From: Oliver Neukum <oliver@neukum.org>
To: Pavel Machek <pavel@ucw.cz>
Subject: Re: [RFD] Automatic suspend
Date: Mon, 2 Mar 2009 09:24:36 +0100
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Cc: "Arve Hj?nnev?g" <arve@android.com>, "Rafael J. Wysocki" <rjw@sisk.pl>,
       Alan Stern <stern@rowland.harvard.edu>,
       "Woodruff, Richard" <r-woodruff2@ti.com>,
       Arjan van de Ven <arjan@infradead.org>,
       Kyle Moffett <kyle@moffetthome.net>,
       Benjamin Herrenschmidt <benh@kernel.crashing.org>,
       pm list <linux-pm@lists.linux-foundation.org>,
       LKML <linux-kernel@vger.kernel.org>,
       Nigel Cunningham <nigel@nigel.suspend2.net>,
       Matthew Garrett <mjg59@srcf.ucam.org>,
       mark gross <mgross@linux.intel.com>, Uli Luckas <u.luckas@road.de>,
       Igor Stoppa <igor.stoppa@nokia.com>,
       Brian Swetland <swetland@google.com>, Len Brown <lenb@kernel.org>
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Am Sonntag 01 M?rz 2009 23:56:47 schrieb Pavel Machek:
> > Allowing user space to suspend input devices while they are still open
> > is useful. The user-space code that reads from the input devices does
> > not need to know if the device is suspended or not, and the kernel
> > cannot auto suspend input devices based on inactivity.
>
> Actually, I'd like you to fix your userspace and close input devices
> when it does not need them. Given the way you control the platform it
> should not be that hard. I do not see why we'd want to invent new
> interface for "uhuh, I have opened the keyboard but I am not really
> interested in keys being pressed".

Generally you can't do this. A task has an open fd.

- you cannot assume it can open the device again (fd may be inherited)
- keeping the device open makes sure you are talking to the same device
- you may want to avoid repeating expensive initialisations
- some input devices also do output

	Regards
		Oliver

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