linux-kernel - Re: [PATCH] Input: gpio_keys_polled - always use gpiod_get_value

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Message-ID: <20161020104519.GA24289@lahna.fi.intel.com>
Date:   Thu, 20 Oct 2016 13:45:19 +0300
From:   Mika Westerberg <mika.westerberg@...ux.intel.com>
To:     Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc:     linux-input@...r.kernel.org, linux-kernel@...r.kernel.org,
        Hans de Goede <hdegoede@...hat.com>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Aaron Lu <aaron.lu@...el.com>,
        Linus Walleij <linus.walleij@...aro.org>
Subject: Re: [PATCH] Input: gpio_keys_polled - always use
 gpiod_get_value_cansleep

On Wed, Oct 19, 2016 at 04:41:07PM -0700, Dmitry Torokhov wrote:
> It does not matter if given GPIO may sleep or not when reading state,
> polling is always done in a non-atomic context, so we should always
> be able to simply use gpiod_get_value_cansleep().
> 
> Also let's note in the logs when we fail to read gpio state.
> 
> Signed-off-by: Dmitry Torokhov <dmitry.torokhov@...il.com>
> ---
>  drivers/input/keyboard/gpio_keys_polled.c | 21 ++++++++++-----------
>  1 file changed, 10 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/input/keyboard/gpio_keys_polled.c b/drivers/input/keyboard/gpio_keys_polled.c
> index daef8ea..3c79158 100644
> --- a/drivers/input/keyboard/gpio_keys_polled.c
> +++ b/drivers/input/keyboard/gpio_keys_polled.c
> @@ -34,7 +34,6 @@ struct gpio_keys_button_data {
>  	int last_state;
>  	int count;
>  	int threshold;
> -	int can_sleep;
>  };
>  
>  struct gpio_keys_polled_dev {
> @@ -76,16 +75,17 @@ static void gpio_keys_polled_check_state(struct input_polled_dev *dev,
>  {
>  	int state;
>  
> -	if (bdata->can_sleep)
> -		state = !!gpiod_get_value_cansleep(bdata->gpiod);
> -	else
> -		state = !!gpiod_get_value(bdata->gpiod);
> -
> -	gpio_keys_button_event(dev, button, state);
> +	state = gpiod_get_value_cansleep(bdata->gpiod);
> +	if (unlikely(state < 0)) {

Is this unlikely() really bringing any performance benefits here?

Otherwise this patch looks good to me (sans the below line which you
mentioned in your followup email).

> +		dev_err(input->dev.parent,
> +			"failed to get gpio state: %d\n", state);
> +	} else {
> +		gpio_keys_button_event(dev, button, state);
>  
> -	if (state != bdata->last_state) {
> -		bdata->count = 0;
> -		bdata->last_state = state;
> +		if (state != bdata->last_state) {
> +			bdata->count = 0;
> +			bdata->last_state = state;
> +		}
>  	}
>  }
>  
> @@ -341,7 +341,6 @@ static int gpio_keys_polled_probe(struct platform_device *pdev)
>  			}
>  		}
>  
> -		bdata->can_sleep = gpiod_cansleep(bdata->gpiod);
>  		bdata->last_state = -1;
>  		bdata->threshold = DIV_ROUND_UP(button->debounce_interval,
>  						pdata->poll_interval);
> -- 
> 2.8.0.rc3.226.g39d4020
> 
> 
> -- 
> Dmitry