Re: [PATCHv4] video: backlight: gpio-backlight: Add DT support.

[Laurent Pinchart <laurent.pinchart-ryLnwIuWjnjg/C1BVhZhaw@public.gmane.org>]

Hi Denis,

Thanks for the patch. Please see below for a couple of small comment.

On Monday 21 October 2013 11:13:33 Denis Carikli wrote:
> Cc: Richard Purdie <rpurdie-Fm38FmjxZ/leoWH0uzbU5w@public.gmane.org>
> Cc: Jingoo Han <jg1.han-Sze3O3UU22JBDgjK7y7TUQ@public.gmane.org>
> Cc: Laurent Pinchart <laurent.pinchart-ryLnwIuWjnjg/C1BVhZhaw@public.gmane.org>
> Cc: Rob Herring <rob.herring-bsGFqQB8/DxBDgjK7y7TUQ@public.gmane.org>
> Cc: Pawel Moll <pawel.moll-5wv7dgnIgG8@public.gmane.org>
> Cc: Mark Rutland <mark.rutland-5wv7dgnIgG8@public.gmane.org>
> Cc: Stephen Warren <swarren-3lzwWm7+Weoh9ZMKESR00Q@public.gmane.org>
> Cc: Ian Campbell <ijc+devicetree-KcIKpvwj1kUDXYZnReoRVg@public.gmane.org>
> Cc: devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
> Cc: Sascha Hauer <kernel-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org>
> Cc: linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org
> Cc: Lothar Waßmann <LW-bxm8fMRDkQLDiMYJYoSAnRvVK+yQ3ZXh@public.gmane.org>
> Cc: Jean-Christophe Plagniol-Villard <plagnioj-sclMFOaUSTBWk0Htik3J/w@public.gmane.org>
> Cc: Eric Bénard <eric-fO0SIAKYzcbQT0dZR+AlfA@public.gmane.org>
> Signed-off-by: Denis Carikli <denis-fO0SIAKYzcbQT0dZR+AlfA@public.gmane.org>
> ---
> ChangeLog v3->v4:
> - The default-brightness property is now optional, it defaults to 1 if not
> set. - def_value int becomes an u32.
> - gbl->def_value was set to pdata->def_value in pdata mode to avoid an extra
> check.
> ---
>  .../bindings/video/backlight/gpio-backlight.txt    |   20 ++++++
>  drivers/video/backlight/gpio_backlight.c           |   69 +++++++++++++++--
>  2 files changed, 82 insertions(+), 7 deletions(-)
>  create mode 100644
> Documentation/devicetree/bindings/video/backlight/gpio-backlight.txt
> 
> diff --git
> a/Documentation/devicetree/bindings/video/backlight/gpio-backlight.txt
> b/Documentation/devicetree/bindings/video/backlight/gpio-backlight.txt new
> file mode 100644
> index 0000000..3474d4a
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/video/backlight/gpio-backlight.txt
> @@ -0,0 +1,20 @@
> +gpio-backlight bindings
> +
> +Required properties:
> +  - compatible: "gpio-backlight"
> +  - gpios: describes the gpio that is used for enabling/disabling the
> backlight
> +     (see GPIO binding[0] for more details).
> +
> +Optional properties:
> +  - default-brightness-level: the default brightness level (can be 0(off)
> or
> +      1(on) since GPIOs only support theses levels).

I believe you should specify what the default value is when the property isn't 
available.

> +
> +[0]: Documentation/devicetree/bindings/gpio/gpio.txt
> +
> +Example:
> +
> +	backlight {
> +		compatible = "gpio-backlight";
> +		gpios = <&gpio3 4 0>;
> +		default-brightness-level = <0>;
> +	};
> diff --git a/drivers/video/backlight/gpio_backlight.c
> b/drivers/video/backlight/gpio_backlight.c index 81fb127..248124d 100644
> --- a/drivers/video/backlight/gpio_backlight.c
> +++ b/drivers/video/backlight/gpio_backlight.c
> @@ -13,6 +13,8 @@
>  #include <linux/init.h>
>  #include <linux/kernel.h>
>  #include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/of_gpio.h>
>  #include <linux/platform_data/gpio_backlight.h>
>  #include <linux/platform_device.h>
>  #include <linux/slab.h>
> @@ -23,6 +25,7 @@ struct gpio_backlight {
> 
>  	int gpio;
>  	int active;
> +	u32 def_value;
>  };
> 
>  static int gpio_backlight_update_status(struct backlight_device *bl)
> @@ -60,6 +63,41 @@ static const struct backlight_ops gpio_backlight_ops = {
>  	.check_fb	= gpio_backlight_check_fb,
>  };
> 
> +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;
> +	int ret;
> +
> +	gbl->fbdev = NULL;
> +	gbl->gpio = of_get_gpio_flags(np, 0, &gpio_flags);
> +
> +	gbl->active = (gpio_flags & OF_GPIO_ACTIVE_LOW) ? 0 : 1;

I would move this line after the error check below.

