Re: [PATCH 1/8] dt-bindings: media: ov5640: Convert to json-schema

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

Hi Jacopo,

On Thu, Jul 16, 2020 at 09:04:33AM +0200, Jacopo Mondi wrote:
> On Thu, Jul 16, 2020 at 04:53:23AM +0300, Laurent Pinchart wrote:
> > On Wed, Jul 15, 2020 at 04:09:44PM +0200, Jacopo Mondi wrote:
> > > Convert the ov5640 bindings document to json-schema and update
> > > the MAINTAINERS file accordingly.
> > >
> > > Signed-off-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
> > > ---
> > > Hi Steve,
> > >   I've added myself as maintainer in the bindings, with your ack
> > > I would be happy to add myself as maintainer or reviewer for this driver
> > > in MAINTAINERS, as I've recently been looking after this driver, mostly
> > > for the MIPI CSI-2 interface part.
> > >
> > > ---
> > >  .../devicetree/bindings/media/i2c/ov5640.txt  |  92 ---------
> > >  .../devicetree/bindings/media/i2c/ov5640.yaml | 181 ++++++++++++++++++
> > >  MAINTAINERS                                   |   1 +
> > >  3 files changed, 182 insertions(+), 92 deletions(-)
> > >  delete mode 100644 Documentation/devicetree/bindings/media/i2c/ov5640.txt
> > >  create mode 100644 Documentation/devicetree/bindings/media/i2c/ov5640.yaml
> > >
> > > diff --git a/Documentation/devicetree/bindings/media/i2c/ov5640.txt b/Documentation/devicetree/bindings/media/i2c/ov5640.txt
> > > deleted file mode 100644
> > > index c97c2f2da12d..000000000000
> > > --- a/Documentation/devicetree/bindings/media/i2c/ov5640.txt
> > > +++ /dev/null
> > > @@ -1,92 +0,0 @@
> > > -* Omnivision OV5640 MIPI CSI-2 / parallel sensor
> > > -
> > > -Required Properties:
> > > -- compatible: should be "ovti,ov5640"
> > > -- clocks: reference to the xclk input clock.
> > > -- clock-names: should be "xclk".
> > > -- DOVDD-supply: Digital I/O voltage supply, 1.8 volts
> > > -- AVDD-supply: Analog voltage supply, 2.8 volts
> > > -- DVDD-supply: Digital core voltage supply, 1.5 volts
> > > -
> > > -Optional Properties:
> > > -- reset-gpios: reference to the GPIO connected to the reset pin, if any.
> > > -	       This is an active low signal to the OV5640.
> > > -- powerdown-gpios: reference to the GPIO connected to the powerdown pin,
> > > -		   if any. This is an active high signal to the OV5640.
> > > -- rotation: as defined in
> > > -	    Documentation/devicetree/bindings/media/video-interfaces.txt,
> > > -	    valid values are 0 (sensor mounted upright) and 180 (sensor
> > > -	    mounted upside down).
> > > -
> > > -The device node must contain one 'port' child node for its digital output
> > > -video port, in accordance with the video interface bindings defined in
> > > -Documentation/devicetree/bindings/media/video-interfaces.txt.
> > > -
> > > -OV5640 can be connected to a MIPI CSI-2 bus or a parallel bus endpoint.
> > > -
> > > -Endpoint node required properties for CSI-2 connection are:
> > > -- remote-endpoint: a phandle to the bus receiver's endpoint node.
> > > -- clock-lanes: should be set to <0> (clock lane on hardware lane 0)
> > > -- data-lanes: should be set to <1> or <1 2> (one or two CSI-2 lanes supported)
> > > -
> > > -Endpoint node required properties for parallel connection are:
> > > -- remote-endpoint: a phandle to the bus receiver's endpoint node.
> > > -- bus-width: shall be set to <8> for 8 bits parallel bus
> > > -	     or <10> for 10 bits parallel bus
> > > -- data-shift: shall be set to <2> for 8 bits parallel bus
> > > -	      (lines 9:2 are used) or <0> for 10 bits parallel bus
> > > -- hsync-active: active state of the HSYNC signal, 0/1 for LOW/HIGH respectively.
> > > -- vsync-active: active state of the VSYNC signal, 0/1 for LOW/HIGH respectively.
> > > -- pclk-sample: sample data on rising (1) or falling (0) edge of the pixel clock
> > > -	       signal.
> > > -
> > > -Examples:
> > > -
> > > -&i2c1 {
> > > -	ov5640: camera@3c {
> > > -		compatible = "ovti,ov5640";
> > > -		pinctrl-names = "default";
> > > -		pinctrl-0 = <&pinctrl_ov5640>;
> > > -		reg = <0x3c>;
> > > -		clocks = <&clks IMX6QDL_CLK_CKO>;
> > > -		clock-names = "xclk";
> > > -		DOVDD-supply = <&vgen4_reg>; /* 1.8v */
