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

From: Pavel Machek <pavel@ucw.cz>
To: Jacek Anaszewski <jacek.anaszewski@gmail.com>
Cc: "Alan Stern" <stern@rowland.harvard.edu>,
	"Jacek Anaszewski" <j.anaszewski@samsung.com>,
	"Rafał Miłecki" <zajec5@gmail.com>,
	"Richard Purdie" <rpurdie@rpsys.net>,
	"Felipe Balbi" <balbi@kernel.org>,
	"Greg KH" <gregkh@linuxfoundation.org>,
	"Peter Chen" <hzpeterchen@gmail.com>,
	"linux-usb@vger.kernel.org" <linux-usb@vger.kernel.org>,
	"Rafał Miłecki" <rafal@milecki.pl>,
	"Jonathan Corbet" <corbet@lwn.net>,
	"Ezequiel Garcia" <ezequiel@vanguardiasur.com.ar>,
	"Stephan Linz" <linz@li-pro.net>,
	"Matthias Brugger" <mbrugger@suse.com>,
	"Boris Brezillon" <boris.brezillon@free-electrons.com>,
	"Geert Uytterhoeven" <geert@linux-m68k.org>,
	"open list:DOCUMENTATION" <linux-doc@vger.kernel.org>,
	"open list" <linux-kernel@vger.kernel.org>, "open list":;
Subject: Re: [PATCH RFC V3.5] leds: trigger: Introduce an USB port trigger
Date: Fri, 26 Aug 2016 21:50:34 +0200	[thread overview]
Message-ID: <20160826195034.GC21442@amd> (raw)
In-Reply-To: <57BF3D64.3090402@gmail.com>

On Thu 2016-08-25 20:48:04, Jacek Anaszewski wrote:
> 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.

Actually, they don't. They identify device _type_. If you have two
mice of the same type connected, they'll have same idProduct /
idVendor values.

									Pavel
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