[PATCH v1 0/3] dt-bindings: convert timing + panel-dpi to DT schema

[PATCH v1 0/3] dt-bindings: convert timing + panel-dpi to DT schema

[Sam Ravnborg]

This set of patches convert display-timing.txt to DT schema.
To do that add a panel-timing.yaml file that include all the
panel-timing properties and use this in panel-common and in display-timings.

panel-dpi was also converted so we have no .txt users left of panel-timing
in panel/

Everything passed dt_binding_check - and the trivial errors I tried in
the examples was all catched during validation.

This work was triggered by a patch-set from Oleksandr Suvorov aiming
at updating panel-lvds to support panel-dpi too.
This will make it simple to add additional properties to panel-dpi.

The .yaml file are all (GPL-2.0-only OR BSD-2-Clause).
There are some parts copied or inspired from other files,
but there is also a lot of content written by me.

The license can be questioned - and I just used
the default for new bindings.

Feedback welcome!

	Sam

Sam Ravnborg (3):
      dt-bindings: display: add panel-timing.yaml
      dt-bindings: display: convert display-timings to DT schema
      dt-bindings: display: convert panel-dpi to DT schema

 .../bindings/display/panel/display-timing.txt      | 124 +---------
 .../bindings/display/panel/display-timings.yaml    |  67 ++++++
 .../bindings/display/panel/panel-common.yaml       |   7 +-
 .../bindings/display/panel/panel-dpi.txt           |  50 ----
 .../bindings/display/panel/panel-dpi.yaml          |  71 ++++++
 .../bindings/display/panel/panel-timing.yaml       | 253 +++++++++++++++++++++
 6 files changed, 395 insertions(+), 177 deletions(-)

[PATCH v1 1/3] dt-bindings: display: add panel-timing.yaml

[Sam Ravnborg]

Add meta-schema variant of panel-timing and
reference it from panel-common.yaml.

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: Rob Herring <robh@kernel.org>
Cc: Thierry Reding <thierry.reding@gmail.com>
Cc: Oleksandr Suvorov <oleksandr.suvorov@toradex.com>
Cc: devicetree@vger.kernel.org
---
 .../bindings/display/panel/panel-common.yaml  |   7 +-
 .../bindings/display/panel/panel-timing.yaml  | 253 ++++++++++++++++++
 2 files changed, 256 insertions(+), 4 deletions(-)
 create mode 100644 Documentation/devicetree/bindings/display/panel/panel-timing.yaml

diff --git a/Documentation/devicetree/bindings/display/panel/panel-common.yaml b/Documentation/devicetree/bindings/display/panel/panel-common.yaml
index ef8d8cdfcede..8070c439adbd 100644
--- a/Documentation/devicetree/bindings/display/panel/panel-common.yaml
+++ b/Documentation/devicetree/bindings/display/panel/panel-common.yaml
@@ -54,13 +54,12 @@ properties:
 
   # Display Timings
   panel-timing:
-    type: object
     description:
       Most display panels are restricted to a single resolution and
       require specific display timings. The panel-timing subnode expresses those
-      timings as specified in the timing subnode section of the display timing
-      bindings defined in
-      Documentation/devicetree/bindings/display/panel/display-timing.txt.
+      timings.
+    allOf:
+      - $ref: panel-timing.yaml#
 
