From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932959Ab3LIS6H (ORCPT ); Mon, 9 Dec 2013 13:58:07 -0500 Received: from mail-oa0-f51.google.com ([209.85.219.51]:33201 "EHLO mail-oa0-f51.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932251Ab3LIS6F (ORCPT ); Mon, 9 Dec 2013 13:58:05 -0500 Date: Mon, 9 Dec 2013 12:58:02 -0600 From: Kim Phillips To: scottwood@freescale.com Cc: jan.kiszka@siemens.com, linux-kernel@vger.kernel.org, gregkh@linuxfoundation.org, kvm@vger.kernel.org, R65777@freescale.com, B07421@freescale.com, B08248@freescale.com, christoffer.dall@linaro.org, alex.williamson@redhat.com, a.motakis@virtualopensystems.com, agraf@suse.de, B16395@freescale.com Subject: Re: [REPOST][PATCH 1/2] driver core: Add new device_driver flag to allow binding via sysfs only Message-Id: <20131209125802.0e2b86a3daa9d9ad5a7d43bf@linaro.org> In-Reply-To: <1386283095.7375.63.camel@snotra.buserror.net> References: <20131203123446.42fbff34a8ebd7afd38159a5@linaro.org> <529DFA09.1030707@siemens.com> <20131205174530.a1d6e763e423d3baaa5992ad@linaro.org> <1386283095.7375.63.camel@snotra.buserror.net> X-Mailer: Sylpheed 3.4.0beta5 (GTK+ 2.24.20; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 5 Dec 2013 16:38:15 -0600 Scott Wood wrote: > On Thu, 2013-12-05 at 17:45 +0000, Kim Phillips wrote: > > On Tue, 03 Dec 2013 16:34:33 +0100 > > Jan Kiszka wrote: > > > > > On 2013-12-03 13:34, Kim Phillips wrote: > > > > VFIO supports pass-through of devices to user space - for sake > > > > of illustration, say a PCI e1000 device: > > > > > > > > - the e1000 is first unbound from the PCI e1000 driver via sysfs > > > > - the vfio-pci driver is told via new_id that it now handles e1000 devices > > > > - the e1000 is explicitly bound to vfio-pci through sysfs > > > > > > > > However, now we have two drivers in the system that both handle e1000 > > > > devices. A hotplug event could then occur and it is ambiguous as to which > > > > driver will claim the device. The desired semantics is that vfio-pci is > > > > only bound to devices by explicit request in sysfs. This patch makes this > > > > possible by introducing a sysfs_bind_only flag in struct device_driver. > > > > > > > > Signed-off-by: Stuart Yoder > > > > Signed-off-by: Kim Phillips > > > > --- > > > > rebased onto 3.13-rc2, and reposted from first submission which > > > > recieved no comments: > > > > > > > > https://lkml.org/lkml/2013/10/11/53 > > > > > > > > drivers/base/dd.c | 5 ++++- > > > > include/linux/device.h | 2 ++ > > > > 2 files changed, 6 insertions(+), 1 deletion(-) > > > > > > > > diff --git a/drivers/base/dd.c b/drivers/base/dd.c > > > > index 0605176..b83b16d 100644 > > > > --- a/drivers/base/dd.c > > > > +++ b/drivers/base/dd.c > > > > @@ -389,7 +389,7 @@ static int __device_attach(struct device_driver *drv, void *data) > > > > { > > > > struct device *dev = data; > > > > > > > > - if (!driver_match_device(drv, dev)) > > > > + if (drv->sysfs_bind_only || !driver_match_device(drv, dev)) > > > > return 0; > > > > > > > > return driver_probe_device(drv, dev); > > > > @@ -476,6 +476,9 @@ static int __driver_attach(struct device *dev, void *data) > > > > */ > > > > int driver_attach(struct device_driver *drv) > > > > { > > > > + if (drv->sysfs_bind_only) > > > > + return 0; > > > > + > > > > return bus_for_each_dev(drv->bus, NULL, drv, __driver_attach); > > > > } > > > > EXPORT_SYMBOL_GPL(driver_attach); > > > > diff --git a/include/linux/device.h b/include/linux/device.h > > > > index 952b010..ed441d1 100644 > > > > --- a/include/linux/device.h > > > > +++ b/include/linux/device.h > > > > @@ -200,6 +200,7 @@ extern struct klist *bus_get_device_klist(struct bus_type *bus); > > > > * @owner: The module owner. > > > > * @mod_name: Used for built-in modules. > > > > * @suppress_bind_attrs: Disables bind/unbind via sysfs. > > > > + * @sysfs_bind_only: Only allow bind/unbind via sysfs. > > > > * @of_match_table: The open firmware table. > > > > * @acpi_match_table: The ACPI match table. > > > > * @probe: Called to query the existence of a specific device, > > > > @@ -233,6 +234,7 @@ struct device_driver { > > > > const char *mod_name; /* used for built-in modules */ > > > > > > > > bool suppress_bind_attrs; /* disables bind/unbind via sysfs */ > > > > + bool sysfs_bind_only; /* only allow bind/unbind via sysfs */ > > > > > > > > const struct of_device_id *of_match_table; > > > > const struct acpi_device_id *acpi_match_table; > > > > > > I think I only discussed this with Stuart in person at the KVM Forum: > > > Why not deriving the property "sysfs bind only" from the fact that a > > > device does wild-card binding? Are there use cases that benefit from > > > decoupling both features? > > > > you mean merge the two new flags sysfs_bind_only and platform driver's > > match_any_dev into one new single driver flag, right? good question. > > What would combining them solve, other than making it more likely that > Greg complains about the wildcard because it would no longer be handled > at the bus level where all the other matching goes on? > > They are logically separate things. That doesn't change just because we > currently plan to use them together. Jan? Given the above, what would be the advantage of merging sysfs_bind_only and (PCI drivers' PCI_ANY_ID and platform drivers' match_any_dev)? Kim