Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755381Ab3JBSnM (ORCPT ); Wed, 2 Oct 2013 14:43:12 -0400 Received: from mail-pd0-f172.google.com ([209.85.192.172]:43896 "EHLO mail-pd0-f172.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754057Ab3JBSnK (ORCPT ); Wed, 2 Oct 2013 14:43:10 -0400 Date: Wed, 2 Oct 2013 11:43:30 -0700 From: Christoffer Dall To: Scott Wood Cc: Yoder Stuart-B08248 , Alex Williamson , Kim Phillips , "gregkh@linuxfoundation.org" , "linux-kernel@vger.kernel.org" , "a.motakis@virtualopensystems.com" , "agraf@suse.de" , Wood Scott-B07421 , Sethi Varun-B16395 , Bhushan Bharat-R65777 , "peter.maydell@linaro.org" , "santosh.shukla@linaro.org" , "kvm@vger.kernel.org" Subject: Re: RFC: (re-)binding the VFIO platform driver to a platform device Message-ID: <20131002184330.GC5108@cbox> References: <20131001133831.6e46e8e00e09d5d9079fde57@linaro.org> <20131001200054.GA27330@kroah.com> <20131001170244.ff4fb81d9a7a09598c4c6247@linaro.org> <20131002015355.GD63102@lvm> <1380681356.14271.57.camel@ul30vt.home> <20131002151413.GG63102@lvm> <9F6FE96B71CF29479FF1CDC8046E15036D405D@039-SN1MPN1-003.039d.mgd.msft.net> <1380738758.12932.43.camel@snotra.buserror.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1380738758.12932.43.camel@snotra.buserror.net> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3160 Lines: 69 On Wed, Oct 02, 2013 at 01:32:38PM -0500, Scott Wood wrote: > On Wed, 2013-10-02 at 13:25 -0500, Yoder Stuart-B08248 wrote: > > > > > -----Original Message----- > > > From: Christoffer Dall [mailto:christoffer.dall@linaro.org] > > > Sent: Wednesday, October 02, 2013 10:14 AM > > > To: Alex Williamson > > > Cc: Kim Phillips; gregkh@linuxfoundation.org; linux- > > > kernel@vger.kernel.org; a.motakis@virtualopensystems.com; agraf@suse.de; > > > Yoder Stuart-B08248; Wood Scott-B07421; Sethi Varun-B16395; Bhushan > > > Bharat-R65777; peter.maydell@linaro.org; santosh.shukla@linaro.org; > > > kvm@vger.kernel.org > > > Subject: Re: RFC: (re-)binding the VFIO platform driver to a platform > > > device > > > > > > Wouldn't a sysfs file to add compatibility strings to the vfio-platform > > > driver make driver_match_device return true and make everyone happy? > > > > I had a similar thought. Why can't we do something like: > > > > echo "fsl,i2c" > /sys/bus/platform/drivers/vfio-platform/new_compatible > > echo 12ce0000.i2c > /sys/bus/platform/drivers/vfio-platform/bind > > > > The first steps tell vfio-platform to register itself to handle > > "fsl,i2c" compatible devices. The second step does the bind. > > Needing to specify the compatible is hacky (we already know what device > we want to bind; why do we need to scrounge up more information than > that, and add a new sysfs interface for extending compatible matches, > and a more flexible data structure to back that up?), and is racy on > buses that can hotplug (which driver gets the new device?). Why hacky? It seems quite reasonable to me that the user has to tell a subsystem that from a certain point it should be capable of handling some device. As for the data structure, isn't this a simple linked list? The problem with the race seems to be a common problem that hasn't even been solved for PCI yet, so I'm wondering if this is not an orthogonal issue with a separate solution, such as a priority or something like that. Yes, once you've added the new_compatible to the vfio-platform driver, it's up for grabs from both the new and the old driver, but that could be solved by always making sure that the vfio-platform driver is checked first. (I'm not familiar with these data structures, but I would imagine something like re-inserting the vfio-platform driver in the list/tree/... whenever adding a new_compatible value might possibly be one solution). > > What's wrong with a non-vfio-specific flag that a driver can set, that > indicates that the driver is willing to try to bind to any device on the > bus if explicitly requested via the existing sysfs bind mechanism? > It sounds more hackish to me to invent some 'generic' flag to solve a very specific case. What you're suggesting would let users specify that a serial driver should handle a NIC hardware, no? That sounds much much worse to me. -Christoffer -- 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/