   # Connectivity
   port:
diff --git a/Documentation/devicetree/bindings/display/panel/panel-timing.yaml b/Documentation/devicetree/bindings/display/panel/panel-timing.yaml
new file mode 100644
index 000000000000..59891c7a58ee
--- /dev/null
+++ b/Documentation/devicetree/bindings/display/panel/panel-timing.yaml
@@ -0,0 +1,253 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/display/panel/panel-timing.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: panel timing bindings
+
+maintainers:
+  - Thierry Reding <thierry.reding@gmail.com>
+  - Sam Ravnborg <sam@ravnborg.org>
+
+description: |
+  There are different ways of describing the timing data data of a panel. The
+  devicetree representation corresponds to the one commonly found in datasheets
+  for panels. If a panel supports multiple signal timings, the native-mode
+  can be specified.
+
+  The parameters are defined as seen in the following illustration.
+
+  +----------+-------------------------------------+----------+-------+
+  |          |        ^                            |          |       |
+  |          |        |vback_porch                 |          |       |
+  |          |        v                            |          |       |
+  +----------#######################################----------+-------+
+  |          #        ^                            #          |       |
+  |          #        |                            #          |       |
+  |  hback   #        |                            #  hfront  | hsync |
+  |   porch  #        |       hactive              #  porch   |  len  |
+  |<-------->#<-------+--------------------------->#<-------->|<----->|
+  |          #        |                            #          |       |
+  |          #        |vactive                     #          |       |
+  |          #        |                            #          |       |
+  |          #        v                            #          |       |
+  +----------#######################################----------+-------+
+  |          |        ^                            |          |       |
+  |          |        |vfront_porch                |          |       |
+  |          |        v                            |          |       |
+  +----------+-------------------------------------+----------+-------+
+  |          |        ^                            |          |       |
+  |          |        |vsync_len                   |          |       |
+  |          |        v                            |          |       |
+  +----------+-------------------------------------+----------+-------+
+
+
+  The following is the panel timings shown with time on the x-axis.
+  This matches the timing diagrams often found in data sheets.
+
+              Active                 Front           Sync           Back
+              Region                 Porch                          Porch
+  <-----------------------><----------------><-------------><-------------->
+    //////////////////////|
+   ////////////////////// |
+  //////////////////////  |..................               ................
+                                             _______________
+
+  Timing can be specified either as a typical value or as a tuple
+  of min, typ, max values.
+
+properties:
+
+  clock-frequency:
+   $ref: /schemas/types.yaml#/definitions/uint32
+   description: |
+     Panel clock in Hz
+
+  hactive:
+    $ref: /schemas/types.yaml#/definitions/uint32
+    description: |
+       Horizontal panel resolution in pixels
+
+  vactive:
+    $ref: /schemas/types.yaml#/definitions/uint32
+    description: |
+      Verical panel resolution in pixels
+
+  hfront-porch:
+    description: |
+      Horizontal front porch panel timing
+    oneOf:
+      - allOf:
+        - $ref: /schemas/types.yaml#/definitions/uint32-array
+        - maxItems: 1
+          items:
+            description: typical number of pixels
+      - allOf:
+        - $ref: /schemas/types.yaml#/definitions/uint32-array
+        - minItems: 3
+          maxItems: 3
+          items:
+            description: min, typ, max number of pixels
+
+  hback-porch:
+    description: |
+      Horizontal back porch timing
+    oneOf:
+      - allOf:
+        - $ref: /schemas/types.yaml#/definitions/uint32-array
+        - maxItems: 1
+          items:
+            description: typical number of pixels
+      - allOf:
+        - $ref: /schemas/types.yaml#/definitions/uint32-array
+        - minItems: 3
+          maxItems: 3
+          items:
+            description: min, typ, max number of pixels
+
+  hsync-len:
+    description: |
+      Horizontal sync length panel timing
+    oneOf:
+      - allOf:
+        - $ref: /schemas/types.yaml#/definitions/uint32-array
+        - maxItems: 1
+          items:
+            description: typical number of pixels
+      - allOf:
+        - $ref: /schemas/types.yaml#/definitions/uint32-array
+        - minItems: 3
+          maxItems: 3
+          items:
+            description: min, typ, max number of pixels
+
+  vfront-porch:
+    description: |
+      Vertical front porch panel timing
+    oneOf:
+      - allOf:
+        - $ref: /schemas/types.yaml#/definitions/uint32-array
+        - maxItems: 1
+          items:
+            description: typical number of lines
+      - allOf:
+        - $ref: /schemas/types.yaml#/definitions/uint32-array
+        - minItems: 3
+          maxItems: 3
+          items:
+            description: min, typ, max number of lines
+
+  vback-porch:
+    description: |
+      Vertical back porch panel timing
+    oneOf:
+      - allOf:
+        - $ref: /schemas/types.yaml#/definitions/uint32-array
+        - maxItems: 1
+          items:
+            description: typical number of lines
+      - allOf:
+        - $ref: /schemas/types.yaml#/definitions/uint32-array
+        - minItems: 3
+          maxItems: 3
+          items:
+            description: min, typ, max number of lines
+
+  vsync-len:
+    description: |
+      Vertical sync length panel timing
+    oneOf:
+      - allOf:
+        - $ref: /schemas/types.yaml#/definitions/uint32-array
+        - maxItems: 1
+          items:
+            description: typical number of lines
+      - allOf:
+        - $ref: /schemas/types.yaml#/definitions/uint32-array
+        - minItems: 3
+          maxItems: 3
+          items:
+            description: min, typ, max number of lines
+
+  hsync-active:
+    description: |
+      Horizontal sync pulse.
+      If omitted then it is not used by the hardware
+    oneOf:
+      - const: 0
+        description: active low
+      - const: 1
+        description: active high
+
+  vsync-active:
+    description: |
+      Vertical sync pulse.
+      If omitted then it is not used by the hardware
+    oneOf:
+      - const: 0
+        description: active low
+      - const: 1
+        description: active high
+
+  de-active:
+    description: |
+      Data enable.
+      If omitted then it is not used by the hardware
+    oneOf:
+      - const: 0
+        description: active low
+      - const: 1
+        description: active high
+
+  pixelclk-active:
+    description: |
+      Data driving on rising or falling edge
+    oneOf:
+      - const: 0
+        description: |
+          Drive pixel data on falling edge and
+          sample data on rising edge
+      - const: 1
+        description: |
+          Drive pixel data on rising edge and
+          sample data on falling edge
+
+  syncclk-active:
+    description: |
+      Drive sync on rising or sample sync on falling edge.
+      If not specified then the same as pixelclk-active
+    oneOf:
+      - const: 0
+        description: |
+          Drive sync on falling edge and
+          sample sync on rising edge of pixel clock
+      - const: 1
+        description: |
+          Drive sync on rising edge and
+          sample sync on falling edge of pixel clock
+
+  interlaced:
+    type: boolean
+    description: Enable interlaced mode
+
+  doublescan:
+    type: boolean
+    description: Enable double scan mode
+
+  doubleclk:
+    type: boolean
+    description: Enable double clock mode
+
+required:
+ - clock-frequency
+ - hactive
+ - vactive
+ - hfront-porch
+ - hback-porch
+ - hsync-len
+ - vfront-porch
+ - vback-porch
+ - vsync-len
+
+additionalProperties: false
-- 
2.20.1

Re: [PATCH v1 1/3] dt-bindings: display: add panel-timing.yaml

[Oleksandr Suvorov]

On Mon, Jan 20, 2020 at 10:07 PM Sam Ravnborg <sam@ravnborg.org> wrote:
>
> Add meta-schema variant of panel-timing and
> reference it from panel-common.yaml.
>
> Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
> ---
>

There some typos:

> diff --git a/Documentation/devicetree/bindings/display/panel/panel-timing.yaml b/Documentation/devicetree/bindings/display/panel/panel-timing.yaml
> new file mode 100644
> index 000000000000..59891c7a58ee
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/display/panel/panel-timing.yaml
> @@ -0,0 +1,253 @@
...
> +description: |
> +  There are different ways of describing the timing data data of a panel. The
-----------------------------------------------------------------------^^^^^^^^^
s/data data/data/

...
> +  vactive:
> +    $ref: /schemas/types.yaml#/definitions/uint32
> +    description: |
> +      Verical panel resolution in pixels
---------^^^^^^
Vertical

Anyway, those are minor issues, so

Reviewed-by: Oleksandr Suvorov <oleksandr.suvorov@toradex.com>

> _______________________________________________
> dri-devel mailing list
> dri-devel@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/dri-devel

--
Best regards
Oleksandr Suvorov

Toradex AG
Altsagenstrasse 5 | 6048 Horw/Luzern | Switzerland | T: +41 41 500
4800 (main line)

Re: [PATCH v1 1/3] dt-bindings: display: add panel-timing.yaml

[Sam Ravnborg]

Hi Oleksandr.

