2020-09-11 15:50:48

by Alexander Dahl

[permalink] [raw]
Subject: [PATCH v4 3/3] dt-bindings: leds: Convert pwm to yaml

The example was adapted slightly to make use of the 'function' and
'color' properties. License discussed with the original author.

Suggested-by: Jacek Anaszewski <[email protected]>
Signed-off-by: Alexander Dahl <[email protected]>
Acked-by: Jacek Anaszewski <[email protected]>
Cc: Peter Ujfalusi <[email protected]>
---

Notes:
v3 -> v4:
* added Cc to original author of the binding

v2 -> v3:
* changed license identifier to recommended one
* added Acked-by

v2:
* added this patch to series (Suggested-by: Jacek Anaszewski)

.../devicetree/bindings/leds/leds-pwm.txt | 50 -----------
.../devicetree/bindings/leds/leds-pwm.yaml | 85 +++++++++++++++++++
2 files changed, 85 insertions(+), 50 deletions(-)
delete mode 100644 Documentation/devicetree/bindings/leds/leds-pwm.txt
create mode 100644 Documentation/devicetree/bindings/leds/leds-pwm.yaml

diff --git a/Documentation/devicetree/bindings/leds/leds-pwm.txt b/Documentation/devicetree/bindings/leds/leds-pwm.txt
deleted file mode 100644
index 6c6583c35f2f..000000000000
--- a/Documentation/devicetree/bindings/leds/leds-pwm.txt
+++ /dev/null
@@ -1,50 +0,0 @@
-LED connected to PWM
-
-Required properties:
-- compatible : should be "pwm-leds".
-
-Each LED is represented as a sub-node of the pwm-leds device. Each
-node's name represents the name of the corresponding LED.
-
-LED sub-node properties:
-- pwms : PWM property to point to the PWM device (phandle)/port (id) and to
- specify the period time to be used: <&phandle id period_ns>;
-- pwm-names : (optional) Name to be used by the PWM subsystem for the PWM device
- For the pwms and pwm-names property please refer to:
- Documentation/devicetree/bindings/pwm/pwm.txt
-- max-brightness : Maximum brightness possible for the LED
-- active-low : (optional) For PWMs where the LED is wired to supply
- rather than ground.
-- label : (optional)
- see Documentation/devicetree/bindings/leds/common.txt
-- linux,default-trigger : (optional)
- see Documentation/devicetree/bindings/leds/common.txt
-
-Example:
-
-twl_pwm: pwm {
- /* provides two PWMs (id 0, 1 for PWM1 and PWM2) */
- compatible = "ti,twl6030-pwm";
- #pwm-cells = <2>;
-};
-
-twl_pwmled: pwmled {
- /* provides one PWM (id 0 for Charing indicator LED) */
- compatible = "ti,twl6030-pwmled";
- #pwm-cells = <2>;
-};
-
-pwmleds {
- compatible = "pwm-leds";
- kpad {
- label = "omap4::keypad";
- pwms = <&twl_pwm 0 7812500>;
- max-brightness = <127>;
- };
-
- charging {
- label = "omap4:green:chrg";
- pwms = <&twl_pwmled 0 7812500>;
- max-brightness = <255>;
- };
-};
diff --git a/Documentation/devicetree/bindings/leds/leds-pwm.yaml b/Documentation/devicetree/bindings/leds/leds-pwm.yaml
new file mode 100644
index 000000000000..c74867492424
--- /dev/null
+++ b/Documentation/devicetree/bindings/leds/leds-pwm.yaml
@@ -0,0 +1,85 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/leds/leds-pwm.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: LEDs connected to PWM
+
+maintainers:
+ - Pavel Machek <[email protected]>
+
+description:
+ Each LED is represented as a sub-node of the pwm-leds device. Each
+ node's name represents the name of the corresponding LED.
+
+properties:
+ compatible:
+ const: pwm-leds
+
+patternProperties:
+ "^pwm-led-([0-9a-f])$":
+ type: object
+
+ $ref: common.yaml#
+
+ properties:
+ pwms:
+ description:
+ "PWM property to point to the PWM device (phandle)/port (id)
+ and to specify the period time to be used:
+ <&phandle id period_ns>;"
+
+ pwm-names:
+ description:
+ "Name to be used by the PWM subsystem for the PWM device For
+ the pwms and pwm-names property please refer to:
+ Documentation/devicetree/bindings/pwm/pwm.txt"
+
+ max-brightness:
+ description:
+ Maximum brightness possible for the LED
+
+ active-low:
+ description:
+ For PWMs where the LED is wired to supply rather than ground.
+
+ required:
+ - pwms
+ - max-brightness
+
+examples:
+ - |
+
+ #include <dt-bindings/leds/common.h>
+
+ twl_pwm: pwm {
+ /* provides two PWMs (id 0, 1 for PWM1 and PWM2) */
+ compatible = "ti,twl6030-pwm";
+ #pwm-cells = <2>;
+ };
+
+ twl_pwmled: pwmled {
+ /* provides one PWM (id 0 for Charing indicator LED) */
+ compatible = "ti,twl6030-pwmled";
+ #pwm-cells = <2>;
+ };
+
+ pwm_leds {
+ compatible = "pwm-leds";
+
+ pwm-led-1 {
+ label = "omap4::keypad";
+ pwms = <&twl_pwm 0 7812500>;
+ max-brightness = <127>;
+ };
+
+ pwm-led-2 {
+ color = <LED_COLOR_ID_GREEN>;
+ function = LED_FUNCTION_CHARGING;
+ pwms = <&twl_pwmled 0 7812500>;
+ max-brightness = <255>;
+ };
+ };
+
+...
--
2.20.1


