCH v3] dell-rbtn: Ignore ACPI notifications if device is suspended Gabriele Mazzotta <gabriele.mzt@gmail.com> - 2016-03-18 23:50 +0100
    Re: [PATCH v3] dell-rbtn: Ignore ACPI notifications if device is  suspended Pali Rohár <pali.rohar@gmail.com> - 2016-03-21 13:20 +0100
      Re: [PATCH v3] dell-rbtn: Ignore ACPI notifications if device is suspended Gabriele Mazzotta <gabriele.mzt@gmail.com> - 2016-03-21 16:20 +0100
        Re: [PATCH v3] dell-rbtn: Ignore ACPI notifications if device is  suspended Pali Rohár <pali.rohar@gmail.com> - 2016-03-24 10:40 +0100
          Re: [PATCH v3] dell-rbtn: Ignore ACPI notifications if device is suspended Gabriele Mazzotta <gabriele.mzt@gmail.com> - 2016-03-24 12:30 +0100
            Re: [PATCH v3] dell-rbtn: Ignore ACPI notifications if device is  suspended Darren Hart <dvhart@infradead.org> - 2016-03-28 19:40 +0200
              Re: [PATCH v3] dell-rbtn: Ignore ACPI notifications if device is suspended Gabriele Mazzotta <gabriele.mzt@gmail.com> - 2016-03-28 20:00 +0200
                Re: [PATCH v3] dell-rbtn: Ignore ACPI notifications if device is  suspended Darren Hart <dvhart@infradead.org> - 2016-03-28 21:00 +0200
                  Re: [PATCH v3] dell-rbtn: Ignore ACPI notifications if device is suspended Gabriele Mazzotta <gabriele.mzt@gmail.com> - 2016-03-28 21:50 +0200
                    Re: [PATCH v3] dell-rbtn: Ignore ACPI notifications if device is  suspended Darren Hart <dvhart@infradead.org> - 2016-03-29 07:30 +0200
                      Re: [PATCH v3] dell-rbtn: Ignore ACPI notifications if device is suspended Gabriele Mazzotta <gabriele.mzt@gmail.com> - 2016-03-29 13:20 +0200
              Re: [PATCH v3] dell-rbtn: Ignore ACPI notifications if device is suspended "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2016-03-29 15:10 +0200

#1360981 — [PATCH v3] dell-rbtn: Ignore ACPI notifications if device is suspended

Some BIOSes unconditionally send an ACPI notification to RBTN when the
system is resuming from suspend. This makes dell-rbtn send an input
event to userspace as if a function key was pressed. Prevent this by
ignoring all the notifications received while the device is suspended.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=106031
Signed-off-by: Gabriele Mazzotta <gabriele.mzt@gmail.com>
---
Same as v2 with some comments

 drivers/platform/x86/dell-rbtn.c | 50 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 50 insertions(+)

diff --git a/drivers/platform/x86/dell-rbtn.c b/drivers/platform/x86/dell-rbtn.c
index 5155278..b144b8c 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;
 };
 
 
@@ -220,9 +221,49 @@ static const struct acpi_device_id rbtn_ids[] = {
 	{ "", 0 },
 };
 
+#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;
+
+	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,
@@ -384,6 +425,15 @@ 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);
-- 
2.8.0.rc3

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#1361760 — Re: [PATCH v3] dell-rbtn: Ignore ACPI notifications if device is suspended

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"?

> +	return 0;
> +}
> +#endif

-- 
Pali Rohár
pali.rohar@gmail.com

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#1361925

2016-03-21 13:17 GMT+01:00 Pali Rohár <pali.rohar@gmail.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.

>> +     return 0;
>> +}
>> +#endif
>
> --
> Pali Rohár
> pali.rohar@gmail.com

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#1364023 — Re: [PATCH v3] dell-rbtn: Ignore ACPI notifications if device is suspended

On Monday 21 March 2016 16:13:34 Gabriele Mazzotta wrote:
> 2016-03-21 13:17 GMT+01:00 Pali Rohár <pali.rohar@gmail.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?

