Re: [PATCH 19/23] PCI: add /sys/bus/pci/rescan_root

[Bjorn Helgaas <bjorn.helgaas@gmail.com>]

On Tue, Mar 6, 2012 at 12:13 AM, Yinghai Lu <yinghai@kernel.org> wrote:
>
> It will be used to rediscover removed pci root buses.
>
> Signed-off-by: Yinghai Lu <yinghai@kernel.org>
> Cc: Randy Dunlap <rdunlap@xenotime.net>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Cc: linux-doc@vger.kernel.org
> ---
> =A0Documentation/ABI/testing/sysfs-bus-pci | =A0 =A09 +++++++++
> =A0drivers/pci/pci-sysfs.c =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 | =A0 21 +++++=
++++++++++++++++
> =A02 files changed, 30 insertions(+), 0 deletions(-)
>
> diff --git a/Documentation/ABI/testing/sysfs-bus-pci
> b/Documentation/ABI/testing/sysfs-bus-pci
> index 22392de..eb826bd 100644
> --- a/Documentation/ABI/testing/sysfs-bus-pci
> +++ b/Documentation/ABI/testing/sysfs-bus-pci
> @@ -66,6 +66,15 @@ Description:
> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0re-discover previously removed devices.
> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0Depends on CONFIG_HOTPLUG.
>
> +What: =A0 =A0 =A0 =A0 =A0/sys/bus/pci/rescan_root
> +Date: =A0 =A0 =A0 =A0 =A0March 2012
> +Contact: =A0 =A0 =A0 Linux PCI developers <linux-pci@vger.kernel.org>
> +Description:
> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 Writing a non-zero value to this attribute =
will
> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 cause a rescan of all PCI root buses in the=
 system, and
> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 re-discover previously removed PCI root bus=
es.

This seems sort of backwards to me.  Architecture-specific code
enumerated the host bridges/root buses in the first place, not the PCI
core.  Now we're asking the PCI core (/sys/bus/pci) to re-enumerate
them.

But maybe it's still the right answer, I dunno.

> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 Depends on CONFIG_HOTPLUG.
> +
> =A0What: =A0 =A0 =A0 =A0 =A0/sys/bus/pci/devices/.../msi_irqs/
> =A0Date: =A0 =A0 =A0 =A0 =A0September, 2011
> =A0Contact: =A0 =A0 =A0 Neil Horman <nhorman@tuxdriver.com>
> diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
> index f855b4b..d6221e5 100644
> --- a/drivers/pci/pci-sysfs.c
> +++ b/drivers/pci/pci-sysfs.c
> @@ -302,8 +302,29 @@ static ssize_t bus_rescan_store(struct bus_type *bus=
,
> const char *buf,
> =A0 =A0 =A0 =A0return count;
> =A0}
>
> +void __weak acpi_pci_root_rescan(void) { }
> +void __weak pcibios_root_rescan(void) { }
> +
> +static ssize_t bus_rescan_root_store(struct bus_type *bus, const char
> *buf,
> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 size_t coun=
t)
> +{
> + =A0 =A0 =A0 unsigned long val;
> +
> + =A0 =A0 =A0 if (strict_strtoul(buf, 0, &val) < 0)
> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 return -EINVAL;
> +
> + =A0 =A0 =A0 if (val) {
> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 mutex_lock(&pci_remove_rescan_mutex);
> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 acpi_pci_root_rescan();

This architecture-dependent function name should not be here.  How
will we make this work for powerpc, sparc, etc.?

> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 pcibios_root_rescan();
> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 mutex_unlock(&pci_remove_rescan_mutex);
> + =A0 =A0 =A0 }
> + =A0 =A0 =A0 return count;
> +}
> +
> =A0struct bus_attribute pci_bus_attrs[] =3D {
> =A0 =A0 =A0 =A0__ATTR(rescan, (S_IWUSR|S_IWGRP), NULL, bus_rescan_store),
> + =A0 =A0 =A0 __ATTR(rescan_root, (S_IWUSR|S_IWGRP), NULL,
> bus_rescan_root_store),
> =A0 =A0 =A0 =A0__ATTR_NULL
> =A0};
>
> --
> 1.7.7
>
> --
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