2020-09-15 20:41:45

by Rob Herring

[permalink] [raw]
Subject: Re: [PATCH v4 3/3] dt-bindings: leds: Convert pwm to yaml

On Fri, Sep 11, 2020 at 05:40:04PM +0200, Alexander Dahl wrote:
> The example was adapted slightly to make use of the 'function' and
> 'color' properties. License discussed with the original author.
>
> Suggested-by: Jacek Anaszewski <[email protected]>
> Signed-off-by: Alexander Dahl <[email protected]>
> Acked-by: Jacek Anaszewski <[email protected]>
> Cc: Peter Ujfalusi <[email protected]>
> ---
>
> Notes:
> v3 -> v4:
> * added Cc to original author of the binding
>
> v2 -> v3:
> * changed license identifier to recommended one
> * added Acked-by
>
> v2:
> * added this patch to series (Suggested-by: Jacek Anaszewski)
>
> .../devicetree/bindings/leds/leds-pwm.txt | 50 -----------
> .../devicetree/bindings/leds/leds-pwm.yaml | 85 +++++++++++++++++++
> 2 files changed, 85 insertions(+), 50 deletions(-)
> delete mode 100644 Documentation/devicetree/bindings/leds/leds-pwm.txt
> create mode 100644 Documentation/devicetree/bindings/leds/leds-pwm.yaml
>
> diff --git a/Documentation/devicetree/bindings/leds/leds-pwm.txt b/Documentation/devicetree/bindings/leds/leds-pwm.txt
> deleted file mode 100644
> index 6c6583c35f2f..000000000000
> --- a/Documentation/devicetree/bindings/leds/leds-pwm.txt
> +++ /dev/null
> @@ -1,50 +0,0 @@
> -LED connected to PWM
> -
> -Required properties:
> -- compatible : should be "pwm-leds".
> -
> -Each LED is represented as a sub-node of the pwm-leds device. Each
> -node's name represents the name of the corresponding LED.
> -
> -LED sub-node properties:
> -- pwms : PWM property to point to the PWM device (phandle)/port (id) and to
> - specify the period time to be used: <&phandle id period_ns>;
> -- pwm-names : (optional) Name to be used by the PWM subsystem for the PWM device
> - For the pwms and pwm-names property please refer to:
> - Documentation/devicetree/bindings/pwm/pwm.txt
> -- max-brightness : Maximum brightness possible for the LED
> -- active-low : (optional) For PWMs where the LED is wired to supply
> - rather than ground.
> -- label : (optional)
> - see Documentation/devicetree/bindings/leds/common.txt
> -- linux,default-trigger : (optional)
> - see Documentation/devicetree/bindings/leds/common.txt
> -
> -Example:
> -
> -twl_pwm: pwm {
> - /* provides two PWMs (id 0, 1 for PWM1 and PWM2) */
> - compatible = "ti,twl6030-pwm";
> - #pwm-cells = <2>;
> -};
> -
> -twl_pwmled: pwmled {
> - /* provides one PWM (id 0 for Charing indicator LED) */
> - compatible = "ti,twl6030-pwmled";
> - #pwm-cells = <2>;
> -};
> -
> -pwmleds {
> - compatible = "pwm-leds";
> - kpad {
> - label = "omap4::keypad";
> - pwms = <&twl_pwm 0 7812500>;
> - max-brightness = <127>;
> - };
> -
> - charging {
> - label = "omap4:green:chrg";
> - pwms = <&twl_pwmled 0 7812500>;
> - max-brightness = <255>;
> - };
> -};
> diff --git a/Documentation/devicetree/bindings/leds/leds-pwm.yaml b/Documentation/devicetree/bindings/leds/leds-pwm.yaml
> new file mode 100644
> index 000000000000..c74867492424
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/leds/leds-pwm.yaml
> @@ -0,0 +1,85 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/leds/leds-pwm.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: LEDs connected to PWM
> +
> +maintainers:
> + - Pavel Machek <[email protected]>
> +
> +description:
> + Each LED is represented as a sub-node of the pwm-leds device. Each
> + node's name represents the name of the corresponding LED.
> +
> +properties:
> + compatible:
> + const: pwm-leds
> +
> +patternProperties:
> + "^pwm-led-([0-9a-f])$":

