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Date:   Sun, 29 Oct 2023 02:11:40 +0000
From:   "dmitry.torokhov@gmail.com" <dmitry.torokhov@gmail.com>
To:     Abhishek Kumar Singh <abhi1.singh@samsung.com>
Cc:     "robh@kernel.org" <robh@kernel.org>,
        "linux-input@vger.kernel.org" <linux-input@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        SRI-N IT Security <sri-n.itsec@samsung.com>
Subject: Re: [PATCH] input: gpio-keys - optimize wakeup sequence.
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References: <CGME20231017103415epcms5p2f8f5b28a8f5d71055622b82f71b0fc93@epcms5p4>
 <899376598.3134980.1698299600677@mail-kr5-0.mail-kr5.knoxportal-kr-prod-blue.svc.cluster.local>
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Hi Abhishek,

On Thu, Oct 26, 2023 at 11:23:20AM +0530, Abhishek Kumar Singh wrote:
> Dear Mr. Dmitry,
> Greetings!
> 
> 
> The patch removes unused many APIs call chain for every suspend/resume of the device?
> if no key press event triggered.
> 
> 
> There is a call back function gpio_keys_resume() called for
> every suspend/resume of the device. and whenever this function called, it is
> reading the status of the key. And gpio_keys_resume() API further calls the
> below chain of API irrespective of key press event
> 
> 
> APIs call chain:
> static void gpio_keys_report_state(struct gpio_keys_drvdata *ddata)
> static void gpio_keys_gpio_report_event(struct gpio_button_data *bdata)
> gpiod_get_value_cansleep(bdata->gpiod);
> input_event(input, type, *bdata->code, state);
> input_sync(input);
> 
> 
> The patch avoid the above APIs call chain if there is no key press event triggered.
> It will save the device computational resources, power resources and optimize the suspend/resume time

Unfortunately it also breaks the driver as button->value does not hold
the current state of the GPIO but rather set one via device tree so that
the driver can use that value when sending EV_ABS events. So with
typical GPIO-backed keys or buttons you change results in no events
reported on resume.

I also wonder what kind of measurements you did on improvements to
suspend/resume time with your change.

Thanks.

-- 
Dmitry