linux-kernel - Re: [PATCH 19/23] PCI: add /sys/bus/pci/rescan

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Date:	Tue, 6 Mar 2012 22:37:43 -0800
From:	Yinghai Lu <yinghai@...nel.org>
To:	Bjorn Helgaas <bjorn.helgaas@...il.com>
Cc:	Jesse Barnes <jbarnes@...tuousgeek.org>, x86 <x86@...nel.org>,
	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
	Randy Dunlap <rdunlap@...otime.net>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-doc@...r.kernel.org
Subject: Re: [PATCH 19/23] PCI: add /sys/bus/pci/rescan_root

On Tue, Mar 6, 2012 at 8:31 PM, Bjorn Helgaas <bjorn.helgaas@...il.com> wrote:
> On Tue, Mar 6, 2012 at 12:13 AM, Yinghai Lu <yinghai@...nel.org> wrote:
>>
>> It will be used to rediscover removed pci root buses.
>>
>> Signed-off-by: Yinghai Lu <yinghai@...nel.org>
>> Cc: Randy Dunlap <rdunlap@...otime.net>
>> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
>> Cc: linux-doc@...r.kernel.org
>> ---
>>  Documentation/ABI/testing/sysfs-bus-pci |    9 +++++++++
>>  drivers/pci/pci-sysfs.c                 |   21 +++++++++++++++++++++
>>  2 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:
>>                re-discover previously removed devices.
>>                Depends on CONFIG_HOTPLUG.
>>
>> +What:          /sys/bus/pci/rescan_root
>> +Date:          March 2012
>> +Contact:       Linux PCI developers <linux-pci@...r.kernel.org>
>> +Description:
>> +               Writing a non-zero value to this attribute will
>> +               cause a rescan of all PCI root buses in the system, and
>> +               re-discover previously removed PCI root buses.
>
> 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.
>
>> +               Depends on CONFIG_HOTPLUG.
>> +
>>  What:          /sys/bus/pci/devices/.../msi_irqs/
>>  Date:          September, 2011
>>  Contact:       Neil Horman <nhorman@...driver.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,
>>        return count;
>>  }
>>
>> +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,
>> +                               size_t count)
>> +{
>> +       unsigned long val;
>> +
>> +       if (strict_strtoul(buf, 0, &val) < 0)
>> +               return -EINVAL;
>> +
>> +       if (val) {
>> +               mutex_lock(&pci_remove_rescan_mutex);
>> +               acpi_pci_root_rescan();
>
> This architecture-dependent function name should not be here.  How
> will we make this work for powerpc, sparc, etc.?
>
>> +               pcibios_root_rescan();
>> +               mutex_unlock(&pci_remove_rescan_mutex);

how about arch_pci_root_rescan(), and for x86 will let include
arch_pci_root_rescan()
pcibios_root_rescan().

need to check arch like powerpc,  sparc  to see if could
add pcibios_root_rescan()

Yinghai
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