'^led-([0-9a-f])' would be my preference. A bit more on that below.

What about a single child case?

> + type: object
> +
> + $ref: common.yaml#
> +
> + properties:
> + pwms:
> + description:
> + "PWM property to point to the PWM device (phandle)/port (id)
> + and to specify the period time to be used:
> + <&phandle id period_ns>;"

No need to redefine a common property.

What is needed is how many pwms? I'd assume 1 only: 'maxItems: 1'

> +
> + pwm-names:
> + description:
> + "Name to be used by the PWM subsystem for the PWM device For
> + the pwms and pwm-names property please refer to:
> + Documentation/devicetree/bindings/pwm/pwm.txt"

Same here.

> +
> + max-brightness:
> + description:
> + Maximum brightness possible for the LED

Needs a type $ref.

> +
> + active-low:
> + description:
> + For PWMs where the LED is wired to supply rather than ground.

type: boolean

> +
> + required:
> + - pwms
> + - max-brightness

additionalProperties: false

That will cause errors if child node names were not consistent (no one
checked, so they won't be). We could just allow anything, but I prefer
to move things to be consistent yet try to capture any existing pattern.

> +
> +examples:
> + - |
> +
> + #include <dt-bindings/leds/common.h>
> +
> + twl_pwm: pwm {
> + /* provides two PWMs (id 0, 1 for PWM1 and PWM2) */
> + compatible = "ti,twl6030-pwm";
> + #pwm-cells = <2>;
> + };
> +
> + twl_pwmled: pwmled {
> + /* provides one PWM (id 0 for Charing indicator LED) */
> + compatible = "ti,twl6030-pwmled";
> + #pwm-cells = <2>;
> + };
> +
> + pwm_leds {
> + compatible = "pwm-leds";
> +
> + pwm-led-1 {
> + label = "omap4::keypad";
> + pwms = <&twl_pwm 0 7812500>;
> + max-brightness = <127>;
> + };
> +
> + pwm-led-2 {
> + color = <LED_COLOR_ID_GREEN>;
> + function = LED_FUNCTION_CHARGING;
> + pwms = <&twl_pwmled 0 7812500>;
> + max-brightness = <255>;
> + };
> + };
> +
> +...
> --
> 2.20.1
>

2020-09-18 15:15:45

by Alexander Dahl

[permalink] [raw]
Subject: Re: [PATCH v4 3/3] dt-bindings: leds: Convert pwm to yaml

Hello Rob,

thanks for your feedback. I have some questions/remarks on this new yaml
binding stuff before sending v5 (which will also replace patch 1/3 with a
different approach btw).

