linux-kernel - Re: [RESEND][PATCH 1/2] dt-bindings: usb: add non-removable-ports hub property

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Date:   Mon, 27 Jan 2020 16:56:15 +0000
From:   Måns Rullgård <mans@...sr.com>
To:     Rob Herring <robh@...nel.org>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Mark Rutland <mark.rutland@....com>, linux-usb@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RESEND][PATCH 1/2] dt-bindings: usb: add non-removable-ports hub property

Rob Herring <robh@...nel.org> writes:

> On Fri, Jan 24, 2020 at 03:25:03PM +0000, Mans Rullgard wrote:
>> Add a non-removable-ports property that lists the hardwired downstream
>> ports of a hub.  Although hubs can provide this information, they are
>> not always configured correctly.  An alternate means of indicating this
>> for built-in USB devices is thus useful.
>> 
>> Signed-off-by: Mans Rullgard <mans@...sr.com>
>
> I reviewed this already, but since you didn't add my reviewed-by, I'm 
> looking at it again and having 2nd thoughts.
>
>> ---
>>  Documentation/devicetree/bindings/usb/usb-device.txt | 4 ++++
>>  1 file changed, 4 insertions(+)
>> 
>> diff --git a/Documentation/devicetree/bindings/usb/usb-device.txt b/Documentation/devicetree/bindings/usb/usb-device.txt
>> index 036be172b1ae..92d863cc96b6 100644
>> --- a/Documentation/devicetree/bindings/usb/usb-device.txt
>> +++ b/Documentation/devicetree/bindings/usb/usb-device.txt
>> @@ -66,6 +66,10 @@ Required properties for host-controller nodes with device nodes:
>>  - #size-cells: shall be 0
>>  
>>  
>> +Optional properties for hub and host-controller nodes:
>> +- non-removable-ports: list of hardwired downstream ports
>
> If you have a hardwired device and need to know that, doesn't that imply 
> there's some other stuff you need to describe beyond what a standard USB 
> device has. Such as a power supply that's not Vbus from the hub.

I suppose there could be, but there isn't in my actual situation.

> At a minimum, I think this should be a per port property.

That's what I suggested first.  Greg told me to do it like this instead.

> Though really, I think this should just be implied by describing the
> device in DT. I'm not sure if there's a case for hotpluggable devices
> described in DT.  Maybe with overlays.

That's also an option.  Greg, what do you think?

-- 
Måns Rullgård