linux-kernel - Re: [PATCH 2/2] pwm-backlight: switch to gpiod interface

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Date:	Wed, 7 May 2014 10:18:51 +0200
From:	Thierry Reding <thierry.reding@...il.com>
To:	Alexandre Courbot <acourbot@...dia.com>
Cc:	Jingoo Han <jg1.han@...sung.com>, Bryan Wu <cooloney@...il.com>,
	Ben Dooks <ben-linux@...ff.org>,
	Kukjin Kim <kgene.kim@...sung.com>, linux-pwm@...r.kernel.org,
	linux-gpio@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] pwm-backlight: switch to gpiod interface

On Thu, Feb 27, 2014 at 02:53:34PM +0900, Alexandre Courbot wrote:
> Switch to the new gpiod interface, which allows to handle GPIO
> properties such as active low transparently and removes a whole bunch of
> code.
> 
> There are still a couple of users of this driver that rely on passing
> the enable GPIO number through platform data, so a fallback mechanism
> using a GPIO number is still available to avoid breaking them. It will
> be removed once current users have switched to the GPIO lookup tables
> provided by the gpiod interface.
> 
> Signed-off-by: Alexandre Courbot <acourbot@...dia.com>
> ---
>  drivers/video/backlight/pwm_bl.c | 72 +++++++++++++++++-----------------------
>  include/linux/pwm_backlight.h    |  5 +--
>  2 files changed, 32 insertions(+), 45 deletions(-)

I've applied this with two tiny changes, see below. Please shout if you
think that's a bad idea.

> diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c
[...]
> @@ -256,8 +238,6 @@ static int pwm_backlight_probe(struct platform_device *pdev)
[...]
> +	pb->enable_gpio = devm_gpiod_get(&pdev->dev, "enable");
> +	if (IS_ERR(pb->enable_gpio)) {
> +		ret = PTR_ERR(pb->enable_gpio);
> +		if (ret == -ENOENT) {
> +			pb->enable_gpio = NULL;
> +			ret = 0;
> +		} else {
> +			goto err_alloc;
> +		}

I dropped the ret = 0 here because all error paths set it explicitly and
the non-error path never uses it. Now all branches have a single
statement and therefore the braces can be dropped.

> +	/*
> +	 * Compatibility fallback for drivers still using the integer GPIO
> +	 * platform data. Must go away soon.
> +	 */
> +	if (pb->enable_gpio == NULL && gpio_is_valid(data->enable_gpio)) {

Changed the first condition to !pb->enable_gpio for consistency.

Thierry

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