> 
> There some typos:
> 
> > diff --git a/Documentation/devicetree/bindings/display/panel/panel-timing.yaml b/Documentation/devicetree/bindings/display/panel/panel-timing.yaml
> > new file mode 100644
> > index 000000000000..59891c7a58ee
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/display/panel/panel-timing.yaml
> > @@ -0,0 +1,253 @@
> ...
> > +description: |
> > +  There are different ways of describing the timing data data of a panel. The
> -----------------------------------------------------------------------^^^^^^^^^
> s/data data/data/
> 
> ...
> > +  vactive:
> > +    $ref: /schemas/types.yaml#/definitions/uint32
> > +    description: |
> > +      Verical panel resolution in pixels
> ---------^^^^^^
> Vertical

Fixed in v2 - thanks.

> 
> Anyway, those are minor issues, so
> 
> Reviewed-by: Oleksandr Suvorov <oleksandr.suvorov@toradex.com>

	Sam

Re: [PATCH v1 1/3] dt-bindings: display: add panel-timing.yaml

[Sam Ravnborg]

Hi Oleksandr

Thanks for the feedback on the typos.

> 
> Anyway, those are minor issues, so
> 
> Reviewed-by: Oleksandr Suvorov <oleksandr.suvorov@toradex.com>

I did a number of other changes so I dropped this r-b,
as you really did not review the v2 version.
v2 coming later today.

	Sam

Re: [PATCH v1 1/3] dt-bindings: display: add panel-timing.yaml

[Maxime Ripard]

Hi,

On Mon, Jan 20, 2020 at 09:06:39PM +0100, Sam Ravnborg wrote:
> Add meta-schema variant of panel-timing and
> reference it from panel-common.yaml.
>
> Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
> Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> Cc: Rob Herring <robh@kernel.org>
> Cc: Thierry Reding <thierry.reding@gmail.com>
> Cc: Oleksandr Suvorov <oleksandr.suvorov@toradex.com>
> Cc: devicetree@vger.kernel.org
> ---
>  .../bindings/display/panel/panel-common.yaml  |   7 +-
>  .../bindings/display/panel/panel-timing.yaml  | 253 ++++++++++++++++++
>  2 files changed, 256 insertions(+), 4 deletions(-)
>  create mode 100644 Documentation/devicetree/bindings/display/panel/panel-timing.yaml
>
> diff --git a/Documentation/devicetree/bindings/display/panel/panel-common.yaml b/Documentation/devicetree/bindings/display/panel/panel-common.yaml
> index ef8d8cdfcede..8070c439adbd 100644
> --- a/Documentation/devicetree/bindings/display/panel/panel-common.yaml
> +++ b/Documentation/devicetree/bindings/display/panel/panel-common.yaml
> @@ -54,13 +54,12 @@ properties:
>
>    # Display Timings
>    panel-timing:
> -    type: object
>      description:
>        Most display panels are restricted to a single resolution and
>        require specific display timings. The panel-timing subnode expresses those
> -      timings as specified in the timing subnode section of the display timing
> -      bindings defined in
> -      Documentation/devicetree/bindings/display/panel/display-timing.txt.
> +      timings.
> +    allOf:
> +      - $ref: panel-timing.yaml#
>
>    # Connectivity
>    port:
> diff --git a/Documentation/devicetree/bindings/display/panel/panel-timing.yaml b/Documentation/devicetree/bindings/display/panel/panel-timing.yaml
> new file mode 100644
> index 000000000000..59891c7a58ee
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/display/panel/panel-timing.yaml
> @@ -0,0 +1,253 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/display/panel/panel-timing.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: panel timing bindings
> +
> +maintainers:
> +  - Thierry Reding <thierry.reding@gmail.com>
> +  - Sam Ravnborg <sam@ravnborg.org>
> +
> +description: |
> +  There are different ways of describing the timing data data of a panel. The
> +  devicetree representation corresponds to the one commonly found in datasheets
> +  for panels. If a panel supports multiple signal timings, the native-mode
> +  can be specified.
> +
> +  The parameters are defined as seen in the following illustration.
> +
> +  +----------+-------------------------------------+----------+-------+
> +  |          |        ^                            |          |       |
> +  |          |        |vback_porch                 |          |       |
> +  |          |        v                            |          |       |
> +  +----------#######################################----------+-------+
> +  |          #        ^                            #          |       |
> +  |          #        |                            #          |       |
> +  |  hback   #        |                            #  hfront  | hsync |
> +  |   porch  #        |       hactive              #  porch   |  len  |
> +  |<-------->#<-------+--------------------------->#<-------->|<----->|
> +  |          #        |                            #          |       |
> +  |          #        |vactive                     #          |       |
> +  |          #        |                            #          |       |
> +  |          #        v                            #          |       |
> +  +----------#######################################----------+-------+
> +  |          |        ^                            |          |       |
> +  |          |        |vfront_porch                |          |       |
> +  |          |        v                            |          |       |
> +  +----------+-------------------------------------+----------+-------+
> +  |          |        ^                            |          |       |
> +  |          |        |vsync_len                   |          |       |
> +  |          |        v                            |          |       |
> +  +----------+-------------------------------------+----------+-------+
> +
> +
> +  The following is the panel timings shown with time on the x-axis.
> +  This matches the timing diagrams often found in data sheets.
> +
> +              Active                 Front           Sync           Back
> +              Region                 Porch                          Porch
> +  <-----------------------><----------------><-------------><-------------->
> +    //////////////////////|
> +   ////////////////////// |
> +  //////////////////////  |..................               ................
> +                                             _______________
> +
> +  Timing can be specified either as a typical value or as a tuple
> +  of min, typ, max values.
> +
> +properties:
> +
> +  clock-frequency:
> +   $ref: /schemas/types.yaml#/definitions/uint32
> +   description: |
> +     Panel clock in Hz
> +
> +  hactive:
> +    $ref: /schemas/types.yaml#/definitions/uint32
> +    description: |
> +       Horizontal panel resolution in pixels
> +
> +  vactive:
> +    $ref: /schemas/types.yaml#/definitions/uint32
> +    description: |
> +      Verical panel resolution in pixels
> +
> +  hfront-porch:
> +    description: |
> +      Horizontal front porch panel timing
> +    oneOf:
> +      - allOf:
> +        - $ref: /schemas/types.yaml#/definitions/uint32-array
> +        - maxItems: 1
> +          items:
> +            description: typical number of pixels

You have that on a number of occasions, but that could just be an
uint32, right?

