linux-kernel - Re: [PATCH v2] ACPI / PM: Propagate KEY

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Date:   Fri, 29 Mar 2019 12:38:39 +0100
From:   Hans de Goede <hdegoede@...hat.com>
To:     Pavel Machek <pavel@....cz>, "Chen, Hu" <hu1.chen@...el.com>
Cc:     "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Len Brown <lenb@...nel.org>, linux-acpi@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] ACPI / PM: Propagate KEY_POWER to user space when
 resume

Hi,

On 3/29/19 11:25 AM, Pavel Machek wrote:
>> I run Android on x86 PC (it's a NUC). Everytime I press the power button
>> to wake the system, it suspends right away. After some debug, I find
>> that Android wants to see KEY_POWER at resume. Otherwise, its
>> opportunistic suspend will kick in shortly.
>>
>> However, other OS such as Ubuntu doesn't like KEY_POWER at resume. So
>> add a knob "/sys/module/button/parameters/key_power_at_resume" for users
>> to select.
>>
>> Signed-off-by: Chen, Hu <hu1.chen@...el.com>
> 
> NAK.
> 
> Fix android, lets not break kernel.

It is not that simple, as I explained in my other reply to this
patch, we alreayd have inconsistent behavior here inside the kernel.

When KEY_POWER is handled by the gpio-keys driver it does explicitly
send a KET_POWER press event when the system is woken up through the
power-button.

Arguably that is more consistent, e.g. some systems can also be woken
up through a home-button press and in that case we do want the KEY_HOMEPAGE
to be propagated to userspace after the wakeup so that we not only wake
but also switch to the homescreen (whatever that might be).

Also Android does have a good reason for wanting this, there are
many possible wakeup causes and just staying awake after wakeup is
not always the righ response. So android needs to know what is the
cause of the wakeup and the KEY_POWER event tells it the wakeup was
due to a power-button press, so the user explicitly wants the system
to wakeup.

Note I'm not saying that I'm happy with any of this, but simply NACK-ing
this patch is IMHO not the answer.

Regards,

Hans




> 
> 								Pavel
>> ---
>>
>>   drivers/acpi/button.c | 6 +++++-
>>   drivers/acpi/sleep.c  | 8 ++++++++
>>   2 files changed, 13 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/acpi/button.c b/drivers/acpi/button.c
>> index a19ff3977ac4..f98e6d85dd2b 100644
>> --- a/drivers/acpi/button.c
>> +++ b/drivers/acpi/button.c
>> @@ -129,6 +129,10 @@ struct acpi_button {
>>   	bool suspended;
>>   };
>>   
>> +/* does userspace want to see KEY_POWER at resume? */
>> +static bool key_power_at_resume __read_mostly;
>> +module_param(key_power_at_resume, bool, 0644);
>> +
>>   static BLOCKING_NOTIFIER_HEAD(acpi_lid_notifier);
>>   static struct acpi_device *lid_device;
>>   static u8 lid_init_state = ACPI_BUTTON_LID_INIT_METHOD;
>> @@ -417,7 +421,7 @@ static void acpi_button_notify(struct acpi_device *device, u32 event)
>>   			int keycode;
>>   
>>   			acpi_pm_wakeup_event(&device->dev);
>> -			if (button->suspended)
>> +			if (button->suspended && !key_power_at_resume)
>>   				break;
>>   
>>   			keycode = test_bit(KEY_SLEEP, input->keybit) ?
>> diff --git a/drivers/acpi/sleep.c b/drivers/acpi/sleep.c
>> index 403c4ff15349..c5dcee9f5872 100644
>> --- a/drivers/acpi/sleep.c
>> +++ b/drivers/acpi/sleep.c
>> @@ -462,6 +462,13 @@ static int find_powerf_dev(struct device *dev, void *data)
>>   	return !strcmp(hid, ACPI_BUTTON_HID_POWERF);
>>   }
>>   
>> +static void pwr_btn_notify(struct device *dev)
>> +{
>> +	struct acpi_device *device = to_acpi_device(dev);
>> +
>> +	device->driver->ops.notify(device, ACPI_FIXED_HARDWARE_EVENT);
>> +}
>> +
>>   /**
>>    *	acpi_pm_finish - Instruct the platform to leave a sleep state.
>>    *
>> @@ -505,6 +512,7 @@ static void acpi_pm_finish(void)
>>   				      find_powerf_dev);
>>   	if (pwr_btn_dev) {
>>   		pm_wakeup_event(pwr_btn_dev, 0);
>> +		pwr_btn_notify(pwr_btn_dev);
>>   		put_device(pwr_btn_dev);
>>   	}
>>   }
>