On 15/03/18 13:46, Robin Murphy wrote:

On 12/03/18 10:41, Roger Quadros wrote:
[...]

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+USB Connector
+=============
+
+USB connector node represents physical USB connector. It should be
+a child of USB interface controller.
+
+Required properties:
+- compatible: describes type of the connector, must be one of:
+??? "usb-a-connector",
+??? "usb-b-connector",
+??? "usb-c-connector".

compatible should be just "usb-connector"

Type should be a property

type: type of usb connector "A", "B", "AB", "C"
AB is for dual-role connectors.

I have proposed such property (and size also) in my first RFC [1]. Rod
did not like it :)

[1]: https://marc.info/?l=devicetree&m=150660411515233&w=2

This is what Rob says here https://patchwork.kernel.org/patch/9976043/
"We did "type" for hdmi-connector, but I think I'd really prefer
compatible be used to distinguish as least where it may matter to s/w.
In the HDMI case, they all are pretty much the same, just different
physical size."

So the question is. Does it matter to this particular software implementation
if it is type A,B,C connector?
If yes, how?

Type A will never have any alternate function. It is always dedicated to USB.

In USB spec terms, at least. In reality there are things like the cool trick Rockchip SoCs do whereby they can expose the debug UART Rx/Tx through the OTG port's D+/D- pins, and that is on a type A connector in many products. I'm guessing that's probably beyond the scope of this binding, though.

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Also does the size "full", "micro", "mini" matter to software?

If it means the user can look in sysfs to easily correlate logical ports with physical connectors that's certainly handy (e.g. on something like Odroid-XU where the two USB3 ports are brought out to an A and a micro-AB connector respectively).

But this logic fails if both connectors are the same type/size.
This is where the label comes in handy. The labels can be unique and end user can identify the port using that.

Robin.

-- 
cheers,
-roger

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