linux-kernel - Re: [PATCH v6 1/4] dt-bindings: backlight: Add max25014 support

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [day] [month] [year] [list]
Message-ID: <20251209190722.GA945742-robh@kernel.org>
Date: Tue, 9 Dec 2025 13:07:22 -0600
From: Rob Herring <robh@...nel.org>
To: Maud Spierings <maudspierings@...ontroll.com>
Cc: Frank Li <Frank.li@....com>, Lee Jones <lee@...nel.org>,
	Daniel Thompson <danielt@...nel.org>,
	Jingoo Han <jingoohan1@...il.com>, Pavel Machek <pavel@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>, Helge Deller <deller@....de>,
	Shawn Guo <shawnguo@...nel.org>,
	Sascha Hauer <s.hauer@...gutronix.de>,
	Pengutronix Kernel Team <kernel@...gutronix.de>,
	Fabio Estevam <festevam@...il.com>,
	Liam Girdwood <lgirdwood@...il.com>,
	Mark Brown <broonie@...nel.org>, dri-devel@...ts.freedesktop.org,
	linux-leds@...r.kernel.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-fbdev@...r.kernel.org,
	imx@...ts.linux.dev, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v6 1/4] dt-bindings: backlight: Add max25014 support

On Mon, Dec 08, 2025 at 02:56:50PM +0100, Maud Spierings wrote:
> On 12/2/25 15:53, Frank Li wrote:
> > On Tue, Dec 02, 2025 at 08:46:21AM +0100, Maud Spierings wrote:
> > > On 12/1/25 17:52, Frank Li wrote:
> > > > On Mon, Dec 01, 2025 at 12:53:20PM +0100, Maud Spierings via B4 Relay wrote:
> > > > > From: Maud Spierings <maudspierings@...ontroll.com>
> > > > > 
> > > > > The Maxim MAX25014 is a 4-channel automotive grade backlight driver IC
> > > > > with integrated boost controller.
> > > > > 
> > > > > Signed-off-by: Maud Spierings <maudspierings@...ontroll.com>
> > > > > 
> > > > > ---
> > > > > 
> > > > > In the current implementation the control registers for channel 1,
> > > > > control all channels. So only one led subnode with led-sources is
> > > > > supported right now. If at some point the driver functionality is
> > > > > expanded the bindings can be easily extended with it.
> > > > > ---
> > > > >    .../bindings/leds/backlight/maxim,max25014.yaml    | 107 +++++++++++++++++++++
> > > > >    MAINTAINERS                                        |   5 +
> > > > >    2 files changed, 112 insertions(+)
> > > > > 
> > > > > diff --git a/Documentation/devicetree/bindings/leds/backlight/maxim,max25014.yaml b/Documentation/devicetree/bindings/leds/backlight/maxim,max25014.yaml
> > > > > new file mode 100644
> > > > > index 000000000000..e83723224b07
> > > > > --- /dev/null
> > > > > +++ b/Documentation/devicetree/bindings/leds/backlight/maxim,max25014.yaml
> > > > > @@ -0,0 +1,107 @@
> > > > > +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
> > > > > +%YAML 1.2
> > > > > +---
> > > > > +$id: http://devicetree.org/schemas/leds/backlight/maxim,max25014.yaml#
> > > > > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > > > > +
> > > > > +title: Maxim max25014 backlight controller
> > > > > +
> > > > > +maintainers:
> > > > > +  - Maud Spierings <maudspierings@...ontroll.com>
> > > > > +
> > > > > +properties:
> > > > > +  compatible:
> > > > > +    enum:
> > > > > +      - maxim,max25014
> > > > > +
> > > > > +  reg:
> > > > > +    maxItems: 1
> > > > > +
> > > > > +  "#address-cells":
> > > > > +    const: 1
> > > > > +
> > > > > +  "#size-cells":
> > > > > +    const: 0
> > > > > +
> > > > > +  enable-gpios:
> > > > > +    maxItems: 1
> > > > > +
> > > > > +  interrupts:
> > > > > +    maxItems: 1
> > > > > +
> > > > > +  power-supply:
> > > > > +    description: Regulator which controls the boost converter input rail.
> > > > > +
> > > > > +  pwms:
> > > > > +    maxItems: 1
> > > > > +
> > > > > +  maxim,iset:
> > > > > +    $ref: /schemas/types.yaml#/definitions/uint32
> > > > > +    maximum: 15
> > > > > +    default: 11
> > > > > +    description:
> > > > > +      Value of the ISET field in the ISET register. This controls the current
> > > > > +      scale of the outputs, a higher number means more current.
> > > > > +
> > > > > +  led@0:
> > > > 
> > > > define whole binding, allow 0-3. binding is not related with driver's
> > > > implement.
> > > > 
> > > > it'd better put unders leds.
> > > > 
> > > 
> > > so like:
> > > 
> > > backlight: backlight@6f {
> > > 	compatible = "maxim,max25014";
> > > 	reg = <0x6f>;
> > > 	enable-gpios = <&gpio1 4 GPIO_ACTIVE_HIGH>;
> > > 	pinctrl-names = "default";
> > > 	pinctrl-0 = <&pinctrl_backlight>;
> > > 	maxim,iset = <7>;
> > > 
> > > 	leds {
> > > 		#address-cells = <1>;
> > > 		#size-cells = <0>;
> > > 
> > > 		led@0 {
> > > 			reg = <0>;
> > > 			led-sources = <0 1 2>;
> > > 			default-brightness = <50>;
> > > 		};
> > > 
> > > 		optional led@.....
> > > 	};
> > > };
> > > 
> > > right?
> > 
> > yes.
> > 
> 
> I am feeling a bit weird about these led sub nodes, because it is not
> programmed as a led driver, it is programmed as a backlight. I am trying to
> figure out how this would be used later when the led strings are
> individually controllable.
> 
> it isn't possible to link the seperate strings to different displays because
> it is only one backlight device, so I don't seen any reason why it would
> ever be used in another way than what it is now, were all strings are
> programmed by one register.
> 
> The only way I can make sense of it is if instead I program this device as a
> led driver and then use the led_bl driver as the actual backlight.
> 
> Thats a pretty big step in a different direction, but then the led subnodes
> at least can be properly used I feel.

If you don't have any use for anything other than driving a single 
backlight, then I'd just drop the led nodes completely.

Rob