Re: [PATCH 3/6] dt-bindings: connector: Add Toradex camera connector

[Ernest Van Hoecke]

Hi Frank,

Thanks for reviewing this so quickly.

On Thu, Sep 10, 2026 at 11:26:22AM -0500, Frank Li wrote:
> On Thu, Sep 10, 2026 at 05:37:59PM +0200, Ernest Van Hoecke wrote:
> > From: Ernest Van Hoecke <ernest.vanhoecke@xxxxxxxxxxx>
> >
> > Toradex boards route the sideband signals of their 24-pin camera
> > connectors to different GPIO controllers. Camera overlays which name
> > those controllers directly must therefore be duplicated for each host
> > board.
> >
> > Describe reset, power-down, detection and power-control as
> > connector-local GPIO functions. This lets an accessory overlay remain
> > independent of the host wiring. MIPI CSI-2, I2C, clocks and supplies
> > remain described separately because the GPIO nexus does not abstract
> > them.
> >
> > Signed-off-by: Ernest Van Hoecke <ernest.vanhoecke@xxxxxxxxxxx>
> > ---
> >  .../connector/toradex,camera-connector.yaml        | 86 ++++++++++++++++++++++
> >  1 file changed, 86 insertions(+)
> >
> > diff --git a/Documentation/devicetree/bindings/connector/toradex,camera-connector.yaml b/Documentation/devicetree/bindings/connector/toradex,camera-connector.yaml
> > new file mode 100644
> > index 000000000000..06e6836e1aa6
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/connector/toradex,camera-connector.yaml
> > @@ -0,0 +1,86 @@
> > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> > +%YAML 1.2
> > +---
> > +$id: http://devicetree.org/schemas/connector/toradex,camera-connector.yaml#
> > +$schema: http://devicetree.org/meta-schemas/base.yaml#
> > +
> > +title: Toradex camera connector GPIO nexus
> > +
> > +maintainers:
> > +  - Ernest Van Hoecke <ernest.vanhoecke@xxxxxxxxxxx>
> > +  - Toradex Linux BSP Team <linux-bsp@xxxxxxxxxxx>
> > +
> > +description: |
> > +  Toradex boards provide 24-pin camera connectors carrying MIPI CSI-2, I2C,
> > +  clock, power, and sideband GPIO signals. This binding describes the sideband
> > +  signals as a GPIO nexus. The other connector resources remain described by
> > +  the surrounding board device tree.
> > +
> > +  The nexus exposes connector-local GPIO function numbers to camera overlays
> > +  and maps the functions wired by a carrier board to their GPIO controllers.
> > +  GPIO specifiers contain a function number followed by standard GPIO flags.
> > +  A board may omit functions which it does not wire.
> > +
> > +  The function numbers are:
> > +    - 0: Camera reset, connector pin 11
> > +    - 1: Camera power-down, connector pin 22
> > +    - 2: Camera identification, connector pin 23
> > +    - 3: Camera power control, connector pin 24
> > +
> > +properties:
> > +  compatible:
> > +    const: toradex,camera-connector
> 
> Name is too generally, suggest use board name, we got similar comments at
> 
> https://lore.kernel.org/imx/20260629074734.3643227-2-chancel.liu@xxxxxxxxxxx/

I saw that and it made me reconsider this name.

However, I believe that in our case it is specific enough. It is really
the same on all our carrier boards, and Toradex specific. It's also only
for cameras, which is more defined than just "io". Curious to see if
others agree or if we should come up with a name for this.
 
> > +
> > +  "#gpio-cells":
> > +    const: 2
> > +
> > +  gpio-map:
> > +    minItems: 1
> > +    maxItems: 4
> > +
> > +  gpio-map-mask:
> > +    items:
> > +      - const: 0xffffffff
> 
> are you sure need full 32bit, only 4 pin, maybe 0xf should enough?
> 

Indeed we could reduce the size of the mask, but I don't really see the
value in it. Isn't it good that a user can pass through the full GPIO?

> > +      - const: 0
> > +
> > +  gpio-map-pass-thru:
> > +    items:
> > +      - const: 0
> > +      - const: 0xffffffff
> > +
> 
> missed
> 	gpio-controller: true
> 

This is one thing I didn't fully understand about the GPIO nexus
concept, why would we need this gpio-controller flag? Isn't the gpio
controller behind the nexus? The nexus just maps onto it. The actual
controller would be on the SoC or an expander.

> > +required:
> > +  - compatible
> > +  - "#gpio-cells"
> > +  - gpio-map
> > +  - gpio-map-mask
> > +  - gpio-map-pass-thru
> > +
> > +additionalProperties: false
> > +
> > +examples:
> > +  - |
> > +    #include <dt-bindings/gpio/gpio.h>
> > +
> > +    camera-connector {
> > +        compatible = "toradex,camera-connector";
> > +        #gpio-cells = <2>;
> > +        /*
> > +         * 0: Camera reset, connector pin 11
> > +         * 1: Camera power-down, connector pin 22
> > +         * 2: Camera identification, connector pin 23
> > +         * 3: Camera power control, connector pin 24
> > +         */
> > +        gpio-map = <0 0 &gpio1 0 GPIO_ACTIVE_HIGH>,
> > +                   <1 0 &gpio1 1 GPIO_ACTIVE_HIGH>,
> > +                   <2 0 &gpio1 2 GPIO_ACTIVE_HIGH>,
> > +                   <3 0 &gpio1 3 GPIO_ACTIVE_HIGH>;
> > +        gpio-map-mask = <0xffffffff 0x0>;
> > +        gpio-map-pass-thru = <0x0 0xffffffff>;
> > +    };
> > +
> > +    gpio1: gpio-controller {
> > +        #gpio-cells = <2>;
> > +        gpio-controller;
> > +    };
> 
> Need't gpio-controller.
> 
> Frank
> 

This ties in to my same confusion above, could you explain why or point
me to a relevant example/docs?

Thanks and kind regards,
Ernest