linux-kernel - Re: [PATCH RFC V3.5] leds: trigger: Introduce an USB port trigger

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Date:   Thu, 25 Aug 2016 20:48:04 +0200
From:   Jacek Anaszewski <jacek.anaszewski@...il.com>
To:     Alan Stern <stern@...land.harvard.edu>,
        Jacek Anaszewski <j.anaszewski@...sung.com>
Cc:     Rafał Miłecki <zajec5@...il.com>,
        Richard Purdie <rpurdie@...ys.net>,
        Felipe Balbi <balbi@...nel.org>,
        Greg KH <gregkh@...uxfoundation.org>,
        Peter Chen <hzpeterchen@...il.com>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        Rafał Miłecki <rafal@...ecki.pl>,
        Jonathan Corbet <corbet@....net>,
        Ezequiel Garcia <ezequiel@...guardiasur.com.ar>,
        Stephan Linz <linz@...pro.net>,
        Matthias Brugger <mbrugger@...e.com>,
        Boris Brezillon <boris.brezillon@...e-electrons.com>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        "open list:DOCUMENTATION" <linux-doc@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>,
        "open list:LED SUBSYSTEM" <linux-leds@...r.kernel.org>,
        Pavel Machek <pavel@....cz>
Subject: Re: [PATCH RFC V3.5] leds: trigger: Introduce an USB port trigger

On 08/25/2016 04:30 PM, Alan Stern wrote:
> On Thu, 25 Aug 2016, Jacek Anaszewski wrote:
>
>> I'd see it as follows:
>>
>> #cat available_ports
>> #1-1 1-2 2-1
>>
>> #echo "1-1" > new_port
>>
>> #cat observed_ports
>> #1-1
>>
>> #echo "2-1" > new_port
>>
>> #cat observed_ports
>> #1-1 2-1
>>
>> We've already had few discussions about the sysfs designs trying
>> to break the one-value-per-file rule for LED class device, and
>> there was always strong resistance against.
>
> This scheme has multiple values in both the available_ports and
> observed_ports files.  :-(  Not that I have any better suggestions...

Right, I forgot to add a note here, that this follows space
separated list pattern similarly as in case of triggers attribute.
Of course other suggestions are welcome.

>>>> Also a description of the device connected to the port would be a nice
>>>> feature, however I am not certain about the feasibility thereof.
>>>
>>> What kind of description do you mean? Where should it be used / where
>>> should it appear?
>>>
>>
>> Product name/symbol. Actually it should be USB subsystem responsibility
>> to provide the means for querying the product name by port id, if it
>> is possible at all.
>
> 	cat /sys/bus/usb/devices/PORT/product
> 	cat /sys/bus/usb/devices/PORT/manufacturer
>
> These will work if there is a device registered under PORT.

I've found only idProduct and idVendor files. They indeed uniquely
identify the device, but the numbers are not human readable.
Is there a way to retrieve the corresponding names in kernel?
Does the lsusb command do the mapping in the user space or maybe
it takes the names from kernel?

-- 
Best regards,
Jacek Anaszewski