-- 
Pali Rohár
pali.rohar@gmail.com

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#1364094

2016-03-24 10:39 GMT+01:00 Pali Rohár <pali.rohar@gmail.com>:
> On Monday 21 March 2016 16:13:34 Gabriele Mazzotta wrote:
>> 2016-03-21 13:17 GMT+01:00 Pali Rohár <pali.rohar@gmail.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@gmail.com

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#1365601 — Re: [PATCH v3] dell-rbtn: Ignore ACPI notifications if device is suspended

On Thu, Mar 24, 2016 at 12:24:56PM +0100, Gabriele Mazzotta wrote:
> 2016-03-24 10:39 GMT+01:00 Pali Rohár <pali.rohar@gmail.com>:
> > On Monday 21 March 2016 16:13:34 Gabriele Mazzotta wrote:
> >> 2016-03-21 13:17 GMT+01:00 Pali Rohár <pali.rohar@gmail.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.

+Rafael for context/advice on the use of acpi_os_execute here.

This is true, but a quick scan through that call path doesn't tell me why we
would need to call it here instead of just setting rbtn_data->suspended = false.
The comment suggests waiting for the event, but is that what this is doing? It
appears to me to be immediately scheduling the function to a work queue, not
waiting for the event notifier.

Also, since there is no indication to the user that a failure occurs, this
function is basically equivalent in the success and failure case (the success
case is just slower).

Am I missing something critical here?



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

-- 
Darren Hart
Intel Open Source Technology Center

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#1365613

2016-03-28 19:33 GMT+02:00 Darren Hart <dvhart@infradead.org>:
> On Thu, Mar 24, 2016 at 12:24:56PM +0100, Gabriele Mazzotta wrote:
>> 2016-03-24 10:39 GMT+01:00 Pali Rohár <pali.rohar@gmail.com>:
>> > On Monday 21 March 2016 16:13:34 Gabriele Mazzotta wrote:
>> >> 2016-03-21 13:17 GMT+01:00 Pali Rohár <pali.rohar@gmail.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.
>
> +Rafael for context/advice on the use of acpi_os_execute here.
>
> This is true, but a quick scan through that call path doesn't tell me why we
> would need to call it here instead of just setting rbtn_data->suspended = false.
> The comment suggests waiting for the event, but is that what this is doing? It
> appears to me to be immediately scheduling the function to a work queue, not
> waiting for the event notifier.
>
> Also, since there is no indication to the user that a failure occurs, this
> function is basically equivalent in the success and failure case (the success
> case is just slower).
>
> Am I missing something critical here?

Maybe saying that we are waiting for the extra event is not really
correct. Since the extra ACPI notification is processed by means
of kacpi_notify_wq, or at least that's my understanding, our callback
is likely going to be executed after we received the extra ACPI
notification. This was suggested by Rafael [2].

The problem with setting the flag directly from the resume callback
is that the extra notification might arrive after we cleared the
flag, causing spurious input events [1].

[1] http://article.gmane.org/gmane.linux.drivers.platform.x86.devel/8001
[2] http://article.gmane.org/gmane.linux.drivers.platform.x86.devel/8201

>
>>
>> > --
>> > Pali Rohár
>> > pali.rohar@gmail.com
>>
>
> --
> Darren Hart
> Intel Open Source Technology Center

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#1365635 — Re: [PATCH v3] dell-rbtn: Ignore ACPI notifications if device is suspended

On Mon, Mar 28, 2016 at 07:58:09PM +0200, Gabriele Mazzotta wrote:
> 2016-03-28 19:33 GMT+02:00 Darren Hart <dvhart@infradead.org>:
> > On Thu, Mar 24, 2016 at 12:24:56PM +0100, Gabriele Mazzotta wrote:
> >> 2016-03-24 10:39 GMT+01:00 Pali Rohár <pali.rohar@gmail.com>:
> >> > On Monday 21 March 2016 16:13:34 Gabriele Mazzotta wrote:
> >> >> 2016-03-21 13:17 GMT+01:00 Pali Rohár <pali.rohar@gmail.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.
> >
> > +Rafael for context/advice on the use of acpi_os_execute here.
> >
> > This is true, but a quick scan through that call path doesn't tell me why we
> > would need to call it here instead of just setting rbtn_data->suspended = false.
> > The comment suggests waiting for the event, but is that what this is doing? It
> > appears to me to be immediately scheduling the function to a work queue, not
> > waiting for the event notifier.
> >
> > Also, since there is no indication to the user that a failure occurs, this
> > function is basically equivalent in the success and failure case (the success
> > case is just slower).
> >
> > Am I missing something critical here?
> 
> Maybe saying that we are waiting for the extra event is not really
> correct. Since the extra ACPI notification is processed by means
> of kacpi_notify_wq, or at least that's my understanding, our callback
> is likely going to be executed after we received the extra ACPI
> notification. This was suggested by Rafael [2].

