linux-kernel - Re: [PATCH V2 PROOF OF CONCEPT 2/1] trigger: ledtrig-usbport: read initial state from DT

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Date:	Wed, 13 Jul 2016 17:05:32 +0200
From:	Rafał Miłecki <zajec5@...il.com>
To:	Jacek Anaszewski <j.anaszewski@...sung.com>
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
	"open list:LED SUBSYSTEM" <linux-leds@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	Richard Purdie <rpurdie@...ys.net>,
	open list <linux-kernel@...r.kernel.org>,
	Rob Herring <robh+dt@...nel.org>,
	Mark Rutland <Mark.Rutland@....com>,
	Felipe Balbi <balbi@...nel.org>
Subject: Re: [PATCH V2 PROOF OF CONCEPT 2/1] trigger: ledtrig-usbport: read
 initial state from DT

On 13 July 2016 at 16:48, Jacek Anaszewski <j.anaszewski@...sung.com> wrote:
> On 07/13/2016 02:42 PM, Rafał Miłecki wrote:
>>
>> This allows specifying USB ports that should be observed by a trigger
>> right after activating it. Example:
>>
>> usb {
>>         gpios = <&gpio 0 GPIO_ACTIVE_HIGH>;
>>         linux,default-trigger = "usbport";
>>         usb-controllers = <&ohci>, <&ehci>, <&xhci USB_HCD_SHARED>;
>>         usb-ports = "1", "1", "1";
>
>
> Port is a numerical value, right?
> Wouldn't it be better to define it as an array of integers?
>
> e.g.: usb-ports = <1>. <1>, <1>;

Not always. Let me quote this part of "usbport" documentation:

> This also allows handling devices with internal hubs (when root hub's port has
> always a device (hub) connected). User can simply specify specify internal hub
> ports then (e.g. 1-1.1, 1-1.2, etc.).

In such case we'd need usb-ports = "1.1", "1.2";

Anyway, there is a discussion ongoing in:
[PATCH V2 0/1] usb: add HCD providers
so let's see if someone will have a better idea for referencing USB
ports inside DT.