Re: [PATCH 1/2] backlight: gpio: Convert to use GPIO descriptor

[Daniel Thompson]

On 30/04/17 09:17, Linus Walleij wrote:
> This driver is predominantly used by device tree systems, all
> of which can deal with modern GPIO descriptors. The legacy
> GPIO API is only used by one SH board so make the GPIO
> descriptor the default way to deal with it.

Every time I've reviewed previously I kind of got tripped up here and 
decided to defer the review "until I had more time". I've since realized 
I should probably just trust you on this bit and read the backlight code 
instead ;-).


> As an intended side effect we do not need to look around in
> the device tree for the inversion flag since the GPIO
> descriptors will intrinsically deal with this.
>
> Signed-off-by: Linus Walleij <linus.walleij@xxxxxxxxxx>

Only a tiny, tiny nit from me and, with that change:
Acked-by: Daniel Thompson <daniel.thompson@xxxxxxxxxx>


> ---
>   drivers/video/backlight/gpio_backlight.c | 74 ++++++++++++++++++++------------
>   1 file changed, 46 insertions(+), 28 deletions(-)
>
> diff --git a/drivers/video/backlight/gpio_backlight.c b/drivers/video/backlight/gpio_backlight.c
> index 18134416b154..17dd8071ad4d 100644
> --- a/drivers/video/backlight/gpio_backlight.c
> +++ b/drivers/video/backlight/gpio_backlight.c
> @@ -9,7 +9,8 @@
>   #include <linux/backlight.h>
>   #include <linux/err.h>
>   #include <linux/fb.h>
> -#include <linux/gpio.h>
> +#include <linux/gpio.h> /* Only for legacy support */
> +#include <linux/gpio/consumer.h>
>   #include <linux/init.h>
>   #include <linux/kernel.h>
>   #include <linux/module.h>
> @@ -23,7 +24,7 @@ struct gpio_backlight {
>   	struct device *dev;
>   	struct device *fbdev;
>   
> -	int gpio;
> +	struct gpio_desc *gpiod;
>   	int active;
>   	int def_value;
>   };
> @@ -38,8 +39,8 @@ static int gpio_backlight_update_status(struct backlight_device *bl)
>   	    bl->props.state & (BL_CORE_SUSPENDED | BL_CORE_FBBLANK))
>   		brightness = 0;
>   
> -	gpio_set_value_cansleep(gbl->gpio,
> -				brightness ? gbl->active : !gbl->active);
> +	gpiod_set_value_cansleep(gbl->gpiod,
> +				 brightness ? gbl->active : !gbl->active);
>   
>   	return 0;
>   }
> @@ -61,23 +62,30 @@ static const struct backlight_ops gpio_backlight_ops = {
>   static int gpio_backlight_probe_dt(struct platform_device *pdev,
>   				   struct gpio_backlight *gbl)
>   {
> -	struct device_node *np = pdev->dev.of_node;
> -	enum of_gpio_flags gpio_flags;
> +	struct device *dev = &pdev->dev;
> +	struct device_node *np = dev->of_node;
> +	enum gpiod_flags flags;
> +	int ret;
> +
> +	gbl->def_value = of_property_read_bool(np, "default-on");
> +	if (gbl->def_value)
> +		flags = GPIOD_OUT_HIGH;
> +	else
> +		flags = GPIOD_OUT_LOW;

Would prefer ternary here (like other flags assignments)...


> +	/* GPIO descriptors keep track of inversion */
> +	gbl->active = 1;
>   
> -	gbl->gpio = of_get_gpio_flags(np, 0, &gpio_flags);
> +	gbl->gpiod = devm_gpiod_get(dev, NULL, flags);
> +	if (IS_ERR(gbl->gpiod)) {
> +		ret = PTR_ERR(gbl->gpiod);
>   
> -	if (!gpio_is_valid(gbl->gpio)) {
> -		if (gbl->gpio != -EPROBE_DEFER) {
> -			dev_err(&pdev->dev,
> +		if (ret != -EPROBE_DEFER) {
> +			dev_err(dev,
>   				"Error: The gpios parameter is missing or invalid.\n");
>   		}
> -		return gbl->gpio;
> +		return ret;
>   	}
>   
> -	gbl->active = (gpio_flags & OF_GPIO_ACTIVE_LOW) ? 0 : 1;
> -
> -	gbl->def_value = of_property_read_bool(np, "default-on");
> -
>   	return 0;
>   }
>   
> @@ -89,7 +97,6 @@ static int gpio_backlight_probe(struct platform_device *pdev)
>   	struct backlight_device *bl;
>   	struct gpio_backlight *gbl;
>   	struct device_node *np = pdev->dev.of_node;
> -	unsigned long flags = GPIOF_DIR_OUT;
>   	int ret;
>   
>   	if (!pdata && !np) {
> @@ -109,22 +116,33 @@ static int gpio_backlight_probe(struct platform_device *pdev)
>   		if (ret)
>   			return ret;
>   	} else {
> +		/*
> +		 * Legacy platform data GPIO retrieveal. Do not expand
> +		 * the use of this code path, currently only used by one
> +		 * SH board.
> +		 */
> +		unsigned long flags = GPIOF_DIR_OUT;
> +
>   		gbl->fbdev = pdata->fbdev;
> -		gbl->gpio = pdata->gpio;
>   		gbl->active = pdata->active_low ? 0 : 1;
>   		gbl->def_value = pdata->def_value;
> -	}
> -
> -	if (gbl->active)
> -		flags |= gbl->def_value ? GPIOF_INIT_HIGH : GPIOF_INIT_LOW;
> -	else
> -		flags |= gbl->def_value ? GPIOF_INIT_LOW : GPIOF_INIT_HIGH;
>   
> -	ret = devm_gpio_request_one(gbl->dev, gbl->gpio, flags,
> -				    pdata ? pdata->name : "backlight");
> -	if (ret < 0) {
> -		dev_err(&pdev->dev, "unable to request GPIO\n");
> -		return ret;
> +		if (gbl->active)
> +			flags |= gbl->def_value ?
> +				GPIOF_INIT_HIGH : GPIOF_INIT_LOW;
> +		else
> +			flags |= gbl->def_value ?
> +				GPIOF_INIT_LOW : GPIOF_INIT_HIGH;
> +
> +		ret = devm_gpio_request_one(gbl->dev, pdata->gpio, flags,
> +					    pdata ? pdata->name : "backlight");
> +		if (ret < 0) {
> +			dev_err(&pdev->dev, "unable to request GPIO\n");
> +			return ret;
> +		}
> +		gbl->gpiod = gpio_to_desc(pdata->gpio);
> +		if (!gbl->gpiod)
> +			return -EINVAL;
>   	}
>   
>   	memset(&props, 0, sizeof(props));