linux-kernel - Re: [PATCH 1/2] ledtrig-gpio: Request user input pin as GPIO

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Date:   Fri, 17 May 2019 08:26:31 +0200
From:   Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>
To:     Kun Yi <kunyi@...gle.com>
Cc:     linux-leds@...r.kernel.org, jacek.anaszewski@...il.com,
        pavel@....cz, dmurphy@...com, linux-kernel@...r.kernel.org,
        linux-gpio@...r.kernel.org
Subject: Re: [PATCH 1/2] ledtrig-gpio: Request user input pin as GPIO

Cc: += linux-gpio@...r.kernel.org

On Thu, May 16, 2019 at 02:42:08PM -0700, Kun Yi wrote:
> The ledtrig-gpio logic assumes the input pin can be directly converted
> to IRQ using gpio_to_irq. This is problematic since there is no
> guarantee on the pinmux function nor the direction of the pin. Request
> the pin as an input GPIO before requesting it as an IRQ.

When reading this I thought the driver requested the gpio only after
converting to an irq. But in fact it didn't request and set the
direction at all.

> Tested: a free pin can be correctly requested as GPIO

This doesn't belong into the signed-off-area.

> Signed-off-by: Kun Yi <kunyi@...gle.com>
> Change-Id: I657e3e108552612506775cc348a8b4b35d40cac5

This doesn't belong into the linux history either.

> ---
>  drivers/leds/trigger/ledtrig-gpio.c | 31 +++++++++++++++++++++++------
>  1 file changed, 25 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/leds/trigger/ledtrig-gpio.c b/drivers/leds/trigger/ledtrig-gpio.c
> index ed0db8ed825f..f6d50e031492 100644
> --- a/drivers/leds/trigger/ledtrig-gpio.c
> +++ b/drivers/leds/trigger/ledtrig-gpio.c
> @@ -117,6 +117,16 @@ static ssize_t gpio_trig_gpio_show(struct device *dev,
>  	return sprintf(buf, "%u\n", gpio_data->gpio);
>  }
>  
> +static inline void free_used_gpio_if_valid(unsigned int gpio,
> +					   struct led_classdev *led)

Please stick to the function prefix used in this driver. I'd call this
function gpio_trig_free_gpio and not put "if_valid" into the name.

> +{
> +	if (gpio == 0)
> +		return;
> +
> +	free_irq(gpio_to_irq(gpio), led);
> +	gpio_free(gpio);
> +}
> +
>  static ssize_t gpio_trig_gpio_store(struct device *dev,
>  		struct device_attribute *attr, const char *buf, size_t n)
>  {
> @@ -135,20 +145,30 @@ static ssize_t gpio_trig_gpio_store(struct device *dev,
>  		return n;
>  
>  	if (!gpio) {
> -		if (gpio_data->gpio != 0)
> -			free_irq(gpio_to_irq(gpio_data->gpio), led);
> +		free_used_gpio_if_valid(gpio_data->gpio, led);
>  		gpio_data->gpio = 0;
>  		return n;
>  	}
>  
> +	ret = gpio_request(gpio, "ledtrig-gpio");
> +	if (ret) {
> +		dev_err(dev, "gpio_request failed with error %d\n", ret);
> +		return ret;
> +	}
> +
> +	ret = gpio_direction_input(gpio);
> +	if (ret) {
> +		dev_err(dev, "gpio_direction_input failed with err %d\n", ret);
> +		return ret;
> +	}

Please use gpio_request_one which implements both gpio_request() and
gpio_direction_*(). This also fixes the missing gpio_free() in the error
path of gpio_direction_input().

> +
>  	ret = request_threaded_irq(gpio_to_irq(gpio), NULL, gpio_trig_irq,
>  			IRQF_ONESHOT | IRQF_SHARED | IRQF_TRIGGER_RISING
>  			| IRQF_TRIGGER_FALLING, "ledtrig-gpio", led);
>  	if (ret) {
>  		dev_err(dev, "request_irq failed with error %d\n", ret);
>  	} else {
> -		if (gpio_data->gpio != 0)
> -			free_irq(gpio_to_irq(gpio_data->gpio), led);
> +		free_used_gpio_if_valid(gpio_data->gpio, led);
>  		gpio_data->gpio = gpio;
>  		/* After changing the GPIO, we need to update the LED. */
>  		gpio_trig_irq(0, led);
> @@ -184,8 +204,7 @@ static void gpio_trig_deactivate(struct led_classdev *led)
>  {
>  	struct gpio_trig_data *gpio_data = led_get_trigger_data(led);
>  
> -	if (gpio_data->gpio != 0)
> -		free_irq(gpio_to_irq(gpio_data->gpio), led);
> +	free_used_gpio_if_valid(gpio_data->gpio, led);
>  	kfree(gpio_data);
>  }
>  

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |