linux-kernel - Re: [RFC PATCH] device-core: sysfs open

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Message-ID: <AANLkTikRSF-4o=Jnyg2_Wa4gg7E+s_tM9ZD3g+f7hyWm@mail.gmail.com>
Date:	Mon, 1 Nov 2010 00:14:04 +0800
From:	Ming Lei <tom.leiming@...il.com>
To:	Samu Onkalo <samu.p.onkalo@...ia.com>
Cc:	gregkh@...e.de, hmh@....eng.br, alan@...ux.intel.com,
	akpm@...ux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH] device-core: sysfs open - close notify

2010/10/31 Samu Onkalo <samu.p.onkalo@...ia.com>:
> Device drivers have no idea when somebody in userspace keeps some sysfs entry
> open. The driver just received read or write calls. The driver may want to
> control HW state based on activity so it either have to turn HW on and off
> for each sysfs access or it needs separate enable disable entry which controls
> the HW state. In cases where sysfs is used to pass some events under interrupt
> control (like proximity events from the proximity sensors) it is not enough to
> just keep sysfs entry open in userspace.

Since very few drivers have this kind of requirement, why not take notifier
call chain mechanism to do such thing? eg. register a notifier function
if the driver is interested in such kind of open/close events.

Your patch may cause many unnecessary memory waste because
most of drivers does not need attribute file .open/.close notifier.


thanks,
-- 
Lei Ming
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