Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756629AbZKRKJO (ORCPT ); Wed, 18 Nov 2009 05:09:14 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754031AbZKRKJN (ORCPT ); Wed, 18 Nov 2009 05:09:13 -0500 Received: from mail-yw0-f202.google.com ([209.85.211.202]:42347 "EHLO mail-yw0-f202.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752280AbZKRKJM (ORCPT ); Wed, 18 Nov 2009 05:09:12 -0500 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type; b=RweyBxZztrnbQcVF3PRqW0ygqsFCc6qPLOCJKB9ecjqw8MOltcj7HV+I45zBFGYaIW +l+0Ult9cz0MPyS33nGeXCOk+4XobPrHiyFndq/B+QFBZjIK6IeTK4vbiuICMVPcUf0u 5UtleGjzhnmfHECxIOrULfqKlEigzzG2A4HjU= MIME-Version: 1.0 In-Reply-To: <20091117125901.GF823@rakim.wolfsonmicro.main> References: <20091109105858.GB1245@sirena.org.uk> <20091109133136.GC1245@sirena.org.uk> <20091116153000.GB29479@sirena.org.uk> <20091117125901.GF823@rakim.wolfsonmicro.main> Date: Wed, 18 Nov 2009 19:09:14 +0900 Message-ID: Subject: Re: Null suspend/resume functions From: Magnus Damm To: Mark Brown Cc: Kuninori Morimoto , alsa-devel@alsa-project.org, linux-pm@lists.linux-foundation.org, Magnus Damm , linux-kernel@vger.kernel.org Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2409 Lines: 52 On Tue, Nov 17, 2009 at 9:59 PM, Mark Brown wrote: > On Tue, Nov 17, 2009 at 09:46:35PM +0900, Magnus Damm wrote: > >> On SuperH we have Runtime PM enabled on a few platforms together with >> a few updated drivers. The latest driver to become more power aware is >> this FSI driver. > > I understand exactly what the runtime PM stuff and the driver are doing > here, the issue is the mandatory suspend and resume functions. Cool, but don't you think it makes sense to see how other architectures will deal with this first? >> At this point the SuperH specific platform bus code requires the >> callbacks ->runtime_suspend() and ->runtime_resume() to be present. It >> may be a good idea to allow them to be NULL in the future or maybe >> having some shared functions, but before starting to break out stuff >> I'd like to see how other Runtime PM implementations deal with this. >> So unless people object I prefer to keep it as-is for now. > > What is the reason for requiring that the driver provide stub functions? > For me the issue is that if it's mandatory for the driver to provide the > functions then having stub functions in there makes the driver look like > it is abusing the API by not implementing mandatory functionality. I see your point, but there is another side to it as well. Having the stubs there is a way of showing that these functions may be called as part of the Runtime PM management. Not having them would confuse people even more IMO. > Given that the arch is now dealing with clocking and power for the > device using the runtime PM system it seems fairly clear that there are > going to be drivers like this one that can at least skip the suspend > part and may not need to do anything at resume time either. Right. We just need to figure out what the arch-independent solution would be, and we're unfortunately not there yet. I can spend some time on updating the drivers and removing the nop-stubs if you'd like, but I'd rather not since I suspect that I'll have to update things again when we get Runtime PM for ARM or other non-sh architectures. Let me know what you think! / magnus -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/