Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752016AbXBKNKU (ORCPT ); Sun, 11 Feb 2007 08:10:20 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752674AbXBKNKU (ORCPT ); Sun, 11 Feb 2007 08:10:20 -0500 Received: from 1wt.eu ([62.212.114.60]:2338 "EHLO 1wt.eu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752016AbXBKNKT (ORCPT ); Sun, 11 Feb 2007 08:10:19 -0500 Date: Sun, 11 Feb 2007 14:09:43 +0100 From: Willy Tarreau To: Matthew Garrett Cc: "Rafael J. Wysocki" , Daniel Barkalow , nigel@nigel.suspend2.net, Robert Hancock , linux-kernel , Jeff Garzik , Pavel Machek , pm list Subject: Re: [PATCH] Re: NAK new drivers without proper power management? Message-ID: <20070211130943.GA1868@1wt.eu> References: <200702101130.44471.rjw@sisk.pl> <200702102050.28218.rjw@sisk.pl> <20070211065404.GA943@1wt.eu> <20070211121339.GB4204@srcf.ucam.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20070211121339.GB4204@srcf.ucam.org> User-Agent: Mutt/1.5.11 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1717 Lines: 33 On Sun, Feb 11, 2007 at 12:13:40PM +0000, Matthew Garrett wrote: > On Sun, Feb 11, 2007 at 07:54:04AM +0100, Willy Tarreau wrote: > > > instead of modifying all drivers to explicitly state that they don't support > > it, we should start with a test of the NULL pointer for .suspend which should > > mean exactly the same without modifying the drivers. I find it obvious that > > a driver which does provide a suspend function will not support it. And if > > some drivers (eg /dev/null) can support it anyway, it's better to change > > *those* drivers to explicitly mark them as compatible. > > No, that doesn't work. In the absence of suspend/resume methods, the PCI > layer will implement basic PM itself. In some cases, this works. In > others, it doesn't. There's no way to automatically determine which is > which without modifying the drivers. Then change the PCI layer to do the basic PM only for known compatible drivers, and modify only the known-compatible drivers to mark them explicitly compatible. IMHO, it generally is a bad idea to require that any driver explicitly states what it *does not* support. It's the reason why users encounter problem on new features with old drivers. For instance, do you know if the old ISA NE2000 driver breaks suspend ? I don't know, but I would at least expect it not to support it by default. It's best to announce what *is* supported and consider everything unimplemented otherwise explicitly stated. Regards, Willy - 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/