Re: [PATCH] backlight: pm8941-wled: Add default-brightness property

[Rob Clark]

On Thu, Jul 23, 2015 at 3:52 PM, Bjorn Andersson
<bjorn.andersson@xxxxxxxxxxxxxx> wrote:
> Add the possibility of specifying the default brightness in DT.
>
> Signed-off-by: Bjorn Andersson <bjorn.andersson@xxxxxxxxxxxxxx>
> ---
>
> This depends on the patch moving pm8941-wled to backlight [1]. The dt property
> is used by several other backlight drivers, so I considered this to be a
> "common" property and it's hence not prefixed with "qcom,".
>
> [1] https://lkml.org/lkml/2015/7/21/906
>
>  Documentation/devicetree/bindings/video/backlight/pm8941-wled.txt | 1 +
>  drivers/video/backlight/pm8941-wled.c                             | 4 ++++
>  2 files changed, 5 insertions(+)
>
> diff --git a/Documentation/devicetree/bindings/video/backlight/pm8941-wled.txt b/Documentation/devicetree/bindings/video/backlight/pm8941-wled.txt
> index 424f8444a6cd..37503f8c3620 100644
> --- a/Documentation/devicetree/bindings/video/backlight/pm8941-wled.txt
> +++ b/Documentation/devicetree/bindings/video/backlight/pm8941-wled.txt
> @@ -5,6 +5,7 @@ Required properties:
>  - reg: slave address
>
>  Optional properties:
> +- default-brightness: value from: 0-4095
>  - label: The name of the backlight device
>  - qcom,cs-out: bool; enable current sink output
>  - qcom,cabc: bool; enable content adaptive backlight control
> diff --git a/drivers/video/backlight/pm8941-wled.c b/drivers/video/backlight/pm8941-wled.c
> index c704c3236034..b875e58df0fc 100644
> --- a/drivers/video/backlight/pm8941-wled.c
> +++ b/drivers/video/backlight/pm8941-wled.c
> @@ -373,6 +373,7 @@ static int pm8941_wled_probe(struct platform_device *pdev)
>         struct backlight_device *bl;
>         struct pm8941_wled *wled;
>         struct regmap *regmap;
> +       u32 val = 0;
>         int rc;

as discussed on IRC, it would be better if the default read back the
current settings (so-as to inherit bootloader splash smoothly..
drm/msm supports a memory-region phandle, for example, so it can take
over the bootloader splash-screen as stolen-mem)

and it would I think be useful to have a comment in the bindings file
explaining that you *should* use the default-brightness property to
set a sane default if bootloader isn't putting up a splash, and you
should *not* use the property if it is..

BR,
-R

>         regmap = dev_get_regmap(pdev->dev.parent, NULL);
> @@ -395,8 +396,11 @@ static int pm8941_wled_probe(struct platform_device *pdev)
>         if (rc)
>                 return rc;
>
> +       of_property_read_u32(pdev->dev.of_node, "default-brightness", &val);
> +
>         memset(&props, 0, sizeof(struct backlight_properties));
>         props.type = BACKLIGHT_RAW;
> +       props.brightness = val;
>         props.max_brightness = PM8941_WLED_REG_VAL_MAX;
>         bl = devm_backlight_device_register(&pdev->dev, wled->name,
>                                             &pdev->dev, wled,
> --
> 1.8.2.2
>
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