Am Dienstag, 15. September 2020, 22:37:35 CEST schrieb Rob Herring:
> On Fri, Sep 11, 2020 at 05:40:04PM +0200, Alexander Dahl wrote:
> > The example was adapted slightly to make use of the 'function' and
> > 'color' properties. License discussed with the original author.
> >
> > Suggested-by: Jacek Anaszewski <[email protected]>
> > Signed-off-by: Alexander Dahl <[email protected]>
> > Acked-by: Jacek Anaszewski <[email protected]>
> > Cc: Peter Ujfalusi <[email protected]>
> > ---
> >
> > Notes:
> > v3 -> v4:
> > * added Cc to original author of the binding
> >
> > v2 -> v3:
> > * changed license identifier to recommended one
> > * added Acked-by
> >
> > v2:
> > * added this patch to series (Suggested-by: Jacek Anaszewski)
> >
> > .../devicetree/bindings/leds/leds-pwm.txt | 50 -----------
> > .../devicetree/bindings/leds/leds-pwm.yaml | 85 +++++++++++++++++++
> > 2 files changed, 85 insertions(+), 50 deletions(-)
> > delete mode 100644 Documentation/devicetree/bindings/leds/leds-pwm.txt
> > create mode 100644 Documentation/devicetree/bindings/leds/leds-pwm.yaml
> >
> > diff --git a/Documentation/devicetree/bindings/leds/leds-pwm.txt
> > b/Documentation/devicetree/bindings/leds/leds-pwm.txt deleted file mode
> > 100644
> > index 6c6583c35f2f..000000000000
> > --- a/Documentation/devicetree/bindings/leds/leds-pwm.txt
> > +++ /dev/null
> > @@ -1,50 +0,0 @@
> > -LED connected to PWM
> > -
> > -Required properties:
> > -- compatible : should be "pwm-leds".
> > -
> > -Each LED is represented as a sub-node of the pwm-leds device. Each
> > -node's name represents the name of the corresponding LED.
> > -
> > -LED sub-node properties:
> > -- pwms : PWM property to point to the PWM device (phandle)/port (id) and
> > to - specify the period time to be used: <&phandle id period_ns>;
> > -- pwm-names : (optional) Name to be used by the PWM subsystem for the PWM
> > device - For the pwms and pwm-names property please refer to:
> > - Documentation/devicetree/bindings/pwm/pwm.txt
> > -- max-brightness : Maximum brightness possible for the LED
> > -- active-low : (optional) For PWMs where the LED is wired to supply
> > - rather than ground.
> > -- label : (optional)
> > - see Documentation/devicetree/bindings/leds/common.txt
> > -- linux,default-trigger : (optional)
> > - see Documentation/devicetree/bindings/leds/common.txt
> > -
> > -Example:
> > -
> > -twl_pwm: pwm {
> > - /* provides two PWMs (id 0, 1 for PWM1 and PWM2) */
> > - compatible = "ti,twl6030-pwm";
> > - #pwm-cells = <2>;
> > -};
> > -
> > -twl_pwmled: pwmled {
> > - /* provides one PWM (id 0 for Charing indicator LED) */
> > - compatible = "ti,twl6030-pwmled";
> > - #pwm-cells = <2>;
> > -};
> > -
> > -pwmleds {
> > - compatible = "pwm-leds";
> > - kpad {
> > - label = "omap4::keypad";
> > - pwms = <&twl_pwm 0 7812500>;
> > - max-brightness = <127>;
> > - };
> > -
> > - charging {
> > - label = "omap4:green:chrg";
> > - pwms = <&twl_pwmled 0 7812500>;
> > - max-brightness = <255>;
> > - };
> > -};
> > diff --git a/Documentation/devicetree/bindings/leds/leds-pwm.yaml
> > b/Documentation/devicetree/bindings/leds/leds-pwm.yaml new file mode
> > 100644
> > index 000000000000..c74867492424
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/leds/leds-pwm.yaml
> > @@ -0,0 +1,85 @@
> > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> > +%YAML 1.2
> > +---
> > +$id: http://devicetree.org/schemas/leds/leds-pwm.yaml#
> > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > +
> > +title: LEDs connected to PWM
> > +
> > +maintainers:
> > + - Pavel Machek <[email protected]>
> > +
> > +description:
> > + Each LED is represented as a sub-node of the pwm-leds device. Each
> > + node's name represents the name of the corresponding LED.
> > +
> > +properties:
> > + compatible:
> > + const: pwm-leds
> > +
> > +patternProperties:
>
> > + "^pwm-led-([0-9a-f])$":
> '^led-([0-9a-f])' would be my preference. A bit more on that below.

