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

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Message-ID: <20160829084127.GA10529@amd>
Date:   Mon, 29 Aug 2016 10:41:27 +0200
From:   Pavel Machek <pavel@....cz>
To:     Rafał Miłecki <zajec5@...il.com>
Cc:     Jacek Anaszewski <j.anaszewski@...sung.com>,
        Jacek Anaszewski <jacek.anaszewski@...il.com>,
        Alan Stern <stern@...land.harvard.edu>,
        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>
Subject: Re: [PATCH RFC V3.5] leds: trigger: Introduce an USB port trigger

On Mon 2016-08-29 10:21:48, Rafał Miłecki wrote:
> On 29 August 2016 at 10:05, Pavel Machek <pavel@....cz> wrote:
> >> >2) Having "ports" subdir with RW files, one per each existing physical port
> >> >In this situation we don't need "new_port" or "remove_port". If we
> >> >want port to be observable we just do:
> >> >echo 1 > 1-1
> >> >Implementing this solution needs reading more details from USB subsystem.
> >>
> >> The situation here is clear IMO - the number of USB ports in the system
> >> can change dynamically. I'm not sure if this can be handled easily with
> >> sysfs, where we usually expose an interface for known set of settings.
> >> struct attribute arrays are usually defined statically at the compile
> >> time and filled with the variables, that are created with DEVICE_ATTR
> >> macro.
> >
> > sysfs already exposes current view of all usb devices. Just use it.
> 
> We're talking about USB ports not devices, but this is still true. You
> can find them in
> /sys/bus/usb/devices/*/*-port*
> 
> I can't see how we could use them. How could I develop sysfs interface
> in /sys/class/leds/*/ to allow userspace assigning USB ports to the
> LED trigger?

Create /sys/bus/usb/devices/*/*-port*/led_trigger file?

(Do you plan one USB trigger, or multiple ones?)
									Pavel

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