linux-kernel - Re: [PATCH v2] leds: triggers: send uevent when changing triggers

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Message-ID: <20120807205631.GA3889@kroah.com>
Date:	Tue, 7 Aug 2012 13:56:31 -0700
From:	Greg KH <gregkh@...uxfoundation.org>
To:	Colin Cross <ccross@...roid.com>
Cc:	linux-kernel@...r.kernel.org,
	Henrique de Moraes Holschuh <hmh@....eng.br>,
	Bryan Wu <bryan.wu@...onical.com>,
	Richard Purdie <rpurdie@...ys.net>, linux-leds@...r.kernel.org
Subject: Re: [PATCH v2] leds: triggers: send uevent when changing triggers

On Tue, Aug 07, 2012 at 01:47:23PM -0700, Colin Cross wrote:
> On Tue, Aug 7, 2012 at 1:42 PM, Greg KH <gregkh@...uxfoundation.org> wrote:
> > On Tue, Aug 07, 2012 at 12:58:15PM -0700, Colin Cross wrote:
> >> Some triggers create sysfs files when they are enabled.  Send a uevent
> >> "change" notification whenever the trigger is changed to allow userspace
> >> processes such as udev to modify permissions on the new files.
> >>
> >> A change notification will also be sent during registration of led class
> >> devices or led triggers if the default trigger of an led class device
> >> is found.
> >
> > Why would a change event be needed at this point in time?  Nothing would
> > have changed from the original "add" notification, right?
> 
> If the led class device has a default trigger configured,
> device_create will called before the trigger has been set and the
> trigger sysfs files have been created.  The "change" notification will
> happen after the extra files have been created.

Ok, that make sense, and is a good reason to send the change event,
thanks for explaining it.

greg k-h
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