From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753395AbbETJDv (ORCPT ); Wed, 20 May 2015 05:03:51 -0400 Received: from mail-qg0-f48.google.com ([209.85.192.48]:36820 "EHLO mail-qg0-f48.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753213AbbETJDp (ORCPT ); Wed, 20 May 2015 05:03:45 -0400 MIME-Version: 1.0 In-Reply-To: References: <1432044679-10256-3-git-send-email-tomeu.vizoso@collabora.com> From: Tomeu Vizoso Date: Wed, 20 May 2015 11:03:23 +0200 X-Google-Sender-Auth: NflcIPl23uepBO8xdsgUKpEzyJ8 Message-ID: Subject: Re: [PATCH v3 2/2] PM / Runtime: Add pm_runtime_enable_recursive To: Alan Stern Cc: "linux-pm@vger.kernel.org" , Laurent Pinchart , Dmitry Torokhov , "Rafael J. Wysocki" , Len Brown , Pavel Machek , Greg Kroah-Hartman , Ulf Hansson , Kevin Hilman , Russell King , Krzysztof Kozlowski , "linux-kernel@vger.kernel.org" Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 19 May 2015 at 19:49, Alan Stern wrote: > On Tue, 19 May 2015, Tomeu Vizoso wrote: > >> This function makes less cumbersome to enable runtime PM in a device and >> its descendants. >> >> Signed-off-by: Tomeu Vizoso > > I don't see the point of this. In the scenario you have in mind, are > the device and all its descendants registered by the same > subsystem/driver? Not quite, the scenario here is a driver (uvcvideo) that deals with a specific piece of hardware and knows that all the descendants of the device it's bound to are virtual. The subtree is: 1-1:1.0 (bound to uvcvideo) ep_87 input4 event4 media0 video0 I liked how the force_direct_complete flag played out here, but I agree with Rafael that it can be abused as the PM domain or the bus type weren't able to prevent going directly to complete. This is my testing branch, btw: https://git.collabora.com/cgit/user/tomeu/linux.git/log/?h=fast-resume-v5 > If they are, can't the subsystem/driver code enable > runtime PM for each of them when they are registered, by adding a > single call in the right spot? > > If they don't all belong to the same subsystem/driver, who is going to > call your pm_runtime_enable_recursive routine? No single caller will > have the right to enable runtime PM for all these devices. Yeah, I was thinking that uvcvideo might be able to decide that, but I'm not really sure about it. Thanks, Tomeu > Alan Stern > > -- > 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/