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SubjectRe: [PATCH 1/6] ACPI: Separate adding ACPI device objects from probing ACPI drivers
On 12/10/2012 07:00 AM, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
>
> Currently, as soon as an ACPI device node object (struct acpi_device)
> is created, the driver core attempts to probe ACPI drivers against
> it. That leads to some unpleasant side effects, like the fact that
> the boot code path for ACPI namespace scanning is different from the
> analogous hot-plug code path (during boot ACPI drivers are not
> present when ACPI device node objects are registered, so they are
> guaranteed not to be probed, which is not the case during hot-plug).
> That, in turn, leads to unnecessary complications in the PCI
> enumeration algorithm.
>
> Reduce the differences between the boot and hot-plug cases by
> splitting the ACPI namespace scanning for devices into two passes,
> such that struct acpi_device objects are registerd in the first
> patch without probing ACPI drivers and the drivers are probed
> against them directly in the second pass. This way ACPI drivers
> can assume that all of the ACPI device node objects in the given
> scope will be registered when their .add() routines run and the
> hot-plug case becomes the same as the boot case from their
> perspective.
>
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> ---
> drivers/acpi/scan.c | 96 +++++++++++++++++++++++++++++++++---------------
> include/acpi/acpi_bus.h | 1
> 2 files changed, 68 insertions(+), 29 deletions(-)
>
> Index: linux/include/acpi/acpi_bus.h
> ===================================================================
> --- linux.orig/include/acpi/acpi_bus.h
> +++ linux/include/acpi/acpi_bus.h
> @@ -98,6 +98,7 @@ typedef void (*acpi_op_notify) (struct a
> struct acpi_bus_ops {
> u32 acpi_op_add:1;
> u32 acpi_op_start:1;
> + u32 acpi_op_match:1;
> };
>
> struct acpi_device_ops {
> Index: linux/drivers/acpi/scan.c
> ===================================================================
> --- linux.orig/drivers/acpi/scan.c
> +++ linux/drivers/acpi/scan.c
> @@ -494,7 +494,8 @@ static int acpi_bus_match(struct device
> struct acpi_device *acpi_dev = to_acpi_device(dev);
> struct acpi_driver *acpi_drv = to_acpi_driver(drv);
>
> - return !acpi_match_device_ids(acpi_dev, acpi_drv->ids);
> + return acpi_dev->bus_ops.acpi_op_match
> + && !acpi_match_device_ids(acpi_dev, acpi_drv->ids);
> }
Hi Rafael,
PCI host bridge hotplug has the same requirement to separate device
enumeration from device driver binding. And VFIO has a similar requirement too.
Yinghai and I have implemented two different solutions for PCI host bridge
hotplug but all rejected by Greg. So it would be great if we could promote
a common mechanism to the device core to temporarily disable binding drivers
to devices, which could used to support ACPI hotplug, PCI hotplug and VFIO.
Regards!
Gerry



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