From mboxrd@z Thu Jan 1 00:00:00 1970 From: Matthew Garrett Subject: Re: Run-time PM idea (was: Re: [RFC][PATCH 0/2] PM: Rearrange core suspend code) Date: Mon, 8 Jun 2009 16:11:56 +0100 Message-ID: <20090608151156.GA17805__5981.48457143015$1244473975$gmane$org@srcf.ucam.org> References: <20090608131159.GA15100@srcf.ucam.org> <20090608132235.GC13214@elte.hu> <200906081539.20459.oliver@neukum.org> <20090608142154.GD14234@elte.hu> <20090608143023.GA16752@srcf.ucam.org> <20090608150603.GB20905@elte.hu> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <20090608150603.GB20905@elte.hu> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: linux-pm-bounces@lists.linux-foundation.org Errors-To: linux-pm-bounces@lists.linux-foundation.org To: Ingo Molnar Cc: LKML , ACPI Devel Maling List , pm list List-Id: linux-pm@vger.kernel.org On Mon, Jun 08, 2009 at 05:06:03PM +0200, Ingo Molnar wrote: > But if you think that tracking the usage state of the hardware is > 'complexity', then you very much dont know what you are talking > about. The main task of the kernel is to track hardware usage and to > abstract away the fact that the same hardware is used by multiple > tasks, and to do it safely. It's what the kernel does all day. What I'm saying is that you don't *know* what the usage state of the hardware is, and in many cases you can't know. A given user may be happy to sacrifice their SATA hotplug support. Another with identical hardware may not. A given network application may be mission critical and intolerant of the network interface being shut down. The same application in a different context may not. We'd need to provide a bewildering array of interfaces to distinguish between these situations, and we'd be unable to turn on autosuspend until the entirity of userspace had been ported to them. -- Matthew Garrett | mjg59@srcf.ucam.org