> +      - allOf:
> +        - $ref: /schemas/types.yaml#/definitions/uint32-array
> +        - minItems: 3
> +          maxItems: 3
> +          items:
> +            description: min, typ, max number of pixels

When minItems and maxitems are equal, you can just set one, the other
one will be filled by the DT schemas tools.

> +  hsync-active:
> +    description: |
> +      Horizontal sync pulse.
> +      If omitted then it is not used by the hardware
> +    oneOf:
> +      - const: 0
> +        description: active low
> +      - const: 1
> +        description: active high

You probably should use an enum here (and in other similar
places). oneOf / anyOf / allOF errors are pretty cryptic, while it
will it's really better with an enum.

Thanks!
Maxime

Re: [PATCH v1 1/3] dt-bindings: display: add panel-timing.yaml

[Sam Ravnborg]

Hi Maxime.

Thanks for your comments!
> 
> > +      - allOf:
> > +        - $ref: /schemas/types.yaml#/definitions/uint32-array
> > +        - minItems: 3
> > +          maxItems: 3
> > +          items:
> > +            description: min, typ, max number of pixels
> 
> When minItems and maxitems are equal, you can just set one, the other
> one will be filled by the DT schemas tools.

I tried to drop minItems: 3
But it just did not work - I could not make it
accept <xx> and <xx xx xx>.

And the schema should, and does, reject <xx xx> and <xx xx xx xx>

I do not know why - I just did a trial-and-error on this.

> > +  hsync-active:
> > +    description: |
> > +      Horizontal sync pulse.
> > +      If omitted then it is not used by the hardware
> > +    oneOf:
> > +      - const: 0
> > +        description: active low
> > +      - const: 1
> > +        description: active high
> 
> You probably should use an enum here (and in other similar
> places). oneOf / anyOf / allOF errors are pretty cryptic, while it
> will it's really better with an enum.

Yep - enum: [0, 1] is much nicer.

	Sam

Re: [PATCH v1 1/3] dt-bindings: display: add panel-timing.yaml

[Rob Herring]

On Mon, Jan 20, 2020 at 2:07 PM Sam Ravnborg <sam@ravnborg.org> wrote:
>
> Add meta-schema variant of panel-timing and
> reference it from panel-common.yaml.
>
> Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
> Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> Cc: Rob Herring <robh@kernel.org>
> Cc: Thierry Reding <thierry.reding@gmail.com>
> Cc: Oleksandr Suvorov <oleksandr.suvorov@toradex.com>
> Cc: devicetree@vger.kernel.org
> ---
>  .../bindings/display/panel/panel-common.yaml  |   7 +-
>  .../bindings/display/panel/panel-timing.yaml  | 253 ++++++++++++++++++
>  2 files changed, 256 insertions(+), 4 deletions(-)
>  create mode 100644 Documentation/devicetree/bindings/display/panel/panel-timing.yaml
>
> diff --git a/Documentation/devicetree/bindings/display/panel/panel-common.yaml b/Documentation/devicetree/bindings/display/panel/panel-common.yaml
> index ef8d8cdfcede..8070c439adbd 100644
> --- a/Documentation/devicetree/bindings/display/panel/panel-common.yaml
> +++ b/Documentation/devicetree/bindings/display/panel/panel-common.yaml
> @@ -54,13 +54,12 @@ properties:
>
>    # Display Timings
>    panel-timing:
> -    type: object
>      description:
>        Most display panels are restricted to a single resolution and
>        require specific display timings. The panel-timing subnode expresses those
> -      timings as specified in the timing subnode section of the display timing
> -      bindings defined in
> -      Documentation/devicetree/bindings/display/panel/display-timing.txt.
> +      timings.
> +    allOf:
> +      - $ref: panel-timing.yaml#
>
>    # Connectivity
>    port:
> diff --git a/Documentation/devicetree/bindings/display/panel/panel-timing.yaml b/Documentation/devicetree/bindings/display/panel/panel-timing.yaml
> new file mode 100644
> index 000000000000..59891c7a58ee
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/display/panel/panel-timing.yaml
> @@ -0,0 +1,253 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)

Some of this comes from the existing binding files, do you have rights
to change the license (it would be nice to get it).

> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/display/panel/panel-timing.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: panel timing bindings
> +
> +maintainers:
> +  - Thierry Reding <thierry.reding@gmail.com>
> +  - Sam Ravnborg <sam@ravnborg.org>
> +
> +description: |
> +  There are different ways of describing the timing data data of a panel. The
> +  devicetree representation corresponds to the one commonly found in datasheets
> +  for panels. If a panel supports multiple signal timings, the native-mode
> +  can be specified.
> +
> +  The parameters are defined as seen in the following illustration.
> +
> +  +----------+-------------------------------------+----------+-------+
> +  |          |        ^                            |          |       |
> +  |          |        |vback_porch                 |          |       |
> +  |          |        v                            |          |       |
> +  +----------#######################################----------+-------+
> +  |          #        ^                            #          |       |
> +  |          #        |                            #          |       |
> +  |  hback   #        |                            #  hfront  | hsync |
> +  |   porch  #        |       hactive              #  porch   |  len  |
> +  |<-------->#<-------+--------------------------->#<-------->|<----->|
> +  |          #        |                            #          |       |
> +  |          #        |vactive                     #          |       |
> +  |          #        |                            #          |       |
> +  |          #        v                            #          |       |
> +  +----------#######################################----------+-------+
> +  |          |        ^                            |          |       |
> +  |          |        |vfront_porch                |          |       |
> +  |          |        v                            |          |       |
> +  +----------+-------------------------------------+----------+-------+
> +  |          |        ^                            |          |       |
> +  |          |        |vsync_len                   |          |       |
> +  |          |        v                            |          |       |
> +  +----------+-------------------------------------+----------+-------+
> +
> +
> +  The following is the panel timings shown with time on the x-axis.
> +  This matches the timing diagrams often found in data sheets.
> +
> +              Active                 Front           Sync           Back
> +              Region                 Porch                          Porch
> +  <-----------------------><----------------><-------------><-------------->
> +    //////////////////////|
> +   ////////////////////// |
> +  //////////////////////  |..................               ................
> +                                             _______________
> +
> +  Timing can be specified either as a typical value or as a tuple
> +  of min, typ, max values.
> +
> +properties:
> +
> +  clock-frequency:
> +   $ref: /schemas/types.yaml#/definitions/uint32

There's already a type definition for this.

