linux-kernel - Re: [PATCH v5 1/3] ACPI / button: Add missing event to keep SW_LID running without additional event loss

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Date:	Sat, 23 Jul 2016 14:37:07 +0200
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	Lv Zheng <lv.zheng@...el.com>
Cc:	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	Len Brown <len.brown@...el.com>, Lv Zheng <zetalog@...il.com>,
	linux-kernel@...r.kernel.org, linux-acpi@...r.kernel.org,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Benjamin Tissoires <benjamin.tissoires@...il.com>,
	"Bastien Nocera:" <hadess@...ess.net>, linux-input@...r.kernel.org
Subject: Re: [PATCH v5 1/3] ACPI / button: Add missing event to keep SW_LID running without additional event loss

On Friday, July 22, 2016 02:24:42 PM Lv Zheng wrote:
> There are several possibilities that a lid event can be lost. For example,
> EC event queue full, or the resume order of the underlying drivers.
> 
> When the event loss happens, new event may also be lost due to the type of
> the SW_LID (switch event). The 2nd loss is what we want to avoid.
> 
> This patch adds a mechanism to insert lid events as a compensation for the
> switch event nature of the lid events in order to avoid the 2nd loss.

Can you please provide a high-level description of the new mechanism here?

> 
> Signed-off-by: Lv Zheng <lv.zheng@...el.com>
> Cc: Dmitry Torokhov <dmitry.torokhov@...il.com>
> Cc: Benjamin Tissoires <benjamin.tissoires@...il.com>
> Cc: Bastien Nocera: <hadess@...ess.net>
> Cc: linux-input@...r.kernel.org
> ---
>  drivers/acpi/button.c |   21 ++++++++++++++++++++-
>  1 file changed, 20 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/acpi/button.c b/drivers/acpi/button.c
> index 148f4e5..41fd21d 100644
> --- a/drivers/acpi/button.c
> +++ b/drivers/acpi/button.c
> @@ -104,6 +104,8 @@ struct acpi_button {
>  	struct input_dev *input;
>  	char phys[32];			/* for input device */
>  	unsigned long pushed;
> +	int sw_last_state;
> +	unsigned long sw_last_time;
>  	bool suspended;
>  };
>  
> @@ -111,6 +113,10 @@ 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)
>     -------------------------------------------------------------------------- */
> @@ -133,11 +139,22 @@ static int acpi_lid_evaluate_state(struct acpi_device *device)
>  static int acpi_lid_notify_state(struct acpi_device *device, int state)
>  {
>  	struct acpi_button *button = acpi_driver_data(device);
> +	unsigned long sw_tout;
>  	int ret;
>  
> -	/* input layer checks if event is redundant */
> +	/* Send the switch event */
> +	sw_tout = button->sw_last_time +
> +		  msecs_to_jiffies(lid_report_interval);

Is it really necessary to use jiffies here?

> +	if (time_after(jiffies, sw_tout) &&
> +	    (button->sw_last_state == !!state)) {

The inner parens are not necessary.

And why not just button->sw_last_state == state?

> +		/* Send the complement switch event */
> +		input_report_switch(button->input, SW_LID, state);
> +		input_sync(button->input);
> +	}
>  	input_report_switch(button->input, SW_LID, !state);
>  	input_sync(button->input);
> +	button->sw_last_state = !!state;
> +	button->sw_last_time = jiffies;
>  
>  	if (state)
>  		pm_wakeup_event(&device->dev, 0);
> @@ -407,6 +424,8 @@ 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->sw_last_state = !!acpi_lid_evaluate_state(device);
> +		button->sw_last_time = jiffies;
>  	} else {
>  		printk(KERN_ERR PREFIX "Unsupported hid [%s]\n", hid);
>  		error = -ENODEV;
> 

Thanks,
Rafael