dt-bindings: usb: usb-device: Add panel-location

For some devices like cameras the system needs to know where they are
mounted.

ACPI has a property for this purpose, which is parsed by
acpi_get_physical_device_location():
https://uefi.org/htmlspecs/ACPI_Spec_6_4_html/06_Device_Configuration/Device_Configuration.html#pld-physical-location-of-device

In DT we have similar property for video-interface-devices called
orientation, but it is limited to the requirements of video devices:
Documentation/devicetree/bindings/media/video-interface-devices.yaml

Add a new property for usb-devices that matches the behavior of
ACPI's _PLD.

Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
---
 Documentation/devicetree/bindings/usb/usb-device.yaml | 14 ++++++++++++++
 1 file changed, 14 insertions(+)


---
base-commit: eefa7a9c069908412f8f5d15833901d1b46ae1b2
change-id: 20241212-usb-orientation-8e3717ebb02a

Best regards,

On Thu, Dec 12, 2024 at 09:44:37PM +0000, Ricardo Ribalda wrote:
> For some devices like cameras the system needs to know where they are
> mounted.

Why do you need this and why only this property and not the dozens 
others ACPI has?

> 
> ACPI has a property for this purpose, which is parsed by
> acpi_get_physical_device_location():
> https://uefi.org/htmlspecs/ACPI_Spec_6_4_html/06_Device_Configuration/Device_Configuration.html#pld-physical-location-of-device
> 
> In DT we have similar property for video-interface-devices called
> orientation, but it is limited to the requirements of video devices:
> Documentation/devicetree/bindings/media/video-interface-devices.yaml
> 
> Add a new property for usb-devices that matches the behavior of
> ACPI's _PLD.
> 
> Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
> ---
>  Documentation/devicetree/bindings/usb/usb-device.yaml | 14 ++++++++++++++
>  1 file changed, 14 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/usb/usb-device.yaml b/Documentation/devicetree/bindings/usb/usb-device.yaml
> index da890ee60ce6..1ce79c1c3b31 100644
> --- a/Documentation/devicetree/bindings/usb/usb-device.yaml
> +++ b/Documentation/devicetree/bindings/usb/usb-device.yaml
> @@ -42,6 +42,20 @@ properties:
>        port to which this device is attached. The range is 1-255.
>      maxItems: 1
>  
> +  panel-location:
> +    description: Describes which panel surface of the system's housing the USB
> +      device resides on. It has the same meaning as the `ACPI`'s `_PLD` Panel
> +      object.
> +    $ref: /schemas/types.yaml#/definitions/uint32
> +    enum:
> +      - 0 # Top.
> +      - 1 # Bottom.
> +      - 2 # Left.
> +      - 3 # Right.
> +      - 4 # Front (aka as User Facing).
> +      - 5 # Back (aka as World Facing).
> +      - 6 # Unknown.
> +
>    "#address-cells":
>      description: should be 1 for hub nodes with device nodes,
>        should be 2 for device nodes with interface nodes.
> 
> ---
> base-commit: eefa7a9c069908412f8f5d15833901d1b46ae1b2
> change-id: 20241212-usb-orientation-8e3717ebb02a
> 
> Best regards,
> -- 
> Ricardo Ribalda <ribalda@chromium.org>
>

On Thu, 19 Dec 2024 at 13:24, Rob Herring <robh@kernel.org> wrote:
>
> On Tue, Dec 17, 2024 at 04:24:27PM +0100, Ricardo Ribalda wrote:
> > Hi Rob
> >
> > On Tue, 17 Dec 2024 at 16:02, Rob Herring <robh@kernel.org> wrote:
> > >
> > > On Thu, Dec 12, 2024 at 09:44:37PM +0000, Ricardo Ribalda wrote:
> > > > For some devices like cameras the system needs to know where they are
> > > > mounted.
> > >
> > > Why do you need this and why only this property and not the dozens
> > > others ACPI has?
> >
> > Userspace needs that information to correctly show it in the UI. Eg;
> >
> > - User facing camera needs to be mirrored during preview.
> > - The user facing camera is selected by default during videoconferences
> > - The world facing camera is selected by default when taking a photo
> > - User facing camera have different parameter defaults than world facing.
>
> We already have "orientation" defined for this purpose.

Do you mean orientation from
bindings/media/video-interface-devices.yaml ?

I see a couple of issues:
- Orientation has a very specific meaning for USB typeC. I'd prefer if
we could avoid using that word.
- For other applications different than cameras it might be useful to
know the positions top, bottom, left, right, which are not available
in video-interface-devices
- The value "external" does not makes too much sense for listed usb devices
- It makes our lives easier if dt and acpi have the same meaning (less
conversion)

All that said, for my specific usecase, reusing orientation from
bindings/media/video-interface-devices.yaml works... So if that is
what you all prefer I can send a v2 with that.
Let me know what you think

>
> >
> > Right now, the only camera driver that expose the ACPI location
> > information is the IPU from intel
> > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/media/pci/intel/ipu-bridge.c#n258
> >
> > And they are only using the panel.
> >
> > If we need more information we can consider adding more parameters in
> > the future.

On Thu, Dec 19, 2024 at 6:42 AM Ricardo Ribalda <ribalda@chromium.org> wrote:
>
> On Thu, 19 Dec 2024 at 13:24, Rob Herring <robh@kernel.org> wrote:
> >
> > On Tue, Dec 17, 2024 at 04:24:27PM +0100, Ricardo Ribalda wrote:
> > > Hi Rob
> > >
> > > On Tue, 17 Dec 2024 at 16:02, Rob Herring <robh@kernel.org> wrote:
> > > >
> > > > On Thu, Dec 12, 2024 at 09:44:37PM +0000, Ricardo Ribalda wrote:
> > > > > For some devices like cameras the system needs to know where they are
> > > > > mounted.
> > > >
> > > > Why do you need this and why only this property and not the dozens
> > > > others ACPI has?
> > >
> > > Userspace needs that information to correctly show it in the UI. Eg;
> > >
> > > - User facing camera needs to be mirrored during preview.
> > > - The user facing camera is selected by default during videoconferences
> > > - The world facing camera is selected by default when taking a photo
> > > - User facing camera have different parameter defaults than world facing.
> >
> > We already have "orientation" defined for this purpose.
>
> Do you mean orientation from
> bindings/media/video-interface-devices.yaml ?
>
> I see a couple of issues:
> - Orientation has a very specific meaning for USB typeC. I'd prefer if
> we could avoid using that word.

Yes, but this is tied to the class of the device, not the bus. I find
defining the position for USB devices confusing.

> - For other applications different than cameras it might be useful to
> know the positions top, bottom, left, right, which are not available
> in video-interface-devices

Other devices may need some of the 20 other properties in the ACPI
table as well.

> - The value "external" does not makes too much sense for listed usb devices

Then don't use it.

> - It makes our lives easier if dt and acpi have the same meaning (less
> conversion)

We have little to no input into what ACPI does. If we're just going to
copy ACPI, then just use ACPI instead.

> All that said, for my specific usecase, reusing orientation from
> bindings/media/video-interface-devices.yaml works... So if that is
> what you all prefer I can send a v2 with that.
> Let me know what you think

We already have something for cameras. Use it.

Rob