> +   description: |

Drop '|' unless you have multiple paragraphs or need to maintain formatting.

> +     Panel clock in Hz
> +
> +  hactive:
> +    $ref: /schemas/types.yaml#/definitions/uint32
> +    description: |
> +       Horizontal panel resolution in pixels
> +
> +  vactive:
> +    $ref: /schemas/types.yaml#/definitions/uint32
> +    description: |
> +      Verical panel resolution in pixels

typo

> +
> +  hfront-porch:
> +    description: |
> +      Horizontal front porch panel timing
> +    oneOf:
> +      - allOf:
> +        - $ref: /schemas/types.yaml#/definitions/uint32-array
> +        - maxItems: 1
> +          items:
> +            description: typical number of pixels
> +      - allOf:
> +        - $ref: /schemas/types.yaml#/definitions/uint32-array
> +        - minItems: 3
> +          maxItems: 3
> +          items:
> +            description: min, typ, max number of pixels

I think you can describe it like this (test with 2 items though):

allOf:
  - $ref: /schemas/types.yaml#/definitions/uint32-array
not:
  maxItems: 2
items:
  - description: ...
  - description: ...
  - description: ...

> +
> +  hback-porch:
> +    description: |
> +      Horizontal back porch timing
> +    oneOf:
> +      - allOf:
> +        - $ref: /schemas/types.yaml#/definitions/uint32-array
> +        - maxItems: 1
> +          items:
> +            description: typical number of pixels
> +      - allOf:
> +        - $ref: /schemas/types.yaml#/definitions/uint32-array
> +        - minItems: 3
> +          maxItems: 3
> +          items:
> +            description: min, typ, max number of pixels
> +
> +  hsync-len:
> +    description: |
> +      Horizontal sync length panel timing
> +    oneOf:
> +      - allOf:
> +        - $ref: /schemas/types.yaml#/definitions/uint32-array
> +        - maxItems: 1
> +          items:
> +            description: typical number of pixels
> +      - allOf:
> +        - $ref: /schemas/types.yaml#/definitions/uint32-array
> +        - minItems: 3
> +          maxItems: 3
> +          items:
> +            description: min, typ, max number of pixels
> +
> +  vfront-porch:
> +    description: |
> +      Vertical front porch panel timing
> +    oneOf:
> +      - allOf:
> +        - $ref: /schemas/types.yaml#/definitions/uint32-array
> +        - maxItems: 1
> +          items:
> +            description: typical number of lines
> +      - allOf:
> +        - $ref: /schemas/types.yaml#/definitions/uint32-array
> +        - minItems: 3
> +          maxItems: 3
> +          items:
> +            description: min, typ, max number of lines
> +
> +  vback-porch:
> +    description: |
> +      Vertical back porch panel timing
> +    oneOf:
> +      - allOf:
> +        - $ref: /schemas/types.yaml#/definitions/uint32-array
> +        - maxItems: 1
> +          items:
> +            description: typical number of lines
> +      - allOf:
> +        - $ref: /schemas/types.yaml#/definitions/uint32-array
> +        - minItems: 3
> +          maxItems: 3
> +          items:
> +            description: min, typ, max number of lines
> +
> +  vsync-len:
> +    description: |
> +      Vertical sync length panel timing
> +    oneOf:
> +      - allOf:
> +        - $ref: /schemas/types.yaml#/definitions/uint32-array
> +        - maxItems: 1
> +          items:
> +            description: typical number of lines
> +      - allOf:
> +        - $ref: /schemas/types.yaml#/definitions/uint32-array
> +        - minItems: 3
> +          maxItems: 3
> +          items:
> +            description: min, typ, max number of lines
> +
> +  hsync-active:
> +    description: |
> +      Horizontal sync pulse.
> +      If omitted then it is not used by the hardware
> +    oneOf:
> +      - const: 0
> +        description: active low
> +      - const: 1
> +        description: active high
> +
> +  vsync-active:
> +    description: |
> +      Vertical sync pulse.
> +      If omitted then it is not used by the hardware
> +    oneOf:
> +      - const: 0
> +        description: active low
> +      - const: 1
> +        description: active high
> +
> +  de-active:
> +    description: |
> +      Data enable.
> +      If omitted then it is not used by the hardware
> +    oneOf:
> +      - const: 0
> +        description: active low
> +      - const: 1
> +        description: active high
> +
> +  pixelclk-active:
> +    description: |
> +      Data driving on rising or falling edge
> +    oneOf:
> +      - const: 0
> +        description: |
> +          Drive pixel data on falling edge and
> +          sample data on rising edge
> +      - const: 1
> +        description: |
> +          Drive pixel data on rising edge and
> +          sample data on falling edge
> +
> +  syncclk-active:
> +    description: |
> +      Drive sync on rising or sample sync on falling edge.
> +      If not specified then the same as pixelclk-active
> +    oneOf:
> +      - const: 0
> +        description: |
> +          Drive sync on falling edge and
> +          sample sync on rising edge of pixel clock
> +      - const: 1
> +        description: |
> +          Drive sync on rising edge and
> +          sample sync on falling edge of pixel clock
> +
> +  interlaced:
> +    type: boolean
> +    description: Enable interlaced mode
> +
> +  doublescan:
> +    type: boolean
> +    description: Enable double scan mode
> +
> +  doubleclk:
> +    type: boolean
> +    description: Enable double clock mode
> +
> +required:
> + - clock-frequency
> + - hactive
> + - vactive
> + - hfront-porch
> + - hback-porch
> + - hsync-len
> + - vfront-porch
> + - vback-porch
> + - vsync-len
> +
> +additionalProperties: false
> --
> 2.20.1
>

[PATCH v1 2/3] dt-bindings: display: convert display-timings to DT schema

[Sam Ravnborg]

Add display-timings.yaml - that references panel-timings.yaml.
display-timings.yaml will be used for display bindings
when they are converted to meta-schema format.

