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SubjectRe: [REPOST][PATCH 1/2] driver core: Add new device_driver flag to allow binding via sysfs only
On Tue, Dec 03, 2013 at 04:34:33PM +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 <stuart.yoder@freescale.com>
> > Signed-off-by: Kim Phillips <kim.phillips@linaro.org>
> > ---
> > 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?

The driver core does not know if a bus, or a device, handles "wild card"
binding, so you can't do it at this level, sorry.

greg k-h


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