From: <samu.p.onkalo@nokia.com>
To: <gregkh@suse.de>, <alan@linux.intel.com>
CC: <hmh@hmh.eng.br>, <alan@lxorguk.ukuu.org.uk>, <akpm@linux-foundation.org>,
        <linux-kernel@vger.kernel.org>
Date: Wed, 3 Nov 2010 16:00:20 +0100
Subject: RE: sysfs and power management
Thread-Topic: sysfs and power management
Thread-Index: Act7WIBJDVScD7hwSyOBsh42/gpu2QADyDjw
Message-ID: <62697B07E9803846BC582181BD6FB6B836EB55F0AD@NOK-EUMSG-02.mgdnok.nokia.com>
References: <62697B07E9803846BC582181BD6FB6B836EB2994F4@NOK-EUMSG-02.mgdnok.nokia.com>
 <20101027152809.39701917@lxorguk.ukuu.org.uk>
 <20101029195039.GA26401@suse.de>
 <20101030140047.GA24464@khazad-dum.debian.net>
 <1288526275.2313.14.camel@noppispoppis.nmp.nokia.com>
 <20101031142539.GA25480@suse.de> <1288608087.26073.6.camel@4fid08082>
 <20101101165701.2fc30368@linux.intel.com> <20101101180740.GA17148@suse.de>
 <20101103094452.0cfae4ec@linux.intel.com> <20101103130925.GA15885@suse.de>
In-Reply-To: <20101103130925.GA15885@suse.de>
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>-----Original Message-----
>From: ext Greg KH [mailto:gregkh@suse.de]
>Sent: 03 November, 2010 15:09
>To: Alan Cox
>Cc: Onkalo Samu.P (Nokia-MS/Tampere); ext Henrique de Moraes Holschuh;
>Alan Cox; akpm@linux-foundation.org; linux-kernel@vger.kernel.org
>Subject: Re: sysfs and power management
>
>On Wed, Nov 03, 2010 at 09:44:52AM +0000, Alan Cox wrote:
>> On Mon, 1 Nov 2010 11:07:40 -0700
>> Greg KH <gregkh@suse.de> wrote:
>>
>> > On Mon, Nov 01, 2010 at 04:57:01PM +0000, Alan Cox wrote:
>> > > > I took a look to that. It seems that iio is more or less sysfs
>> > > > based. There are ring buffers and event device which are chardev
>> > > > based but still the data outside ring buffer and the control is
>> > > > sysfs based.
>> > >
>> > > IIO is sysfs dependant, heavyweight and makes no sense for some of
>> > > the sysfs based drivers. IIO is also staging based and Linus
>> > > already threw out the last attempt to unify these drivers sanely
>> > > with an ALS layer - which was smaller, cleaner and better !
>> >
>> > I think we need to revisit this issue again, before iio is merged to
>> > the main kernel tree.  I've been totally ignoring the iio
>user/kernel
>> > api at the moment, waiting for things to settle down there
>>
>> Actually I think there is another way to do it cleanly
>>
>> Keep a flag per device (or per runtime pm struct of device)
>>
>> And on the open/close do
>>
>> 	if (runtime_pm on device && device has SYSFS_PM set)
>> 		pm_runtime_foo
>>
>> so that devices that need to be powered up to handle sysfs requests
>can
>> set a single flag and just work.
>
>That sounds like a reasonable idea.
>

I'm working with the implementation which adds possibility to add per attribute
open_close_notification method with minimal overhead to current system.

-Samu


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