linux-kernel - Re: [PATCH] mfd: max8925: fix dt code for backlight

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Date:	Thu, 25 Jul 2013 10:13:41 +0900
From:	Jingoo Han <jg1.han@...sung.com>
To:	'Olof Johansson' <olof@...om.net>,
	'Richard Purdie' <rpurdie@...ys.net>
Cc:	linux-kernel@...r.kernel.org, sameo@...ux.intel.com,
	'Qing Xu' <qingx@...vell.com>,
	'Haojian Zhuang' <haojian.zhuang@...il.com>,
	linux-arm-kernel@...ts.infradead.org, holt@....com,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jingoo Han <jg1.han@...sung.com>
Subject: Re: [PATCH] mfd: max8925: fix dt code for backlight

On Thursday, July 25, 2013 12:42 AM, Olof Johansson wrote:
> 
> The device-tree enablement for max8925 has several problems, but besides
> the bindings being wrong (and not having seen review) there's also some
> bad coding practices on how to fill in the platform_data from device tree.
> 
> I came across this since it causes a warning when compiling
> mmp2_defconfig, and instead of doing the minimal fix to silence the
> warning, I restructured the code a bit.
> 
> This silences the warning:
> drivers/video/backlight/max8925_bl.c: In function 'max8925_backlight_probe':
> drivers/video/backlight/max8925_bl.c:177:3: warning: statement with no effect [-Wunused-value]
> 
> Note that the bindings themselves need to be revisited too, but that will
> affect more than just the backlight driver and is best done separately;
> this just fixes the bad code for the backlight driver.
> 
> Signed-off-by: Olof Johansson <olof@...om.net>
> ---
> 
> Richard, Jingoo, this would be good to see go into 3.11 if you're
> comfortable with it.

CC'ed Andrew Morton


Hi Olof Johansson,

Currently, there is not git tree for Backlight subsystem.
I hope that this would go into 3.11 through one of other trees
with my Ack.

If not, it will go into 3.12-rc1 through mm-tree.

Acked-by: Jingoo Han <jg1.han@...sung.com>


Best regards,
Jingoo Han

> 
> 
> -Olof
> 
>  drivers/video/backlight/max8925_bl.c |   41 +++++++++++++++++-----------------
>  1 file changed, 21 insertions(+), 20 deletions(-)
> 
> diff --git a/drivers/video/backlight/max8925_bl.c b/drivers/video/backlight/max8925_bl.c
> index 5ca11b0..886e797 100644
> --- a/drivers/video/backlight/max8925_bl.c
> +++ b/drivers/video/backlight/max8925_bl.c
> @@ -101,33 +101,37 @@ static const struct backlight_ops max8925_backlight_ops = {
>  	.get_brightness	= max8925_backlight_get_brightness,
>  };
> 
> -#ifdef CONFIG_OF
> -static int max8925_backlight_dt_init(struct platform_device *pdev,
> -			      struct max8925_backlight_pdata *pdata)
> +static void max8925_backlight_dt_init(struct platform_device *pdev)
>  {
>  	struct device_node *nproot = pdev->dev.parent->of_node, *np;
> -	int dual_string;
> +	struct max8925_backlight_pdata *pdata;
> +	u32 val;
> +
> +	if (!nproot || !IS_ENABLED(CONFIG_OF))
> +		return;
> +
> +	pdata = devm_kzalloc(&pdev->dev,
> +			     sizeof(struct max8925_backlight_pdata),
> +			     GFP_KERNEL);
> +	if (!pdata)
> +		return;
> 
> -	if (!nproot)
> -		return -ENODEV;
>  	np = of_find_node_by_name(nproot, "backlight");
>  	if (!np) {
>  		dev_err(&pdev->dev, "failed to find backlight node\n");
> -		return -ENODEV;
> +		return;
>  	}
> 
> -	of_property_read_u32(np, "maxim,max8925-dual-string", &dual_string);
> -	pdata->dual_string = dual_string;
> -	return 0;
> +	if (!of_property_read_u32(np, "maxim,max8925-dual-string", &val))
> +		pdata->dual_string = val;
> +
> +	pdev->dev.platform_data = pdata;
>  }
> -#else
> -#define max8925_backlight_dt_init(x, y)	(-1)
> -#endif
> 
>  static int max8925_backlight_probe(struct platform_device *pdev)
>  {
>  	struct max8925_chip *chip = dev_get_drvdata(pdev->dev.parent);
> -	struct max8925_backlight_pdata *pdata = pdev->dev.platform_data;
> +	struct max8925_backlight_pdata *pdata;
>  	struct max8925_backlight_data *data;
>  	struct backlight_device *bl;
>  	struct backlight_properties props;
> @@ -170,13 +174,10 @@ static int max8925_backlight_probe(struct platform_device *pdev)
>  	platform_set_drvdata(pdev, bl);
> 
>  	value = 0;
> -	if (pdev->dev.parent->of_node && !pdata) {
> -		pdata = devm_kzalloc(&pdev->dev,
> -				     sizeof(struct max8925_backlight_pdata),
> -				     GFP_KERNEL);
> -		max8925_backlight_dt_init(pdev, pdata);
> -	}
> +	if (!pdev->dev.platform_data)
> +		max8925_backlight_dt_init(pdev);
> 
> +	pdata = pdev->dev.platform_data;
>  	if (pdata) {
>  		if (pdata->lxw_scl)
>  			value |= (1 << 7);
> --
> 1.7.10.4

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