Fine for me.

> What about a single child case?

One child or multiple childs. I found .dts files with one to four sub-nodes
of the pwm-leds device in current master.

> > + type: object
> > +
> > + $ref: common.yaml#
> > +
> > + properties:
> > + pwms:
> > + description:
> > + "PWM property to point to the PWM device (phandle)/port (id)
> > + and to specify the period time to be used:
> > + <&phandle id period_ns>;"
>
> No need to redefine a common property.

Should this look like in 'Documentation/devicetree/bindings/leds/backlight/
pwm-backlight.yaml' then?

> What is needed is how many pwms? I'd assume 1 only: 'maxItems: 1'

Yes, one pwm channel per LED.

> > +
> > + pwm-names:
> > + description:
> > + "Name to be used by the PWM subsystem for the PWM device For
> > + the pwms and pwm-names property please refer to:
> > + Documentation/devicetree/bindings/pwm/pwm.txt"
>
> Same here.
>
> > +
> > + max-brightness:
> > + description:
> > + Maximum brightness possible for the LED
>
> Needs a type $ref.

fwnode_property_read_u32() is used to read this.

>
> > +
> > + active-low:
> > + description:
> > + For PWMs where the LED is wired to supply rather than ground.
>
> type: boolean
>
> > +
> > + required:
> > + - pwms
> > + - max-brightness
>
> additionalProperties: false
>
> That will cause errors if child node names were not consistent (no one
> checked, so they won't be). We could just allow anything, but I prefer
> to move things to be consistent yet try to capture any existing pattern.

Child node names follow no scheme at all currently as far as I could see,
examples from real current .dts files:

panel, led-red, blueled, kpad, front, green, pwm_blue, ds1, network_red,
alarm-brightness, pmu_stat, overo, heartbeat, power, …

Greets
Alex

>
> > +
> > +examples:
> > + - |
> > +
> > + #include <dt-bindings/leds/common.h>
> > +
> > + twl_pwm: pwm {
> > + /* provides two PWMs (id 0, 1 for PWM1 and PWM2) */
> > + compatible = "ti,twl6030-pwm";
> > + #pwm-cells = <2>;
> > + };
> > +
> > + twl_pwmled: pwmled {
> > + /* provides one PWM (id 0 for Charing indicator LED) */
> > + compatible = "ti,twl6030-pwmled";
> > + #pwm-cells = <2>;
> > + };
> > +
> > + pwm_leds {
> > + compatible = "pwm-leds";
> > +
> > + pwm-led-1 {
> > + label = "omap4::keypad";
> > + pwms = <&twl_pwm 0 7812500>;
> > + max-brightness = <127>;
> > + };
> > +
> > + pwm-led-2 {
> > + color = <LED_COLOR_ID_GREEN>;
> > + function = LED_FUNCTION_CHARGING;
> > + pwms = <&twl_pwmled 0 7812500>;
> > + max-brightness = <255>;
> > + };
> > + };
> > +
> > +...




