Re: [PATCH] backlight: pwm_bl: Fix broken PWM backlight for non-dt platforms

[Lee Jones <lee.jones@linaro.org>]

On Thu, 10 Dec 2015, Philipp Zabel wrote:

> Commit ee65ad0e2a9e ("backlight: pwm_bl: Avoid backlight flicker when
> probed from DT") tries to dereference the device of_node pointer
> unconditionally, causing a NULL pointer dereference on non-dt platforms.
> Fix it by replacing the phandle variable with a node variable and
> by checking that for NULL before dereferencing it.
> 
> Reported-by: Robert Jarzmik <robert.jarzmik@free.fr>
> Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
> ---
>  drivers/video/backlight/pwm_bl.c | 9 ++++-----
>  1 file changed, 4 insertions(+), 5 deletions(-)

Applied, thanks.

> diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c
> index 3daf9cc..a22c1ec 100644
> --- a/drivers/video/backlight/pwm_bl.c
> +++ b/drivers/video/backlight/pwm_bl.c
> @@ -198,8 +198,8 @@ static int pwm_backlight_probe(struct platform_device *pdev)
>  	struct platform_pwm_backlight_data defdata;
>  	struct backlight_properties props;
>  	struct backlight_device *bl;
> +	struct device_node *node = pdev->dev.of_node;
>  	struct pwm_bl_data *pb;
> -	phandle phandle = pdev->dev.of_node->phandle;
>  	int initial_blank = FB_BLANK_UNBLANK;
>  	int ret;
>  
> @@ -273,7 +273,7 @@ static int pwm_backlight_probe(struct platform_device *pdev)
>  		 * assume that another driver will enable the backlight at the
>  		 * appropriate time. Therefore, if it is disabled, keep it so.
>  		 */
> -		if (phandle &&
> +		if (node && node->phandle &&
>  		    gpiod_get_direction(pb->enable_gpio) == GPIOF_DIR_OUT &&
>  		    gpiod_get_value(pb->enable_gpio) == 0)
>  			initial_blank = FB_BLANK_POWERDOWN;
> @@ -287,12 +287,11 @@ static int pwm_backlight_probe(struct platform_device *pdev)
>  		goto err_alloc;
>  	}
>  
> -	if (phandle && !regulator_is_enabled(pb->power_supply))
> +	if (node && node->phandle && !regulator_is_enabled(pb->power_supply))
>  		initial_blank = FB_BLANK_POWERDOWN;
>  
>  	pb->pwm = devm_pwm_get(&pdev->dev, NULL);
> -	if (IS_ERR(pb->pwm) && PTR_ERR(pb->pwm) != -EPROBE_DEFER
> -	    && !pdev->dev.of_node) {
> +	if (IS_ERR(pb->pwm) && PTR_ERR(pb->pwm) != -EPROBE_DEFER && !node) {
>  		dev_err(&pdev->dev, "unable to request PWM, trying legacy API\n");
>  		pb->legacy = true;
>  		pb->pwm = pwm_request(data->pwm_id, "pwm-backlight");

-- 
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
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