For now the old display-timing.txt points to the new
display-timings.yaml - and all users are left as-is.

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Cc: Rob Herring <robh@kernel.org>
Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: Thierry Reding <thierry.reding@gmail.com>
Cc: Oleksandr Suvorov <oleksandr.suvorov@toradex.com>
Cc: devicetree@vger.kernel.org
---
 .../bindings/display/panel/display-timing.txt | 124 +-----------------
 .../display/panel/display-timings.yaml        |  67 ++++++++++
 2 files changed, 68 insertions(+), 123 deletions(-)
 create mode 100644 Documentation/devicetree/bindings/display/panel/display-timings.yaml

diff --git a/Documentation/devicetree/bindings/display/panel/display-timing.txt b/Documentation/devicetree/bindings/display/panel/display-timing.txt
index 78222ced1874..7f55ad4a40c4 100644
--- a/Documentation/devicetree/bindings/display/panel/display-timing.txt
+++ b/Documentation/devicetree/bindings/display/panel/display-timing.txt
@@ -1,123 +1 @@
-display-timing bindings
-=======================
-
-display-timings node
---------------------
-
-required properties:
- - none
-
-optional properties:
- - native-mode: The native mode for the display, in case multiple modes are
-		provided. When omitted, assume the first node is the native.
-
-timing subnode
---------------
-
-required properties:
- - hactive, vactive: display resolution
- - hfront-porch, hback-porch, hsync-len: horizontal display timing parameters
-   in pixels
-   vfront-porch, vback-porch, vsync-len: vertical display timing parameters in
-   lines
- - clock-frequency: display clock in Hz
-
-optional properties:
- - hsync-active: hsync pulse is active low/high/ignored
- - vsync-active: vsync pulse is active low/high/ignored
- - de-active: data-enable pulse is active low/high/ignored
- - pixelclk-active: with
-			- active high = drive pixel data on rising edge/
-					sample data on falling edge
-			- active low  = drive pixel data on falling edge/
-					sample data on rising edge
-			- ignored     = ignored
- - syncclk-active: with
-			- active high = drive sync on rising edge/
-					sample sync on falling edge of pixel
-					clock
-			- active low  = drive sync on falling edge/
-					sample sync on rising edge of pixel
-					clock
-			- omitted     = same configuration as pixelclk-active
- - interlaced (bool): boolean to enable interlaced mode
- - doublescan (bool): boolean to enable doublescan mode
- - doubleclk (bool): boolean to enable doubleclock mode
-
-All the optional properties that are not bool follow the following logic:
-    <1>: high active
-    <0>: low active
-    omitted: not used on hardware
-
-There are different ways of describing the capabilities of a display. The
-devicetree representation corresponds to the one commonly found in datasheets
-for displays. If a display supports multiple signal timings, the native-mode
-can be specified.
-
-The parameters are defined as:
-
-  +----------+-------------------------------------+----------+-------+
-  |          |        ^                            |          |       |
-  |          |        |vback_porch                 |          |       |
-  |          |        v                            |          |       |
-  +----------#######################################----------+-------+
-  |          #        ^                            #          |       |
-  |          #        |                            #          |       |
-  |  hback   #        |                            #  hfront  | hsync |
-  |   porch  #        |       hactive              #  porch   |  len  |
-  |<-------->#<-------+--------------------------->#<-------->|<----->|
-  |          #        |                            #          |       |
-  |          #        |vactive                     #          |       |
-  |          #        |                            #          |       |
-  |          #        v                            #          |       |
-  +----------#######################################----------+-------+
-  |          |        ^                            |          |       |
-  |          |        |vfront_porch                |          |       |
-  |          |        v                            |          |       |
-  +----------+-------------------------------------+----------+-------+
-  |          |        ^                            |          |       |
-  |          |        |vsync_len                   |          |       |
-  |          |        v                            |          |       |
-  +----------+-------------------------------------+----------+-------+
-
-Note: In addition to being used as subnode(s) of display-timings, the timing
-      subnode may also be used on its own. This is appropriate if only one mode
-      need be conveyed. In this case, the node should be named 'panel-timing'.
-
-
-Example:
-
-	display-timings {
-		native-mode = <&timing0>;
-		timing0: 1080p24 {
-			/* 1920x1080p24 */
-			clock-frequency = <52000000>;
-			hactive = <1920>;
-			vactive = <1080>;
-			hfront-porch = <25>;
-			hback-porch = <25>;
-			hsync-len = <25>;
-			vback-porch = <2>;
-			vfront-porch = <2>;
-			vsync-len = <2>;
-			hsync-active = <1>;
-		};
-	};
-
-Every required property also supports the use of ranges, so the commonly used
-datasheet description with minimum, typical and maximum values can be used.
-
-Example:
-
-	timing1: timing {
-		/* 1920x1080p24 */
-		clock-frequency = <148500000>;
-		hactive = <1920>;
-		vactive = <1080>;
-		hsync-len = <0 44 60>;
-		hfront-porch = <80 88 95>;
-		hback-porch = <100 148 160>;
-		vfront-porch = <0 4 6>;
-		vback-porch = <0 36 50>;
-		vsync-len = <0 5 6>;
-	};
+See display-timings.yaml in this directory.
diff --git a/Documentation/devicetree/bindings/display/panel/display-timings.yaml b/Documentation/devicetree/bindings/display/panel/display-timings.yaml
new file mode 100644
index 000000000000..4f93a4a287d3
--- /dev/null
+++ b/Documentation/devicetree/bindings/display/panel/display-timings.yaml
@@ -0,0 +1,67 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/display/panel/display-timings.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: display timing bindings
+
+maintainers:
+  - Thierry Reding <thierry.reding@gmail.com>
+  - Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
+  - Sam Ravnborg <sam@ravnborg.org>
+
+properties:
+  $nodename:
+    const: display-timings
+
+  native-mode:
+    $ref: /schemas/types.yaml#/definitions/phandle
+    description: |
+      The native mode for the display, in case multiple modes are
+      provided. When omitted, assume the first node is the native.
+
+patternProperties:
+  "^timing.*$":
+    allOf:
+      - $ref: panel-timing.yaml#
+
+additionalProperties: false
+
+examples:
+  - |+
+
+    /*
+     * Example that specifies panel timing using minimum, typical,
+     * maximum values as commonly used in datasheet description.
+     * timing1 is the native-mode.
+     */
+    display-timings {
+      native-mode = <&timing1>;
+      timing0 {
+        /* 1920x1080p24 */
+        clock-frequency = <148500000>;
+        hactive = <1920>;
+        vactive = <1080>;
+        hsync-len = <0 44 60>;
+        hfront-porch = <80 88 95>;
+        hback-porch = <100 148 160>;
+        vfront-porch = <0 4 6>;
+        vback-porch = <0 36 50>;
+        vsync-len = <0 5 6>;
+      };
+      timing1 {
+        /* 1920x1080p24 */
+        clock-frequency = <52000000>;
+        hactive = <1920>;
+        vactive = <1080>;
+        hfront-porch = <25>;
+        hback-porch = <25>;
+        hsync-len = <0 25 25>;
+        vback-porch = <2>;
+        vfront-porch = <2>;
+        vsync-len = <2>;
+        hsync-active = <1>;
+        pixelclk-active = <1>;
+      };
+    };
-- 
2.20.1