> > > -		AVDD-supply = <&vgen3_reg>;  /* 2.8v */
> > > -		DVDD-supply = <&vgen2_reg>;  /* 1.5v */
> > > -		powerdown-gpios = <&gpio1 19 GPIO_ACTIVE_HIGH>;
> > > -		reset-gpios = <&gpio1 20 GPIO_ACTIVE_LOW>;
> > > -		rotation = <180>;
> > > -
> > > -		port {
> > > -			/* MIPI CSI-2 bus endpoint */
> > > -			ov5640_to_mipi_csi2: endpoint {
> > > -				remote-endpoint = <&mipi_csi2_from_ov5640>;
> > > -				clock-lanes = <0>;
> > > -				data-lanes = <1 2>;
> > > -			};
> > > -		};
> > > -	};
> > > -};
> > > -
> > > -&i2c1 {
> > > -	ov5640: camera@3c {
> > > -		compatible = "ovti,ov5640";
> > > -		pinctrl-names = "default";
> > > -		pinctrl-0 = <&pinctrl_ov5640>;
> > > -		reg = <0x3c>;
> > > -		clocks = <&clk_ext_camera>;
> > > -		clock-names = "xclk";
> > > -
> > > -		port {
> > > -			/* Parallel bus endpoint */
> > > -			ov5640_to_parallel: endpoint {
> > > -				remote-endpoint = <&parallel_from_ov5640>;
> > > -				bus-width = <8>;
> > > -				data-shift = <2>; /* lines 9:2 are used */
> > > -				hsync-active = <0>;
> > > -				vsync-active = <0>;
> > > -				pclk-sample = <1>;
> > > -			};
> > > -		};
> > > -	};
> > > -};
> > > diff --git a/Documentation/devicetree/bindings/media/i2c/ov5640.yaml b/Documentation/devicetree/bindings/media/i2c/ov5640.yaml
> > > new file mode 100644
> > > index 000000000000..9c32262a3621
> > > --- /dev/null
> > > +++ b/Documentation/devicetree/bindings/media/i2c/ov5640.yaml
> > > @@ -0,0 +1,181 @@
> > > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> > > +%YAML 1.2
> > > +---
> > > +$id: http://devicetree.org/schemas/media/i2c/ov5640.yaml#
> > > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > > +
> > > +title: Omnivision OV5640 MIPI CSI-2 / parallel sensor
> > > +
> > > +maintainers:
> > > +  - Steve Longerbeam <slongerbeam@gmail.com>
> > > +  - Jacopo Mondi <jacopo@jmondi.org>
> > > +
> > > +description: -|
> > > +  OV5640 is a 5 megapixels image sensor capable of producing images in RBG, RAW,
> >
> > s/OV5640/The OV5640/
> > s/RBG/RGB/
> >
> 
> Ups, will fix
> 
> > > +  YUV and compressed formats. It features a MIPI CSI-2 and a parallel data
> > > +  interface and an I2C-compatible (CCI) control interface.
> > > +
> > > +properties:
> > > +  compatible:
> > > +    const: ovti,ov5640
> > > +
> > > +  reg:
> > > +    description: I2C device address
> > > +    maxItems: 1
> > > +
> > > +  clocks:
> > > +    description: Reference to the xclk input clock.
> >
> > I'd drop this, it's implied by the clock-names
> >
> > > +    maxItems: 1
> > > +
> > > +  clock-names:
> > > +    description: Should be "xclk".
> >
> > This should be replaced with
> >
> >    const: xclk
> >
> 
> Ack for both
> 
> > > +    maxItems: 1
> > > +
> > > +  DOVDD-supply:
> > > +    description: Digital I/O voltage supply, 1.8 volts.
> > > +    maxItems: 1
> > > +
> > > +  AVDD-supply:
> > > +    description: Analog voltage supply, 2.8 volts.
> > > +    maxItems: 1
> > > +
> > > +  DVDD-supply:
> > > +    description: Digital core voltage supply.
> > > +    maxItems: 1
> > > +
> > > +  reset-gpios:
> > > +    description: |
> > > +      Reference to the GPIO connected to the reset pin, if any. This is an
> > > +      active low signal to the OV5640.
> > > +    maxItems: 1
> > > +
> > > +  powerdown-gpios:
> > > +    description: |
> > > +      Reference tot he GPIO connected to the powerdown pin, if any. This is an
> > > +      active high signal to the OV5640.
> > > +    maxItems: 1
> > > +
> > > +  rotation:
> > > +    description: |
> > > +      As defined in Documentation/devicetree/bindings/media/video-interfaces.txt,
> > > +      valid values are 0 (sensor mounted upright) and 180 (sensor mounted upside
> > > +      down).
> >
> > The second sentence should be replaced with
> >   enum:
> >     - 0
> >     - 180
> >
> 
> I copied this from the existing bindings, but I was a bit skeptical in
> first place. Support being limited to 0 and 180 only is a driver
> implementation constraint, there's nothing that prevents you from
> mounting the sensor 90deg rotated. Should the supported values be
> mentioned in the bindings at all for this property ?