I see, the workqueue is run after the event is issued. If that's the case, how
are we ensured that it will get cleared? Isn't it only some systems that have
this problem?

What happens to the systems that do not send this event at resume? Does the
suspended flag remain set?

> 
> The problem with setting the flag directly from the resume callback
> is that the extra notification might arrive after we cleared the
> flag, causing spurious input events [1].
> 
> [1] http://article.gmane.org/gmane.linux.drivers.platform.x86.devel/8001
> [2] http://article.gmane.org/gmane.linux.drivers.platform.x86.devel/8201
> 
> >
> >>
> >> > --
> >> > Pali Rohár
> >> > pali.rohar@gmail.com
> >>
> >
> > --
> > Darren Hart
> > Intel Open Source Technology Center
> 

-- 
Darren Hart
Intel Open Source Technology Center

[toc] | [prev] | [next] | [standalone]

#1365647

2016-03-28 20:56 GMT+02:00 Darren Hart <dvhart@infradead.org>:
> On Mon, Mar 28, 2016 at 07:58:09PM +0200, Gabriele Mazzotta wrote:
>> 2016-03-28 19:33 GMT+02:00 Darren Hart <dvhart@infradead.org>:
>> > On Thu, Mar 24, 2016 at 12:24:56PM +0100, Gabriele Mazzotta wrote:
>> >> 2016-03-24 10:39 GMT+01:00 Pali Rohár <pali.rohar@gmail.com>:
>> >> > On Monday 21 March 2016 16:13:34 Gabriele Mazzotta wrote:
>> >> >> 2016-03-21 13:17 GMT+01:00 Pali Rohár <pali.rohar@gmail.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.
>> >
>> > +Rafael for context/advice on the use of acpi_os_execute here.
>> >
>> > This is true, but a quick scan through that call path doesn't tell me why we
>> > would need to call it here instead of just setting rbtn_data->suspended = false.
>> > The comment suggests waiting for the event, but is that what this is doing? It
>> > appears to me to be immediately scheduling the function to a work queue, not
>> > waiting for the event notifier.
>> >
>> > Also, since there is no indication to the user that a failure occurs, this
>> > function is basically equivalent in the success and failure case (the success
>> > case is just slower).
>> >
>> > Am I missing something critical here?
>>
>> Maybe saying that we are waiting for the extra event is not really
>> correct. Since the extra ACPI notification is processed by means
>> of kacpi_notify_wq, or at least that's my understanding, our callback
>> is likely going to be executed after we received the extra ACPI
>> notification. This was suggested by Rafael [2].
>
> I see, the workqueue is run after the event is issued. If that's the case, how
> are we ensured that it will get cleared? Isn't it only some systems that have
> this problem?
>
> What happens to the systems that do not send this event at resume? Does the
> suspended flag remain set?

The callback should be executed as long as acpi_os_execute doesn't
return an error. If the BIOS doesn't send the extra notification,
we uselessly wait for whatever was queued before our callback.

On my laptop, the interval between the call to acpi_os_execute and
the callback execution is ~200ms (rough existimation using a couple
of printks), so not really noticeable. It might be more on some other
systems, but I doubt anyone would notice.

