linux-kernel - Re: [PATCH v2 24/37] PCI, ACPI: Add pci_root

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Date:	Mon, 12 Mar 2012 23:06:42 -0700
From:	Yinghai Lu <yinghai@...nel.org>
To:	Bjorn Helgaas <bhelgaas@...gle.com>
Cc:	Jesse Barnes <jbarnes@...tuousgeek.org>, x86 <x86@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
	Len Brown <lenb@...nel.org>, linux-acpi@...r.kernel.org
Subject: Re: [PATCH v2 24/37] PCI, ACPI: Add pci_root_hp hot removal
 notification support.

On Mon, Mar 12, 2012 at 8:25 PM, Bjorn Helgaas <bhelgaas@...gle.com> wrote:
> On Sat, Mar 10, 2012 at 12:00 AM, Yinghai Lu <yinghai@...nel.org> wrote:
>> Add missing hot_remove support for root device.
>>
>> How to use it?
>> Find out root bus number to acpi root name mapping from dmesg or /sys
>>
>>  echo "\_SB.PCIB 3" > /proc/acpi/sci/notify
>> to remove root bus
>
> Same comments as before: this is definitely NOT the way users should
> use this.  If you want to do that for debugging the ACPI notification
> path, fine, but the normal way is for the platform to generate this
> notification.  I think the normal way for users to manually remove an
> ACPI device should be something like:
>
>    echo 1 > /sys/devices/LNXSYSTM:00/device:00/PNP0A08:00/remove
>
> just like we do for PCI devices.

notify way looks more like really physical hotadd/remove.

pci bus/remove and other is not really, because when you are using
/sys, you may still need to hold
one reference to bus or device.

>
>> Signed-off-by: Yinghai Lu <yinghai@...nel.org>
>> Cc: Len Brown <lenb@...nel.org>
>> Cc: linux-acpi@...r.kernel.org
>> ---
>>  drivers/acpi/pci_root_hp.c |   61 ++++++++++++++++++++++++++++++++++++++++++++
>>  1 files changed, 61 insertions(+), 0 deletions(-)
>>
>> diff --git a/drivers/acpi/pci_root_hp.c b/drivers/acpi/pci_root_hp.c
>> index dc11e81..f5585f5 100644
>> --- a/drivers/acpi/pci_root_hp.c
>> +++ b/drivers/acpi/pci_root_hp.c
>> @@ -73,6 +73,12 @@ static void add_acpi_root_bridge(acpi_handle handle)
>>        list_add(&bridge->list, &acpi_root_bridge_list);
>>  }
>>
>> +static void remove_acpi_root_bridge(struct acpi_root_bridge *bridge)
>> +{
>> +       list_del(&bridge->list);
>> +       kfree(bridge);
>> +}
>> +
>>  struct acpi_root_hp_work {
>>        struct work_struct work;
>>        acpi_handle handle;
>> @@ -142,6 +148,55 @@ static void handle_root_bridge_insertion(acpi_handle handle)
>>                printk(KERN_ERR "cannot start bridge\n");
>>  }
>>
>> +static int acpi_root_evaluate_object(acpi_handle handle, char *cmd, int val)
>> +{
>> +       acpi_status status;
>> +       struct acpi_object_list arg_list;
>> +       union acpi_object arg;
>> +
>> +       arg_list.count = 1;
>> +       arg_list.pointer = &arg;
>> +       arg.type = ACPI_TYPE_INTEGER;
>> +       arg.integer.value = val;
>> +
>> +       status = acpi_evaluate_object(handle, cmd, &arg_list, NULL);
>> +       if (ACPI_FAILURE(status)) {
>> +               printk(KERN_WARNING "%s: %s to %d failed\n",
>> +                                __func__, cmd, val);
>> +               return -1;
>> +       }
>> +
>> +       return 0;
>
> This function really has nothing to do with host bridges.  Are you
> sure there's no generic function you can use instead?

seems not.
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