2020-09-18 15:38:11

by Rob Herring

[permalink] [raw]
Subject: Re: [PATCH v4 3/3] dt-bindings: leds: Convert pwm to yaml

On Fri, Sep 18, 2020 at 9:12 AM Alexander Dahl <[email protected]> wrote:
>
> Hello Rob,
>
> thanks for your feedback. I have some questions/remarks on this new yaml
> binding stuff before sending v5 (which will also replace patch 1/3 with a
> different approach btw).
>
> Am Dienstag, 15. September 2020, 22:37:35 CEST schrieb Rob Herring:
> > On Fri, Sep 11, 2020 at 05:40:04PM +0200, Alexander Dahl wrote:
> > > The example was adapted slightly to make use of the 'function' and
> > > 'color' properties. License discussed with the original author.
> > >
> > > Suggested-by: Jacek Anaszewski <[email protected]>
> > > Signed-off-by: Alexander Dahl <[email protected]>
> > > Acked-by: Jacek Anaszewski <[email protected]>
> > > Cc: Peter Ujfalusi <[email protected]>
> > > ---
> > >
> > > Notes:
> > > v3 -> v4:
> > > * added Cc to original author of the binding
> > >
> > > v2 -> v3:
> > > * changed license identifier to recommended one
> > > * added Acked-by
> > >
> > > v2:
> > > * added this patch to series (Suggested-by: Jacek Anaszewski)
> > >
> > > .../devicetree/bindings/leds/leds-pwm.txt | 50 -----------
> > > .../devicetree/bindings/leds/leds-pwm.yaml | 85 +++++++++++++++++++
> > > 2 files changed, 85 insertions(+), 50 deletions(-)
> > > delete mode 100644 Documentation/devicetree/bindings/leds/leds-pwm.txt
> > > create mode 100644 Documentation/devicetree/bindings/leds/leds-pwm.yaml
> > >
> > > diff --git a/Documentation/devicetree/bindings/leds/leds-pwm.txt
> > > b/Documentation/devicetree/bindings/leds/leds-pwm.txt deleted file mode
> > > 100644
> > > index 6c6583c35f2f..000000000000
> > > --- a/Documentation/devicetree/bindings/leds/leds-pwm.txt
> > > +++ /dev/null
> > > @@ -1,50 +0,0 @@
> > > -LED connected to PWM
> > > -
> > > -Required properties:
> > > -- compatible : should be "pwm-leds".
> > > -
> > > -Each LED is represented as a sub-node of the pwm-leds device. Each
> > > -node's name represents the name of the corresponding LED.
> > > -
> > > -LED sub-node properties:
> > > -- pwms : PWM property to point to the PWM device (phandle)/port (id) and
> > > to - specify the period time to be used: <&phandle id period_ns>;
> > > -- pwm-names : (optional) Name to be used by the PWM subsystem for the PWM
> > > device - For the pwms and pwm-names property please refer to:
> > > - Documentation/devicetree/bindings/pwm/pwm.txt
> > > -- max-brightness : Maximum brightness possible for the LED
> > > -- active-low : (optional) For PWMs where the LED is wired to supply
> > > - rather than ground.
> > > -- label : (optional)
> > > - see Documentation/devicetree/bindings/leds/common.txt
> > > -- linux,default-trigger : (optional)
> > > - see Documentation/devicetree/bindings/leds/common.txt
> > > -
> > > -Example:
> > > -
> > > -twl_pwm: pwm {
> > > - /* provides two PWMs (id 0, 1 for PWM1 and PWM2) */
> > > - compatible = "ti,twl6030-pwm";
> > > - #pwm-cells = <2>;
> > > -};
> > > -
> > > -twl_pwmled: pwmled {
> > > - /* provides one PWM (id 0 for Charing indicator LED) */
> > > - compatible = "ti,twl6030-pwmled";
> > > - #pwm-cells = <2>;
> > > -};
> > > -
> > > -pwmleds {
> > > - compatible = "pwm-leds";
> > > - kpad {
> > > - label = "omap4::keypad";
> > > - pwms = <&twl_pwm 0 7812500>;
> > > - max-brightness = <127>;
> > > - };
> > > -
> > > - charging {
> > > - label = "omap4:green:chrg";
> > > - pwms = <&twl_pwmled 0 7812500>;
> > > - max-brightness = <255>;
> > > - };
> > > -};
> > > diff --git a/Documentation/devicetree/bindings/leds/leds-pwm.yaml
> > > b/Documentation/devicetree/bindings/leds/leds-pwm.yaml new file mode
> > > 100644
> > > index 000000000000..c74867492424
> > > --- /dev/null
> > > +++ b/Documentation/devicetree/bindings/leds/leds-pwm.yaml
> > > @@ -0,0 +1,85 @@
> > > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> > > +%YAML 1.2
> > > +---
> > > +$id: http://devicetree.org/schemas/leds/leds-pwm.yaml#
> > > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > > +
> > > +title: LEDs connected to PWM
> > > +
> > > +maintainers:
> > > + - Pavel Machek <[email protected]>
> > > +
> > > +description:
> > > + Each LED is represented as a sub-node of the pwm-leds device. Each
> > > + node's name represents the name of the corresponding LED.
> > > +
> > > +properties:
> > > + compatible:
> > > + const: pwm-leds
> > > +
> > > +patternProperties:
> >
> > > + "^pwm-led-([0-9a-f])$":
> > '^led-([0-9a-f])' would be my preference. A bit more on that below.
>
> Fine for me.
>
> > What about a single child case?
>
> One child or multiple childs. I found .dts files with one to four sub-nodes
> of the pwm-leds device in current master.