>>
>> The problem with setting the flag directly from the resume callback
>> is that the extra notification might arrive after we cleared the
>> flag, causing spurious input events [1].
>>
>> [1] http://article.gmane.org/gmane.linux.drivers.platform.x86.devel/8001
>> [2] http://article.gmane.org/gmane.linux.drivers.platform.x86.devel/8201
>>
>> >
>> >>
>> >> > --
>> >> > Pali Rohár
>> >> > pali.rohar@gmail.com
>> >>
>> >
>> > --
>> > Darren Hart
>> > Intel Open Source Technology Center
>>
>
> --
> Darren Hart
> Intel Open Source Technology Center

[toc] | [prev] | [next] | [standalone]

#1365863 — Re: [PATCH v3] dell-rbtn: Ignore ACPI notifications if device is suspended

On Mon, Mar 28, 2016 at 09:41:09PM +0200, Gabriele Mazzotta wrote:
> 2016-03-28 20:56 GMT+02:00 Darren Hart <dvhart@infradead.org>:
> > On Mon, Mar 28, 2016 at 07:58:09PM +0200, Gabriele Mazzotta wrote:
> >> 2016-03-28 19:33 GMT+02:00 Darren Hart <dvhart@infradead.org>:
> >> > On Thu, Mar 24, 2016 at 12:24:56PM +0100, Gabriele Mazzotta wrote:
> >> >> 2016-03-24 10:39 GMT+01:00 Pali Rohár <pali.rohar@gmail.com>:
> >> >> > On Monday 21 March 2016 16:13:34 Gabriele Mazzotta wrote:
> >> >> >> 2016-03-21 13:17 GMT+01:00 Pali Rohár <pali.rohar@gmail.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.
> >> >
> >> > +Rafael for context/advice on the use of acpi_os_execute here.
> >> >
> >> > This is true, but a quick scan through that call path doesn't tell me why we
> >> > would need to call it here instead of just setting rbtn_data->suspended = false.
> >> > The comment suggests waiting for the event, but is that what this is doing? It
> >> > appears to me to be immediately scheduling the function to a work queue, not
> >> > waiting for the event notifier.
> >> >
> >> > Also, since there is no indication to the user that a failure occurs, this
> >> > function is basically equivalent in the success and failure case (the success
> >> > case is just slower).
> >> >
> >> > Am I missing something critical here?
> >>
> >> Maybe saying that we are waiting for the extra event is not really
> >> correct. Since the extra ACPI notification is processed by means
> >> of kacpi_notify_wq, or at least that's my understanding, our callback
> >> is likely going to be executed after we received the extra ACPI
> >> notification. This was suggested by Rafael [2].
> >
> > I see, the workqueue is run after the event is issued. If that's the case, how
> > are we ensured that it will get cleared? Isn't it only some systems that have
> > this problem?
> >
> > What happens to the systems that do not send this event at resume? Does the
> > suspended flag remain set?
> 
> The callback should be executed as long as acpi_os_execute doesn't
> return an error. If the BIOS doesn't send the extra notification,
> we uselessly wait for whatever was queued before our callback.
> 
> On my laptop, the interval between the call to acpi_os_execute and
> the callback execution is ~200ms (rough existimation using a couple
> of printks), so not really noticeable. It might be more on some other
> systems, but I doubt anyone would notice.

And what triggers the callback then? Some unrelated event triggering the
workqueue I presume? I don't care to tie the masking of these events to
unrelated ones. What guarantee do we have that they will fire? Is it possible
for that workqueue to be otherwise empty and not get triggered, effectively
disabling our events?

> 
> >>
> >> The problem with setting the flag directly from the resume callback
> >> is that the extra notification might arrive after we cleared the
> >> flag, causing spurious input events [1].
> >>
> >> [1] http://article.gmane.org/gmane.linux.drivers.platform.x86.devel/8001
> >> [2] http://article.gmane.org/gmane.linux.drivers.platform.x86.devel/8201
> >>

-- 
Darren Hart
Intel Open Source Technology Center

[toc] | [prev] | [next] | [standalone]