[PATCH v1 3/3] dt-bindings: display: convert panel-dpi to DT schema

[Sam Ravnborg]

With panel-timing converted, now convert the single
remaining .txt user in panel/ of panel-timing to DT schema.

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Cc: Rob Herring <robh@kernel.org>
Cc: Thierry Reding <thierry.reding@gmail.com>
Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: Maxime Ripard <mripard@kernel.org>
---
 .../bindings/display/panel/panel-dpi.txt      | 50 -------------
 .../bindings/display/panel/panel-dpi.yaml     | 71 +++++++++++++++++++
 2 files changed, 71 insertions(+), 50 deletions(-)
 delete mode 100644 Documentation/devicetree/bindings/display/panel/panel-dpi.txt
 create mode 100644 Documentation/devicetree/bindings/display/panel/panel-dpi.yaml

diff --git a/Documentation/devicetree/bindings/display/panel/panel-dpi.txt b/Documentation/devicetree/bindings/display/panel/panel-dpi.txt
deleted file mode 100644
index 6b203bc4d932..000000000000
--- a/Documentation/devicetree/bindings/display/panel/panel-dpi.txt
+++ /dev/null
@@ -1,50 +0,0 @@
-Generic MIPI DPI Panel
-======================
-
-Required properties:
-- compatible: "panel-dpi"
-
-Optional properties:
-- label: a symbolic name for the panel
-- enable-gpios: panel enable gpio
-- reset-gpios: GPIO to control the RESET pin
-- vcc-supply: phandle of regulator that will be used to enable power to the display
-- backlight: phandle of the backlight device
-
-Required nodes:
-- "panel-timing" containing video timings
-  (Documentation/devicetree/bindings/display/panel/display-timing.txt)
-- Video port for DPI input
-
-Example
--------
-
-lcd0: display@0 {
-        compatible = "samsung,lte430wq-f0c", "panel-dpi";
-        label = "lcd";
-
-        backlight = <&backlight>;
-
-        port {
-            lcd_in: endpoint {
-                    remote-endpoint = <&dpi_out>;
-            };
-        };
-
-        panel-timing {
-                clock-frequency = <9200000>;
-                hactive = <480>;
-                vactive = <272>;
-                hfront-porch = <8>;
-                hback-porch = <4>;
-                hsync-len = <41>;
-                vback-porch = <2>;
-                vfront-porch = <4>;
-                vsync-len = <10>;
-
-                hsync-active = <0>;
-                vsync-active = <0>;
-                de-active = <1>;
-                pixelclk-active = <1>;
-        };
-};
diff --git a/Documentation/devicetree/bindings/display/panel/panel-dpi.yaml b/Documentation/devicetree/bindings/display/panel/panel-dpi.yaml
new file mode 100644
index 000000000000..4e19c1fd52c3
--- /dev/null
+++ b/Documentation/devicetree/bindings/display/panel/panel-dpi.yaml
@@ -0,0 +1,71 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/display/panel/panel-dpi.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Generic MIPI DPI Panel
+
+maintainers:
+  - Sam Ravnborg <sam@ravnborg.org>
+  - Thierry Reding <thierry.reding@gmail.com>
+
+allOf:
+  - $ref: panel-common.yaml#
+
+properties:
+  compatible:
+    contains:
+      const: panel-dpi
+    description:
+      Shall contain "panel-dpi" in addition to a mandatory panel-specific
+      compatible string defined in individual panel bindings. The "panel-dpi"
+      value shall never be used on its own.
+
+  vcc-supply:
+    description: |
+      Regulator that will be used to enable power to the display
+
+  label: true
+  enable-gpios: true
+  reset-gpios: true
+  backlight: true
+  panel-timing: true
+  port: true
+
+required:
+  - panel-timing
+
+additionalProperties: false
+
+examples:
+  - |
+    panel@0 {
+      compatible = "samsung,lte430wq-f0c", "panel-dpi";
+      label = "lcd";
+      vcc-supply = <&vcc_supply>;
+
+      backlight = <&backlight>;
+
+      port {
+        lcd_in: endpoint {
+          remote-endpoint = <&dpi_out>;
+        };
+      };
+      panel-timing {
+        clock-frequency = <9200000>;
+        hactive = <480>;
+        vactive = <272>;
+        hfront-porch = <8>;
+        hback-porch = <4>;
+        hsync-len = <41>;
+        vback-porch = <2>;
+        vfront-porch = <4>;
+        vsync-len = <10>;
+
+        hsync-active = <0>;
+        vsync-active = <0>;
+        de-active = <1>;
+        pixelclk-active = <1>;
+      };
+    };
-- 
2.20.1

Re: [PATCH v1 3/3] dt-bindings: display: convert panel-dpi to DT schema

[Rob Herring]

On Mon, Jan 20, 2020 at 2:07 PM Sam Ravnborg <sam@ravnborg.org> wrote:
>
> With panel-timing converted, now convert the single
> remaining .txt user in panel/ of panel-timing to DT schema.
>
> Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
> Cc: Rob Herring <robh@kernel.org>
> Cc: Thierry Reding <thierry.reding@gmail.com>
> Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> Cc: Maxime Ripard <mripard@kernel.org>
> ---
>  .../bindings/display/panel/panel-dpi.txt      | 50 -------------
>  .../bindings/display/panel/panel-dpi.yaml     | 71 +++++++++++++++++++
>  2 files changed, 71 insertions(+), 50 deletions(-)
>  delete mode 100644 Documentation/devicetree/bindings/display/panel/panel-dpi.txt
>  create mode 100644 Documentation/devicetree/bindings/display/panel/panel-dpi.yaml

[...]