You're right, it doesn't belong here. My point was that constraints
should be described with rules instead of text. I'd drop the rule in a
separate patch, or at least explain it clearly in the commit message.

> > > +
> > > +  port:
> > > +    type: object
> > > +    description: |
> > > +      The device node must contain one 'port' child node for its digital output
> > > +      video port, in accordance with the video interface bindings defined in
> > > +      Documentation/devicetree/bindings/media/video-interfaces.txt.
> > > +
> > > +      OV5640 can be connected to a MIPI CSI-2 bus or a parallel bus endpoint.
> > > +
> > > +    properties:
> > > +      endpoint:
> > > +        type: object
> > > +        properties:
> > > +          remote-endpoint:
> > > +            description: A phandle to the bus receiver's endpoint node.
> > > +
> > > +          clock-lanes:
> > > +            description: Should be set to 0 (clock lane on hardware lane 0).
> >
> > The description of most of these properties should also be replaced with
> > yaml schema rules. Ideally there should also be constraints that tell
> > which properties can be specified together. For instance here's the
> > corresponding rules from the MT9M114 DT binding (not upstream yet).
> >
> >   # See ../video-interfaces.txt for more details
> >   port:
> >     type: object
> >     properties:
> >       endpoint:
> >         type: object
> >         properties:
> >           bus-type:
> >             enum: [4, 5, 6]
> 
>                ^ this
> 
> Initially I considered switching on the bus type to be able to use an
> if construct like you shown below. But that would make the property
> mandatory, something that would break old DTB. Now, I used the word
> "break" and not "break compatibility" as the driver would still
> support old DTB, as it does not enforce that property being specified.
> But it would make old DTS invalid from a dt-schema validation point of
> view. Do we care about maintaining old DTS valid with new schema ?

Not to my knowledge, no. We should of course fix the in-tree device tree
sources to add the property, but anything out of tree, especially in
binary form, can fail to validate as long as the drivers don't break
binary compatibility.