#1366166

2016-03-29 7:24 GMT+02:00 Darren Hart <dvhart@infradead.org>:
>
> On Mon, Mar 28, 2016 at 09:41:09PM +0200, Gabriele Mazzotta wrote:
> > 2016-03-28 20:56 GMT+02:00 Darren Hart <dvhart@infradead.org>:
> > > On Mon, Mar 28, 2016 at 07:58:09PM +0200, Gabriele Mazzotta wrote:
> > >> 2016-03-28 19:33 GMT+02:00 Darren Hart <dvhart@infradead.org>:
> > >> > On Thu, Mar 24, 2016 at 12:24:56PM +0100, Gabriele Mazzotta wrote:
> > >> >> 2016-03-24 10:39 GMT+01:00 Pali Rohár <pali.rohar@gmail.com>:
> > >> >> > On Monday 21 March 2016 16:13:34 Gabriele Mazzotta wrote:
> > >> >> >> 2016-03-21 13:17 GMT+01:00 Pali Rohár <pali.rohar@gmail.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.
> > >> >
> > >> > +Rafael for context/advice on the use of acpi_os_execute here.
> > >> >
> > >> > This is true, but a quick scan through that call path doesn't tell me why we
> > >> > would need to call it here instead of just setting rbtn_data->suspended = false.
> > >> > The comment suggests waiting for the event, but is that what this is doing? It
> > >> > appears to me to be immediately scheduling the function to a work queue, not
> > >> > waiting for the event notifier.
> > >> >
> > >> > Also, since there is no indication to the user that a failure occurs, this
> > >> > function is basically equivalent in the success and failure case (the success
> > >> > case is just slower).
> > >> >
> > >> > Am I missing something critical here?
> > >>
> > >> Maybe saying that we are waiting for the extra event is not really
> > >> correct. Since the extra ACPI notification is processed by means
> > >> of kacpi_notify_wq, or at least that's my understanding, our callback
> > >> is likely going to be executed after we received the extra ACPI
> > >> notification. This was suggested by Rafael [2].
> > >
> > > I see, the workqueue is run after the event is issued. If that's the case, how
> > > are we ensured that it will get cleared? Isn't it only some systems that have
> > > this problem?
> > >
> > > What happens to the systems that do not send this event at resume? Does the
> > > suspended flag remain set?
> >
> > The callback should be executed as long as acpi_os_execute doesn't
> > return an error. If the BIOS doesn't send the extra notification,
> > we uselessly wait for whatever was queued before our callback.
> >
> > On my laptop, the interval between the call to acpi_os_execute and
> > the callback execution is ~200ms (rough existimation using a couple
> > of printks), so not really noticeable. It might be more on some other
> > systems, but I doubt anyone would notice.
>
> And what triggers the callback then? Some unrelated event triggering the
> workqueue I presume? I don't care to tie the masking of these events to
> unrelated ones. What guarantee do we have that they will fire? Is it possible
> for that workqueue to be otherwise empty and not get triggered, effectively
> disabling our events?

acpi_os_execute creates a work item for the callback and adds it
to the kacpi_notify_wq workqueue. Nothing triggers it, it just
waits for its turn.

The BIOS sends the notification immediately at resume, so the work
item that handles it is likely going to get queued before our work
item. In my case, the notification is handled even before dell-rbtn
is resumed (and that's why the original worked fine for me).

> >
> > >>
> > >> The problem with setting the flag directly from the resume callback
> > >> is that the extra notification might arrive after we cleared the
> > >> flag, causing spurious input events [1].
> > >>
> > >> [1] http://article.gmane.org/gmane.linux.drivers.platform.x86.devel/8001
> > >> [2] http://article.gmane.org/gmane.linux.drivers.platform.x86.devel/8201
> > >>
>
> --
> Darren Hart
> Intel Open Source Technology Center

[toc] | [prev] | [next] | [standalone]

#1366259

On Monday, March 28, 2016 10:33:09 AM Darren Hart wrote:
> On Thu, Mar 24, 2016 at 12:24:56PM +0100, Gabriele Mazzotta wrote:
> > 2016-03-24 10:39 GMT+01:00 Pali Rohár <pali.rohar@gmail.com>:
> > > On Monday 21 March 2016 16:13:34 Gabriele Mazzotta wrote:
> > >> 2016-03-21 13:17 GMT+01:00 Pali Rohár <pali.rohar@gmail.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.
> 
> +Rafael for context/advice on the use of acpi_os_execute here.
> 
> This is true, but a quick scan through that call path doesn't tell me why we
> would need to call it here instead of just setting rbtn_data->suspended = false.
> The comment suggests waiting for the event, but is that what this is doing? It
> appears to me to be immediately scheduling the function to a work queue, not
> waiting for the event notifier.

I think this is supposed to work as a barrier.  That is, it will only run after
all events in the queue have been processed.

I'm not sure if that's necessary, though.

Thanks,
Rafael

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