> +
> +	if (gbl->gpio == -EPROBE_DEFER) {
> +		return ERR_PTR(-EPROBE_DEFER);

Any reason not to retrun -EPROBE_DEFER directly ?

> +	} else if (gbl->gpio < 0) {
> +		dev_err(&pdev->dev, "Error: gpios is a required parameter.\n");
> +		return gbl->gpio;
> +	}

Maybe you would do something like

	if (gbl->gpio < 0) {
		if (gbl->gpio == -EPROBE_DEFER)
			dev_err(&pdev->dev, "Error: gpios is a required parameter.\n");
		return gbl->gpio;
	}

> +
> +	ret = of_property_read_u32(np, "default-brightness-level",
> +				   &gbl->def_value);
> +	if (ret < 0) {
> +		/* The property is optional. */
> +		gbl->def_value = 1;
> +	}
> +
> +	if (gbl->def_value > 1) {
> +		dev_warn(&pdev->dev,
> +			"Warning: Invalid default-brightness-level value. Its value can 
be
> either 0(off) or 1(on).\n");

I believe a less verbose message (without the second sentence) would have 
done, but that's up to you.

> +		gbl->def_value = 1;
> +	}
> +
> +	return 0;
> +}
> +
>  static int gpio_backlight_probe(struct platform_device *pdev)
>  {
>  	struct gpio_backlight_platform_data *pdata =
> @@ -67,10 +105,12 @@ static int gpio_backlight_probe(struct platform_device
> *pdev) struct backlight_properties props;
>  	struct backlight_device *bl;
>  	struct gpio_backlight *gbl;
> +	struct device_node *np = pdev->dev.of_node;
>  	int ret;
> 
> -	if (!pdata) {
> -		dev_err(&pdev->dev, "failed to find platform data\n");
> +	if (!pdata && !np) {
> +		dev_err(&pdev->dev,
> +			"failed to find platform data or device tree node.\n");
>  		return -ENODEV;
>  	}
> 
> @@ -79,14 +119,22 @@ static int gpio_backlight_probe(struct platform_device
> *pdev) return -ENOMEM;
> 
>  	gbl->dev = &pdev->dev;
> -	gbl->fbdev = pdata->fbdev;
> -	gbl->gpio = pdata->gpio;
> -	gbl->active = pdata->active_low ? 0 : 1;
> +
> +	if (np) {
> +		ret = gpio_backlight_probe_dt(pdev, gbl);
> +		if (ret)
> +			return ret;
> +	} else {
> +		gbl->fbdev = pdata->fbdev;
> +		gbl->gpio = pdata->gpio;
> +		gbl->active = pdata->active_low ? 0 : 1;
> +		gbl->def_value = pdata->def_value;
> +	}
> 
>  	ret = devm_gpio_request_one(gbl->dev, gbl->gpio, GPIOF_DIR_OUT |
>  				    (gbl->active ? GPIOF_INIT_LOW
> 
>  						 : GPIOF_INIT_HIGH),
> 
> -				    pdata->name);
> +				    pdata ? pdata->name : "backlight");
>  	if (ret < 0) {
>  		dev_err(&pdev->dev, "unable to request GPIO\n");
>  		return ret;
> @@ -103,17 +151,24 @@ static int gpio_backlight_probe(struct platform_device
> *pdev) return PTR_ERR(bl);
>  	}
> 
> -	bl->props.brightness = pdata->def_value;
> +	bl->props.brightness = gbl->def_value;
> +
>  	backlight_update_status(bl);
> 
>  	platform_set_drvdata(pdev, bl);
>  	return 0;
>  }
> 
> +static struct of_device_id gpio_backlight_of_match[] = {
> +	{ .compatible = "gpio-backlight" },
> +	{ /* sentinel */ }
> +};
> +
>  static struct platform_driver gpio_backlight_driver = {
>  	.driver		= {
>  		.name		= "gpio-backlight",
>  		.owner		= THIS_MODULE,
> +		.of_match_table = of_match_ptr(gpio_backlight_of_match),
>  	},
>  	.probe		= gpio_backlight_probe,
>  };
-- 
Regards,

Laurent Pinchart

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