> >
> >           clock-lanes:
> >             items:
> >               - const: 0
> >
> >           data-lanes:
> >             items:
> >               - const: 1
> >
> >           bus-width:
> >             items:
> >               - const: 8
> >
> >           hsync-active:
> >             items:
> >               - const: 1
> >
> >           vsync-active:
> >             items:
> >               - const: 1
> >
> >         required:
> >           - bus-type
> >
> >         allOf:
> >           - if:
> >               properties:
> >                 bus-type:
> >                   const: 4
> >             then:
> >               properties:
> >                 bus-width: false
> >                 hsync-active: false
> >                 vsync-active: false
> >
> >           - if:
> >               properties:
> >                 bus-type:
> >                   const: 5
> >             then:
> >               properties:
> >                 clock-lanes: false
> >                 data-lanes: false
> >
> >           - if:
> >               properties:
> >                 bus-type:
> >                   const: 6
> >             then:
> >               properties:
> >                 clock-lanes: false
> >                 data-lanes: false
> >                 hsync-active: false
> >                 vsync-active: false
> >
> >         unevaluatedProperties: false
> >
> > These comments apply to other patches in this series.
> >
> > > +
> > > +          data-lanes:
> > > +            description: |
> > > +              Should be set to <1> or <1 2> (one or two CSI-2 lanes supported).
> > > +
> > > +          bus-width:
> > > +            description: |
> > > +              Shall be set to <8> for 8 bits parallel bus or <10> for 10 bits
> > > +              parallel bus.
> > > +
> > > +          data-shift:
> > > +            description: |
> > > +              Shall be set to <2> for 8 bits parallel bus (lines 9:2 are used) or
> > > +              <0> for 10 bits parallel bus.
> 
> All of these 'supported values' should be expressed with a schema, I agree.
> 
> > > +
> > > +          hsync-active:
> > > +            description: |
> > > +              Active state of the HSYNC signal, 0/1 for LOW/HIGH respectively.
> > > +
> > > +          vsync-active:
> > > +            description: |
> > > +              Active state of the VSYNC signal, 0/1 for LOW/HIGH respectively.
> > > +
> > > +          pclk-sample:
> > > +            description: |
> > > +              Sample data on rising (1) or falling (0) edge of the pixel clock
> > > +              signal.
> > > +
> > > +        required:
> > > +          - remote-endpoint
> > > +
> > > +    additionalProperties: false
> > > +
> > > +required:
> > > +  - compatible
> > > +  - reg
> > > +  - clocks
> > > +  - clock-names
> > > +  - DOVDD-supply
> > > +  - AVDD-supply
> > > +  - DVDD-supply
> > > +  - port
> > > +
> > > +examples:
> > > +  - |
> > > +    #include <dt-bindings/gpio/gpio.h>
> > > +    #include <dt-bindings/clock/imx6qdl-clock.h>
> > > +
> > > +    i2c0 {
> > > +        #address-cells = <1>;
> > > +        #size-cells = <0>;
> > > +
> > > +        camera@3c {
> > > +            compatible = "ovti,ov5640";
> > > +            reg = <0x3c>;
> > > +            clocks = <&clks IMX6QDL_CLK_CKO>;
> > > +            clock-names = "xclk";
> > > +            DOVDD-supply = <&vgen4_reg>; /* 1.8v */
> > > +            AVDD-supply = <&vgen3_reg>;  /* 2.8v */
> > > +            DVDD-supply = <&vgen2_reg>;  /* 1.5v */
> > > +            powerdown-gpios = <&gpio1 19 GPIO_ACTIVE_HIGH>;
> > > +            reset-gpios = <&gpio1 20 GPIO_ACTIVE_LOW>;
> > > +            rotation = <180>;
> > > +
> > > +            port {
> > > +                ov5640_to_mipi_csi2: endpoint {
> > > +                    remote-endpoint = <&mipi_csi2_from_ov5640>;
> > > +                    clock-lanes = <0>;
> > > +                    data-lanes = <1 2>;
> > > +                };
> > > +            };
> > > +        };
> > > +    };
> > > +
> > > +    i2c1 {
> > > +        #address-cells = <1>;
> > > +        #size-cells = <0>;
> > > +
> > > +        camera@3c {
> > > +            compatible = "ovti,ov5640";
> > > +            reg = <0x3c>;
> > > +            clocks = <&clks IMX6QDL_CLK_CKO>;
> > > +            clock-names = "xclk";
> > > +            DOVDD-supply = <&vgen4_reg>; /* 1.8v */
> > > +            AVDD-supply = <&vgen3_reg>;  /* 2.8v */
> > > +            DVDD-supply = <&vgen2_reg>;  /* 1.5v */
> > > +            powerdown-gpios = <&gpio1 19 GPIO_ACTIVE_HIGH>;
> > > +            reset-gpios = <&gpio1 20 GPIO_ACTIVE_LOW>;
> > > +            rotation = <180>;
> > > +
> > > +            port {
> > > +                ov5640_to_parallel: endpoint {
> > > +                    remote-endpoint = <&parallel_from_ov5640>;
> > > +                    bus-width = <8>;
> > > +                };
> > > +            };
> > > +        };
> > > +    };
> > > +
> > > +...
> > > diff --git a/MAINTAINERS b/MAINTAINERS
> > > index c74d25c58e1a..0160d7567ed3 100644
> > > --- a/MAINTAINERS
> > > +++ b/MAINTAINERS
> > > @@ -12605,6 +12605,7 @@ L:	linux-media@vger.kernel.org
> > >  S:	Maintained
> > >  T:	git git://linuxtv.org/media_tree.git
> > >  F:	drivers/media/i2c/ov5640.c
> > > +F:	Documentation/devicetree/bindings/media/i2c/ov5640.yaml
> > >
> > >  OMNIVISION OV5647 SENSOR DRIVER
> > >  M:	Jacopo Mondi <jacopo@jmondi.org>

-- 
Regards,

Laurent Pinchart