For the single child case, you need to allow for just 'led' then. So
this I think: '^led(-[0-9a-f]+)?$'

> > > + type: object
> > > +
> > > + $ref: common.yaml#
> > > +
> > > + properties:
> > > + pwms:
> > > + description:
> > > + "PWM property to point to the PWM device (phandle)/port (id)
> > > + and to specify the period time to be used:
> > > + <&phandle id period_ns>;"
> >
> > No need to redefine a common property.
>
> Should this look like in 'Documentation/devicetree/bindings/leds/backlight/
> pwm-backlight.yaml' then?

Yes.

>
> > What is needed is how many pwms? I'd assume 1 only: 'maxItems: 1'
>
> Yes, one pwm channel per LED.
>
> > > +
> > > + pwm-names:
> > > + description:
> > > + "Name to be used by the PWM subsystem for the PWM device For
> > > + the pwms and pwm-names property please refer to:
> > > + Documentation/devicetree/bindings/pwm/pwm.txt"
> >
> > Same here.
> >
> > > +
> > > + max-brightness:
> > > + description:
> > > + Maximum brightness possible for the LED
> >
> > Needs a type $ref.
>
> fwnode_property_read_u32() is used to read this.

$ref: /schemas/types.yaml#/definitions/uint32

>
> >
> > > +
> > > + active-low:
> > > + description:
> > > + For PWMs where the LED is wired to supply rather than ground.
> >
> > type: boolean
> >
> > > +
> > > + required:
> > > + - pwms
> > > + - max-brightness
> >
> > additionalProperties: false
> >
> > That will cause errors if child node names were not consistent (no one
> > checked, so they won't be). We could just allow anything, but I prefer
> > to move things to be consistent yet try to capture any existing pattern.
>
> Child node names follow no scheme at all currently as far as I could see,
> examples from real current .dts files:
>
> panel, led-red, blueled, kpad, front, green, pwm_blue, ds1, network_red,
> alarm-brightness, pmu_stat, overo, heartbeat, power, …

So you can do this to allow any child node name:

additonalProperties:
type: object
$ref: common.yaml#

... everything you have under pwm-led-*

Or how gpio-keys.yaml was done also works.

Rob