Re: [PATCH v5 1/3] dt-bindings: leds: Add bindings for the TLC5925 controller

[Jean-Jacques Hiblot]

On 18/06/2022 01:19, Rob Herring wrote:
> On Tue, Jun 14, 2022 at 05:42:43PM +0200, Jean-Jacques Hiblot wrote:
> > Add bindings documentation for the TLC5925 LED controller.
> >
> > Signed-off-by: Jean-Jacques Hiblot <jjhiblot@xxxxxxxxxxxxxxx>
> > ---
> >   .../devicetree/bindings/leds/ti,tlc5925.yaml  | 107 ++++++++++++++++++
> >   1 file changed, 107 insertions(+)
> >   create mode 100644 Documentation/devicetree/bindings/leds/ti,tlc5925.yaml
> >
> > diff --git a/Documentation/devicetree/bindings/leds/ti,tlc5925.yaml b/Documentation/devicetree/bindings/leds/ti,tlc5925.yaml
> > new file mode 100644
> > index 000000000000..12a71e48f854
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/leds/ti,tlc5925.yaml
> > @@ -0,0 +1,107 @@
> > +# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
> > +%YAML 1.2
> > +---
> > +$id: http://devicetree.org/schemas/leds/ti,tlc5925.yaml#
> > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > +
> > +title: LEDs connected to TI TLC5925 controller
> > +
> > +maintainers:
> > +  - Jean-Jacques Hiblot <jjhiblot@xxxxxxxxxxxxxxx>
> > +
> > +description: |
> > +  The TLC5925 is a low-power 16-channel constant-current LED sink driver.
> > +  It is controlled through a SPI interface.
> > +  It is built around a shift register and latches which convert serial
> > +  input data into a parallel output. Several TLC5925 can be chained to
> > +  control more than 16 LEDs with a single chip-select.
> > +  The brightness level cannot be controlled, each LED is either on or off.
> > +
> > +  Each LED is represented as a sub-node of the ti,tlc5925 device.
> > +
> > +$ref: /schemas/spi/spi-peripheral-props.yaml#
> > +
> > +properties:
> > +  compatible:
> > +    const: ti,tlc5925
> > +
> > +  ti,shift-register-length:
> > +    $ref: /schemas/types.yaml#/definitions/uint32
> > +    minimum: 8
> > +    description: |
> Don't need '|' if no formatting to preserve.
>
> > +      The length of the shift register. If several TLC5925 are chained,
> > +      shift_register_length should be set to 16 times the number of TLC5925.
> > +      The value must be a multiple of 8.
> multipleOf: 8
>
> Though I'm confused why it's not 16.

The reason why it is 8 instead of 16, is that there exists other LEDs 
controllers that are compatible with this driver and use only a 8-bits 
shift register.

The main reason is that the granularity of the size of a SPI transfer is 
8 bits.

> > +
> > +  "#address-cells":
> > +    const: 1
> > +
> > +  "#size-cells":
> > +    const: 0
> > +
> > +  output-enable-b-gpios:
> > +    $ref: /schemas/types.yaml#/definitions/phandle-array
> Already has a type.
>
> > +    description: |
> > +      Optional GPIO pins to enable/disable the parallel output. They describe
> > +      the GPIOs connected to the OE/ pin of the TLC5925s.
> > +
> > +patternProperties:
> > +  "@[0-9a-f]+$":
> > +    type: object
> > +    $ref: common.yaml#
>         unevaluatedProperties: false
>
> > +
> > +    properties:
> > +      reg:
> > +        $ref: /schemas/types.yaml#/definitions/uint32
> Don't need a type here.
>
> > +        description: |
> > +          LED pin number (must be lower than ti,shift-register-length).
> > +          The furthest LED down the chain has the pin number 0.
> > +
> > +    required:
> > +      - reg
> > +
> > +required:
> > +  - "#address-cells"
> > +  - "#size-cells"
> > +  - ti,shift-register-length
> Is there not a default when not chained?

A default value could be used indeed. I'll rework the driver to use a 
default value of 16

Thanks

Jean-Jacques

> > +
> > +unevaluatedProperties: false
> > +
> > +examples:
> > +  - |
> > +    #include <dt-bindings/gpio/gpio.h>
> > +    #include <dt-bindings/leds/common.h>
> > +
> > +    spi0 {
> spi {
>
> > +        #address-cells = <1>;
> > +        #size-cells = <0>;
> > +
> > +        leds@2 {
> > +            compatible = "ti,tlc5925";
> > +            reg = <0x02>;
> > +            spi-max-frequency = <30000000>;
> > +            ti,shift-register-length = <32>;
> > +            output-enable-b-gpios = <&gpio0b 9 GPIO_ACTIVE_HIGH>, <&gpio0b 7 GPIO_ACTIVE_HIGH>;
> > +            #address-cells = <1>;
> > +            #size-cells = <0>;
> > +
> > +            led@0 {
> > +                reg = <0>;
> > +                function = LED_FUNCTION_STATUS;
> > +                color = <LED_COLOR_ID_GREEN>;
> > +            };
> > +
> > +            led@4 {
> > +                reg = <4>;
> > +                function = LED_FUNCTION_STATUS;
> > +                color = <LED_COLOR_ID_RED>;
> > +            };
> > +
> > +            led@1f {
> > +                reg = <31>;
> > +                function = LED_FUNCTION_PANIC;
> > +                color = <LED_COLOR_ID_RED>;
> > +            };
> > +        };
> > +
> > +    };
> > --
> > 2.25.1