From: Daniel Thompson <daniel.thompson@linaro.org>
To: Jean-Jacques Hiblot <jjhiblot@ti.com>
Cc: jacek.anaszewski@gmail.com, pavel@ucw.cz, robh+dt@kernel.org,
mark.rutland@arm.com, lee.jones@linaro.org, jingoohan1@gmail.com,
dmurphy@ti.com, linux-leds@vger.kernel.org,
linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org,
tomi.valkeinen@ti.com
Subject: Re: [PATCH v2 3/4] dt-bindings: backlight: Add led-backlight binding
Date: Mon, 8 Jul 2019 11:50:26 +0100 [thread overview]
Message-ID: <20190708105026.jfl4krv2veb7gzow@holly.lan> (raw)
In-Reply-To: <20190708102700.23138-4-jjhiblot@ti.com>
On Mon, Jul 08, 2019 at 12:26:59PM +0200, Jean-Jacques Hiblot wrote:
> Add DT binding for led-backlight.
>
> Signed-off-by: Jean-Jacques Hiblot <jjhiblot@ti.com>
> ---
> .../bindings/leds/backlight/led-backlight.txt | 29 +++++++++++++++++++
> 1 file changed, 29 insertions(+)
> create mode 100644 Documentation/devicetree/bindings/leds/backlight/led-backlight.txt
>
> diff --git a/Documentation/devicetree/bindings/leds/backlight/led-backlight.txt b/Documentation/devicetree/bindings/leds/backlight/led-backlight.txt
> new file mode 100644
> index 000000000000..4f545316b288
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/leds/backlight/led-backlight.txt
> @@ -0,0 +1,29 @@
> +led-backlight bindings
> +
> +This binding is used to describe a basic backlight device made of LEDs.
> +It can also be used to describe a backlight device controlled by the output of
> +a LED driver.
> +
> +Required properties:
> + - compatible: "led-backlight"
> + - leds: a list of LEDs
> +
> +Optional properties:
> + - brightness-levels: Array of distinct brightness levels. These
> + are in the range from 0 to 255. The actual brightness
> + level programmed in each LED will be adjusted based on
> + its maximum brightness:
> + led brightness = (level * maximum brightness) / 255
8-bits is a narrow range and likely to make animated backlight effects
impossible because the stepping artefacts would be too obvious.
I'd rather see the brightness-levels table expressed in the native
steps of the LEDs in the leds list.
I know this means that the LEDs must have identical ranges but I think
it is OK. A backlight design whose LEDs are connected to non-identical
drivers is either badly broken or sufficiently exotic to need to special
purpose driver. The driver can therefore fail to probe if the LEDs are
mismatched.
> +
> + - default-brightness-level: The default brightness level (index into the
> + array defined by the "brightness-levels" property).
The brightness-levels property is optional... this text needs to be
updated.
Daniel.
next prev parent reply other threads:[~2019-07-08 10:50 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-08 10:26 [PATCH v2 0/4] Add a generic driver for LED-based backlight Jean-Jacques Hiblot
2019-07-08 10:26 ` Jean-Jacques Hiblot
2019-07-08 10:26 ` [PATCH v2 1/4] leds: Add of_led_get() and led_put() Jean-Jacques Hiblot
2019-07-08 10:26 ` Jean-Jacques Hiblot
2019-07-08 10:26 ` [PATCH v2 2/4] leds: Add managed API to get a LED from a device driver Jean-Jacques Hiblot
2019-07-08 10:26 ` Jean-Jacques Hiblot
2019-07-08 10:26 ` [PATCH v2 3/4] dt-bindings: backlight: Add led-backlight binding Jean-Jacques Hiblot
2019-07-08 10:26 ` Jean-Jacques Hiblot
2019-07-08 10:50 ` Daniel Thompson [this message]
2019-07-08 10:50 ` Daniel Thompson
2019-07-08 10:27 ` [PATCH v2 4/4] backlight: add led-backlight driver Jean-Jacques Hiblot
2019-07-08 10:27 ` Jean-Jacques Hiblot
2019-07-09 9:31 ` Daniel Thompson
2019-07-09 9:31 ` Daniel Thompson
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