Re: [PATCH v1 03/22] backlight: Add get/set operations for brightness/power properties

From: daniel@ffwll.ch
Cc: Jingoo Han <jingoohan1@gmail.com>,
	Daniel Thompson <daniel.thompson@linaro.org>,
	Lee Jones <lee.jones@linaro.org>,
	dri-devel@lists.freedesktop.org,
	Daniel Vetter <daniel.vetter@ffwll.ch>
Subject: Re: [PATCH v1 03/22] backlight: Add get/set operations for brightness/power properties
Date: Tue, 4 Aug 2020 18:43:30 +0200	[thread overview]
Message-ID: <20200804164330.GL6419@phenom.ffwll.local> (raw)
In-Reply-To: <20200802110636.1018743-4-sam@ravnborg.org>

On Sun, Aug 02, 2020 at 01:06:17PM +0200, Sam Ravnborg wrote:
> Add get and set operations to incapsualte access to backlight properties.
> 
> One easy win is that the get/set operatiosn can be used when backlight
> is not included in the configuration, resulting in simpler code with
> less ifdef's and thus more readable code.
> 
> The set/get methods hides some of the confusing power states, limiting
> the power state to either ON or OFF for the drivers.
> 
> Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
> Cc: Lee Jones <lee.jones@linaro.org>
> Cc: Daniel Thompson <daniel.thompson@linaro.org>
> Cc: Jingoo Han <jingoohan1@gmail.com>
> ---
>  include/linux/backlight.h | 72 +++++++++++++++++++++++++++++++++++++++
>  1 file changed, 72 insertions(+)
> 
> diff --git a/include/linux/backlight.h b/include/linux/backlight.h
> index d683c053ec09..882ceea45ace 100644
> --- a/include/linux/backlight.h
> +++ b/include/linux/backlight.h
> @@ -474,6 +474,78 @@ static inline int backlight_get_brightness(const struct backlight_device *bd)
>  		return bd->props.brightness;
>  }
>  
> +/**
> + * backlight_get_actual_brightness - Returns the actual brightness
> + *
> + * On failure a negative error code is returned.
> + */
> +static inline int backlight_get_actual_brightness(struct backlight_device *bd)
> +{
> +	if (bd && bd->ops && bd->ops->get_brightness)
> +		return bd->ops->get_brightness(bd);
> +	else
> +		return -EINVAL;
> +}
> +
> +/**
> + * backlight_get_max_brightness - Returns maximum brightness
> + *
> + * This helper operation is preferred over direct access to
> + * &backlight_properties.max_brightness
> + *
> + * Returns 0 if backlight_device is NULL
> + */
> +
> +static inline int backlight_get_max_brightness(const struct backlight_device *bd)
> +{
> +	if (bd)
> +		return bd->props.max_brightness;
> +	else
> +		return 0;
> +}
> +
> +/**
> + * backlight_set_brightness - Set the brightness to the specified value
> + *
> + * This helper operation is preferred over direct assignment to
> + * &backlight_properties.brightness.
> + *
> + * If backlight_device is NULL then silently exit.
> + */
> +static inline void backlight_set_brightness(struct backlight_device *bd, int brightness)
> +{
> +	if (bd)
> +		bd->props.brightness = brightness;

Looking at the drivers I think including a call to backlight_update_status
would simplify a lot of code.

> +}
> +
> +/**
> + * backlight_set_power_on - Set power state to ON.
> + *
> + * This helper operation is preferred over direct assignment to
> + * backlight_properties.power.
> + *
> + * If backlight_device is NULL then silently exit.
> + */
> +static inline void backlight_set_power_on(struct backlight_device *bd)
> +{
> +	if (bd)
> +		bd->props.power = FB_BLANK_UNBLANK;
> +}
> +
> +/**
> + * backlight_set_power_off - Set power state to OFF.
> + *
> + * This helper operation is preferred over direct assignment to
> + * backlight_properties.power.
> + *
> + * If backlight_device is NULL then silently exit.
> + */
> +static inline void backlight_set_power_off(struct backlight_device *bd)

I'm not clear why we need these two above? I thought the long-term plan is
only use backlight_enable/disable and then remove the tri-state power
handling once everyone is converted over?

Or maybe I'm just confused about the goal here ...
-Daniel

> +{
> +	if (bd)
> +		bd->props.power = FB_BLANK_POWERDOWN;
> +}
> +
>  struct backlight_device *
>  backlight_device_register(const char *name, struct device *dev, void *devdata,
>  			  const struct backlight_ops *ops,
> -- 
> 2.25.1
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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