> diff --git a/Documentation/devicetree/bindings/display/panel/panel-dpi.yaml b/Documentation/devicetree/bindings/display/panel/panel-dpi.yaml
> new file mode 100644
> index 000000000000..4e19c1fd52c3
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/display/panel/panel-dpi.yaml
> @@ -0,0 +1,71 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/display/panel/panel-dpi.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Generic MIPI DPI Panel
> +
> +maintainers:
> +  - Sam Ravnborg <sam@ravnborg.org>
> +  - Thierry Reding <thierry.reding@gmail.com>
> +
> +allOf:
> +  - $ref: panel-common.yaml#
> +
> +properties:
> +  compatible:
> +    contains:
> +      const: panel-dpi
> +    description:
> +      Shall contain "panel-dpi" in addition to a mandatory panel-specific
> +      compatible string defined in individual panel bindings. The "panel-dpi"
> +      value shall never be used on its own.

Yet we have 3 cases where it is...

A 'minItems: 2' should be enough to catch these. Or do:

items:
  - {}
  - const: panel-dpi

Or list the panel compatible that's in the example. That way we'll get
errors for all the undocumented panel compatibles (that's most of
them).

> +
> +  vcc-supply:
> +    description: |
> +      Regulator that will be used to enable power to the display
> +
> +  label: true
> +  enable-gpios: true
> +  reset-gpios: true
> +  backlight: true
> +  panel-timing: true
> +  port: true
> +
> +required:
> +  - panel-timing
> +
> +additionalProperties: false
> +
> +examples:
> +  - |
> +    panel@0 {
> +      compatible = "samsung,lte430wq-f0c", "panel-dpi";
> +      label = "lcd";
> +      vcc-supply = <&vcc_supply>;
> +
> +      backlight = <&backlight>;
> +
> +      port {
> +        lcd_in: endpoint {
> +          remote-endpoint = <&dpi_out>;
> +        };
> +      };
> +      panel-timing {
> +        clock-frequency = <9200000>;
> +        hactive = <480>;
> +        vactive = <272>;
> +        hfront-porch = <8>;
> +        hback-porch = <4>;
> +        hsync-len = <41>;
> +        vback-porch = <2>;
> +        vfront-porch = <4>;
> +        vsync-len = <10>;
> +
> +        hsync-active = <0>;
> +        vsync-active = <0>;
> +        de-active = <1>;
> +        pixelclk-active = <1>;
> +      };
> +    };
> --
> 2.20.1
>

Re: [PATCH v1 3/3] dt-bindings: display: convert panel-dpi to DT schema

[Sam Ravnborg]

Hi Rob.

On Tue, Jan 21, 2020 at 08:50:25AM -0600, Rob Herring wrote:
> On Mon, Jan 20, 2020 at 2:07 PM Sam Ravnborg <sam@ravnborg.org> wrote:
> >
> > With panel-timing converted, now convert the single
> > remaining .txt user in panel/ of panel-timing to DT schema.
> >
> > Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
> > Cc: Rob Herring <robh@kernel.org>
> > Cc: Thierry Reding <thierry.reding@gmail.com>
> > Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> > Cc: Maxime Ripard <mripard@kernel.org>
> > ---
> >  .../bindings/display/panel/panel-dpi.txt      | 50 -------------
> >  .../bindings/display/panel/panel-dpi.yaml     | 71 +++++++++++++++++++
> >  2 files changed, 71 insertions(+), 50 deletions(-)
> >  delete mode 100644 Documentation/devicetree/bindings/display/panel/panel-dpi.txt
> >  create mode 100644 Documentation/devicetree/bindings/display/panel/panel-dpi.yaml
> 
> [...]
> 
> > diff --git a/Documentation/devicetree/bindings/display/panel/panel-dpi.yaml b/Documentation/devicetree/bindings/display/panel/panel-dpi.yaml
> > new file mode 100644
> > index 000000000000..4e19c1fd52c3
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/display/panel/panel-dpi.yaml
> > @@ -0,0 +1,71 @@
> > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> > +%YAML 1.2
> > +---
> > +$id: http://devicetree.org/schemas/display/panel/panel-dpi.yaml#
> > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > +
> > +title: Generic MIPI DPI Panel
> > +
> > +maintainers:
> > +  - Sam Ravnborg <sam@ravnborg.org>
> > +  - Thierry Reding <thierry.reding@gmail.com>
> > +
> > +allOf:
> > +  - $ref: panel-common.yaml#
> > +
> > +properties:
> > +  compatible:
> > +    contains:
> > +      const: panel-dpi
> > +    description:
> > +      Shall contain "panel-dpi" in addition to a mandatory panel-specific
> > +      compatible string defined in individual panel bindings. The "panel-dpi"
> > +      value shall never be used on its own.
> 
> Yet we have 3 cases where it is...
> 
> A 'minItems: 2' should be enough to catch these. Or do:

The above was a verbatim copy from another binding.
Thinking more about this I went with this:

  compatible:
    contains:
      const: panel-dpi
    description:
      Shall contain "panel-dpi" in addition to an optional panel-specific
      compatible string defined in individual panel bindings.
      "panel-dpi" can be used alone, thus no dedicated binding file
      is required for each and every panel.

So a DT file with:
panel@0 {
      compatible = "panel-dpi";
      ...
      panel-timing {
        ...
      };

Is in many cases enough - and then people do not have
to either cheat or wait until their panel is included in the kernel.
The panel market i big, and there are new panels each and every day.
With panel-dpi we can support the dumb panels that
do not require any special delays etc.

	Sam