From mboxrd@z Thu Jan 1 00:00:00 1970 From: Nigel Cunningham Subject: Re: [PATCH] Re: NAK new drivers without proper power management? Date: Mon, 12 Feb 2007 09:49:05 +1100 Message-ID: <1171234145.4493.91.camel@nigel.suspend2.net> References: <200702101130.44471.rjw@sisk.pl> <200702102050.28218.rjw@sisk.pl> <20070211065404.GA943@1wt.eu> <20070211121339.GB4204@srcf.ucam.org> Reply-To: nigel@nigel.suspend2.net Mime-Version: 1.0 Content-Type: text/plain Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20070211121339.GB4204@srcf.ucam.org> Sender: linux-kernel-owner@vger.kernel.org To: Matthew Garrett Cc: Willy Tarreau , "Rafael J. Wysocki" , Daniel Barkalow , Robert Hancock , linux-kernel , Jeff Garzik , Pavel Machek , pm list List-Id: linux-pm@vger.kernel.org Hi. On Sun, 2007-02-11 at 12:13 +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. I think we have it backwards there. Power management support for a driver should always start with the driver itself. If there's a generic routine that can be used for the bus, the driver should explicitly set the routine to the generic routine. Regards, Nigel