linux-kernel - Re: [PATCH] video: backlight: Replace old GPIO APIs with GPIO Consumer APIs for sky81542-backlight driver

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Date:   Wed, 12 Jun 2019 11:26:15 +0100
From:   Daniel Thompson <daniel.thompson@...aro.org>
To:     Shobhit Kukreti <shobhitkukreti@...il.com>
Cc:     Lee Jones <lee.jones@...aro.org>,
        Jingoo Han <jingoohan1@...il.com>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] video: backlight: Replace old GPIO APIs with GPIO
 Consumer APIs for sky81542-backlight driver

Hi Shobhit

Thanks for the patch. Feedback below...


On Tue, Jun 11, 2019 at 09:32:32PM -0700, Shobhit Kukreti wrote:
> Port the sky81452-backlight driver to adhere to new gpio descriptor based
> APIs. Modified the file sky81452-backlight.c and sky81452-backlight.h.
> The gpio descriptor property in device tree should be "sky81452-en-gpios"

That is contradicted by the device tree bindings. The property should
remain "gpios" as it was before this conversion.


> Removed unnecessary header files "linux/gpio.h" and "linux/of_gpio.h".
> 
> Signed-off-by: Shobhit Kukreti <shobhitkukreti@...il.com>

What level of testing have you done? Is this a fix for hardware you own
or a cleanup after searching the sources?


> ---
>  drivers/video/backlight/sky81452-backlight.c     | 24 ++++++++++++------------
>  include/linux/platform_data/sky81452-backlight.h |  4 +++-
>  2 files changed, 15 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/video/backlight/sky81452-backlight.c b/drivers/video/backlight/sky81452-backlight.c
> index d414c7a..12ef628 100644
> --- a/drivers/video/backlight/sky81452-backlight.c
> +++ b/drivers/video/backlight/sky81452-backlight.c
> @@ -19,12 +19,10 @@
>  
>  #include <linux/backlight.h>
>  #include <linux/err.h>
> -#include <linux/gpio.h>
>  #include <linux/init.h>
>  #include <linux/kernel.h>
>  #include <linux/module.h>
>  #include <linux/of.h>
> -#include <linux/of_gpio.h>
>  #include <linux/platform_device.h>
>  #include <linux/regmap.h>
>  #include <linux/platform_data/sky81452-backlight.h>
> @@ -193,7 +191,6 @@ static struct sky81452_bl_platform_data *sky81452_bl_parse_dt(
>  	pdata->ignore_pwm = of_property_read_bool(np, "skyworks,ignore-pwm");
>  	pdata->dpwm_mode = of_property_read_bool(np, "skyworks,dpwm-mode");
>  	pdata->phase_shift = of_property_read_bool(np, "skyworks,phase-shift");
> -	pdata->gpio_enable = of_get_gpio(np, 0);
>  
>  	ret = of_property_count_u32_elems(np, "led-sources");
>  	if (ret < 0) {
> @@ -274,13 +271,17 @@ static int sky81452_bl_probe(struct platform_device *pdev)
>  		if (IS_ERR(pdata))
>  			return PTR_ERR(pdata);
>  	}
> -
> -	if (gpio_is_valid(pdata->gpio_enable)) {
> -		ret = devm_gpio_request_one(dev, pdata->gpio_enable,
> -					GPIOF_OUT_INIT_HIGH, "sky81452-en");
> -		if (ret < 0) {
> -			dev_err(dev, "failed to request GPIO. err=%d\n", ret);
> -			return ret;
> +	pdata->gpiod_enable = devm_gpiod_get(dev, "sk81452-en", GPIOD_OUT_HIGH);

As above... I think the second argument here needs to be NULL in order
to preserve the current DT bindings.


> +	if (IS_ERR(pdata->gpiod_enable)) {
> +		long ret = PTR_ERR(pdata->gpiod_enable);
> +
> +		/**

Nitpicking... but no second star here. That's a trigger symbold for
documentation processors.

> +		 * gpiod_enable is optional in device tree.
> +		 * Return error only if gpio was assigned in device tree

Also nitpicking but I had to read this a few times because
gpiod_enable is not in device tree, gpios is.

This is a common pattern so the comment can be very short. Something
like:

    This DT property is optional so no need to propagate ENOENT


> +		 */
> +		if (ret != -ENOENT) {
> +			dev_err(dev, "failed to request GPIO. err=%ld\n", ret);
> +			return PTR_ERR(pdata->gpiod_enable);
>  		}
>  	}
>  
> @@ -323,8 +324,7 @@ static int sky81452_bl_remove(struct platform_device *pdev)
>  	bd->props.brightness = 0;
>  	backlight_update_status(bd);
>  
> -	if (gpio_is_valid(pdata->gpio_enable))
> -		gpio_set_value_cansleep(pdata->gpio_enable, 0);
> +	gpiod_set_value_cansleep(pdata->gpiod_enable, 0);
>  
>  	return 0;
>  }
> diff --git a/include/linux/platform_data/sky81452-backlight.h b/include/linux/platform_data/sky81452-backlight.h
> index 1231e9b..dc4cb85 100644
> --- a/include/linux/platform_data/sky81452-backlight.h
> +++ b/include/linux/platform_data/sky81452-backlight.h
> @@ -20,6 +20,8 @@
>  #ifndef _SKY81452_BACKLIGHT_H
>  #define _SKY81452_BACKLIGHT_H
>  
> +#include <linux/gpio/consumer.h>
> +

This heaer file should be included from the C file... it is not required
to parse the header.


Daniel.


>  /**
>   * struct sky81452_platform_data
>   * @name:	backlight driver name.
> @@ -34,7 +36,7 @@
>   */
>  struct sky81452_bl_platform_data {
>  	const char *name;
> -	int gpio_enable;
> +	struct gpio_desc *gpiod_enable;
>  	unsigned int enable;
>  	bool ignore_pwm;
>  	bool dpwm_mode;
> -- 
> 2.7.4
>