linux-kernel - Re: [PATCH 22/25] leds: convert GPIO LED trigger driver to devm

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Message-ID: <1341506716.2605.8.camel@lorien2>
Date:	Thu, 05 Jul 2012 10:45:16 -0600
From:	Shuah Khan <shuahkhan@...il.com>
To:	Bryan Wu <bryan.wu@...onical.com>
Cc:	shuahkhan@...il.com, linux-leds@...r.kernel.org, rpurdie@...ys.net,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 22/25] leds: convert GPIO LED trigger driver to
 devm_kzalloc() and cleanup error exit path

On Wed, 2012-07-04 at 13:10 +0800, Bryan Wu wrote:
> Cc: Felipe Balbi <me@...ipebalbi.com>
> Signed-off-by: Bryan Wu <bryan.wu@...onical.com>
> ---
>  drivers/leds/ledtrig-gpio.c |    8 ++------
>  1 file changed, 2 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/leds/ledtrig-gpio.c b/drivers/leds/ledtrig-gpio.c
> index ba215dc..39bd8e4 100644
> --- a/drivers/leds/ledtrig-gpio.c
> +++ b/drivers/leds/ledtrig-gpio.c
> @@ -181,13 +181,13 @@ static void gpio_trig_activate(struct led_classdev *led)
>  	struct gpio_trig_data *gpio_data;
>  	int ret;
>  
> -	gpio_data = kzalloc(sizeof(*gpio_data), GFP_KERNEL);
> +	gpio_data = devm_kzalloc(led->dev, sizeof(*gpio_data), GFP_KERNEL);
>  	if (!gpio_data)
>  		return;
>  
>  	ret = device_create_file(led->dev, &dev_attr_gpio);
>  	if (ret)
> -		goto err_gpio;
> +		return;
>  
>  	ret = device_create_file(led->dev, &dev_attr_inverted);
>  	if (ret)
> @@ -209,9 +209,6 @@ err_brightness:
>  
>  err_inverted:
>  	device_remove_file(led->dev, &dev_attr_gpio);
> -
> -err_gpio:
> -	kfree(gpio_data);
>  }
>  
>  static void gpio_trig_deactivate(struct led_classdev *led)
> @@ -225,7 +222,6 @@ static void gpio_trig_deactivate(struct led_classdev *led)
>  		flush_work(&gpio_data->work);
>  		if (gpio_data->gpio != 0)
>  			free_irq(gpio_to_irq(gpio_data->gpio), led);
> -		kfree(gpio_data);
>  		led->activated = false;
>  	}
>  }

Bryan,

I don't believe memory triggers allocate in their activate routine
should be converted to devm_kzalloc(). Based on my understanding, the
memory allocated using devm_kzalloc() us free'ed when driver is
detached. In the case of led triggers, driver stays registered while the
triggers it supports can be activated and deactivated many times. By
converting these allocations into devm_kzalloc()s could lead to memory
leaks. Please correct me if my understanding is incorrect.

If what I am saying makes sense, please take this as comment that is
applicable to all led triggers, not just this one.

Thanks,
-- Shuah



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