RE: [PATCH v7 1/2] ACPI / button: Fix an issue that the platform triggered reliable events may not be delivered to the userspace

["Zheng, Lv" <lv.zheng@intel.com>]

Hi, Rafael

> From: linux-acpi-owner@vger.kernel.org [mailto:linux-acpi-owner@vger.kernel.org] On Behalf Of Rafael J.
> Wysocki
> Subject: Re: [PATCH v7 1/2] ACPI / button: Fix an issue that the platform triggered reliable events
> may not be delivered to the userspace
> 
> On Tuesday, July 26, 2016 05:52:24 PM Lv Zheng wrote:
> > On most platforms, _LID returning value, lid open/close events are all
> > reliable, but there are exceptions. Some AML tables report wrong initial
> > lid state (Link 1), and some of them never report lid open state (Link 2).
> > The usage model on such buggy platforms is:
> > 1. The initial lid state returned from _LID is not reliable;
> > 2. The lid open event is not reliable;
> > 3. The lid close event is always reliable, used by the platform firmware to
> >    trigger OSPM power saving operations.
> > This usage model is not compliant to the Linux SW_LID model as the Linux
> > userspace is very strict to the reliability of the open events.
> >
> > In order not to trigger issues on such buggy platforms, the ACPI button
> > driver currently implements a lid_init_state=open quirk to send additional
> > "open" event after resuming. However, this is still not sufficient because:
> > 1. Some special usage models (e.x., the dark resume scenario) cannot be
> >    supported by this mode.
> > 2. If a "close" event is not used to trigger "suspend", then the subsequent
> >    "close" events cannot be seen by the userspace.
> > So we need to stop sending the additional "open" event and switch the
> > driver to lid_init_state=ignore mode and make sure the platform triggered
> > events can be reliably delivered to the userspace. The userspace programs
> > then can be changed to not to be strict to the "open" events on such buggy
> > platforms.
> >
> > Why will the subsequent "close" events be lost? This is because the input
> > layer automatically filters redundant events for switch events. Thus given
> > that the buggy AML tables do not guarantee paired "open"/"close" events,
> > the ACPI button driver currently is not able to guarantee that the platform
> > triggered reliable events can be always be seen by the userspace via
> > SW_LID.
> >
> > This patch adds a mechanism to insert lid events as a compensation for the
> > platform triggered ones to form a complete event switches in order to make
> > sure that the platform triggered events can always be reliably delivered
> > to the userspace. This essentially guarantees that the platform triggered
> > reliable "close" events will always be relibly delivered to the userspace.
> >
> > However this mechanism is not suitable for lid_init_state=open/method as
> > it should not send the complement switch event for the unreliable initial
> > lid state notification. 2 unreliable events can trigger unexpected
> > behavior. Thus this patch only implements this mechanism for
> > lid_init_state=ignore.
> >
> > Link 1: https://bugzilla.kernel.org/show_bug.cgi?id=89211
> >         https://bugzilla.kernel.org/show_bug.cgi?id=106151
> > Link 2: https://bugzilla.kernel.org/show_bug.cgi?id=106941
> > Signed-off-by: Lv Zheng <lv.zheng@intel.com>
> > Suggested-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
> > Cc: Benjamin Tissoires <benjamin.tissoires@gmail.com>
> > Cc: Bastien Nocera: <hadess@hadess.net>
> > Cc: linux-input@vger.kernel.org
> > ---
> >  drivers/acpi/button.c |   51 ++++++++++++++++++++++++++++++++++++++++++++++++-
> >  1 file changed, 50 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/acpi/button.c b/drivers/acpi/button.c
> > index 148f4e5..dca1806 100644
> > --- a/drivers/acpi/button.c
> > +++ b/drivers/acpi/button.c
> > @@ -19,6 +19,8 @@
> >   * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> >   */
> >
> > +#define pr_fmt(fmt) "ACPI : button: " fmt
> > +
> >  #include <linux/kernel.h>
> >  #include <linux/module.h>
> >  #include <linux/init.h>
> > @@ -104,6 +106,8 @@ struct acpi_button {
> >  	struct input_dev *input;
> >  	char phys[32];			/* for input device */
> >  	unsigned long pushed;
> > +	int last_state;
> > +	unsigned long last_time;
> 
> Why don't you use ktime_t here?

OK.
I'll update the patch with ktime interfaces.
And send it after tests.

Thanks,
Lv

> 
> >  	bool suspended;
> >  };
> >
> > @@ -111,6 +115,10 @@ static BLOCKING_NOTIFIER_HEAD(acpi_lid_notifier);
> >  static struct acpi_device *lid_device;
> >  static u8 lid_init_state = ACPI_BUTTON_LID_INIT_METHOD;
> >
> > +static unsigned long lid_report_interval __read_mostly = 500;
> > +module_param(lid_report_interval, ulong, 0644);
> > +MODULE_PARM_DESC(lid_report_interval, "Interval (ms) between lid key events");
> > +
> >  /* --------------------------------------------------------------------------
> >                                FS Interface (/proc)
> >     -------------------------------------------------------------------------- */
> > @@ -135,9 +143,48 @@ static int acpi_lid_notify_state(struct acpi_device *device, int state)
> >  	struct acpi_button *button = acpi_driver_data(device);
> >  	int ret;
> >
> > -	/* input layer checks if event is redundant */
> > +	if (button->last_state == !!state &&
> > +	    time_after(jiffies, button->last_time +
> > +				msecs_to_jiffies(lid_report_interval))) {
> 
> And ktime_after() here?
> 
> > +		/* Complain the buggy firmware */
> > +		pr_warn_once("The lid device is not compliant to SW_LID.\n");
> > +
> > +		/*
> > +		 * Send the unreliable complement switch event:
> > +		 *
> > +		 * On most platforms, the lid device is reliable. However
> > +		 * there are exceptions:
> > +		 * 1. Platforms returning initial lid state as "close" by
> > +		 *    default after booting/resuming:
> > +		 *     https://bugzilla.kernel.org/show_bug.cgi?id=89211
> > +		 *     https://bugzilla.kernel.org/show_bug.cgi?id=106151
> > +		 * 2. Platforms never reporting "open" events:
> > +		 *     https://bugzilla.kernel.org/show_bug.cgi?id=106941
> > +		 * On these buggy platforms, the usage model of the ACPI
> > +		 * lid device actually is:
> > +		 * 1. The initial returning value of _LID may not be
> > +		 *    reliable.
> > +		 * 2. The open event may not be reliable.
> > +		 * 3. The close event is reliable.
> > +		 *
> > +		 * But SW_LID is typed as input switch event, the input
> > +		 * layer checks if the event is redundant. Hence if the
> > +		 * state is not switched, the userspace cannot see this
> > +		 * platform triggered reliable event. By inserting a
> > +		 * complement switch event, it then is guaranteed that the
> > +		 * platform triggered reliable one can always be seen by
> > +		 * the userspace.
> > +		 */
> > +		if (lid_init_state == ACPI_BUTTON_LID_INIT_IGNORE) {
> > +			input_report_switch(button->input, SW_LID, state);
> > +			input_sync(button->input);
> > +		}
> > +	}
> > +	/* Send the platform triggered reliable event */
> >  	input_report_switch(button->input, SW_LID, !state);
> >  	input_sync(button->input);
> > +	button->last_state = !!state;
> > +	button->last_time = jiffies;
> 
> And ktime_get() here?
> 
> >
> >  	if (state)
> >  		pm_wakeup_event(&device->dev, 0);
> > @@ -407,6 +454,8 @@ static int acpi_button_add(struct acpi_device *device)
> >  		strcpy(name, ACPI_BUTTON_DEVICE_NAME_LID);
> >  		sprintf(class, "%s/%s",
> >  			ACPI_BUTTON_CLASS, ACPI_BUTTON_SUBCLASS_LID);
> > +		button->last_state = !!acpi_lid_evaluate_state(device);
> > +		button->last_time = jiffies;
> 
> And here?
> 
> >  	} else {
> >  		printk(KERN_ERR PREFIX "Unsupported hid [%s]\n", hid);
> >  		error = -ENODEV;
> >
> 
> Thanks,
> Rafael
> 
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