linux-kernel - Re: [PATCH v8 11/22] PCI: correctly detect ACPI PCI host bridge objects

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Date:	Sun, 13 Jan 2013 00:34:10 +0100
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Yinghai Lu <yinghai@...nel.org>
Cc:	Bjorn Helgaas <bhelgaas@...gle.com>, Len Brown <lenb@...nel.org>,
	Taku Izumi <izumi.taku@...fujitsu.com>,
	Jiang Liu <jiang.liu@...wei.com>, linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-acpi@...r.kernel.org
Subject: Re: [PATCH v8 11/22] PCI: correctly detect ACPI PCI host bridge objects

On Friday, January 11, 2013 02:40:38 PM Yinghai Lu wrote:
> From: Jiang Liu <jiang.liu@...wei.com>
> 
> The code in pci_root_hp.c depends on function acpi_is_root_bridge()
> to check whether an ACPI object is a PCI host bridge or not.
> If an ACPI device hasn't been created for the ACPI object yet,
> function acpi_is_root_bridge() will return false even if the object
> is a PCI host bridge object. That behavior will cause two issues:
> 1) No ACPI notification handler installed for PCI host bridges absent
>    at startup, so hotplug events for those bridges won't be handled.
> 2) rescan_root_bridge() can't reenumerate offlined PCI host bridges
>    because the ACPI devices have been already destroyed.
> 
> So use acpi_match_object_info_ids() to correctly detect PCI host bridges.
> 
> -v2: update to use acpi_match_object_info_ids() from Tang Chen  - Yinghai
> -v3: drop the PNP0A008, according to Bjorn.
> 
> Signed-off-by: Jiang Liu <jiang.liu@...wei.com>
> Signed-off-by: Yinghai Lu <yinghai@...nel.org>
> Cc: Len Brown <lenb@...nel.org>
> Cc: linux-acpi@...r.kernel.org
> ---
>  drivers/acpi/pci_root.c |   19 ++++++++++++++++++-
>  1 file changed, 18 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/acpi/pci_root.c b/drivers/acpi/pci_root.c
> index 5ae36d8..d30fb94 100644
> --- a/drivers/acpi/pci_root.c
> +++ b/drivers/acpi/pci_root.c
> @@ -923,6 +923,23 @@ static void handle_hotplug_event_root(acpi_handle handle, u32 type,
>  				_handle_hotplug_event_root);
>  }
>  
> +static bool acpi_is_root_bridge_object(acpi_handle handle)
> +{
> +	struct acpi_device_info *info = NULL;
> +	acpi_status status;
> +	bool ret;
> +
> +	status = acpi_get_object_info(handle, &info);
> +	if (ACPI_FAILURE(status))
> +		return false;
> +
> +	ret = !acpi_match_object_info_ids(info, root_device_ids);
> +

Well, I kind of don't understand why don't we check info->flags
against ACPI_PCI_ROOT_BRIDGE that acpi_get_object_info() sets for us if it
finds a PCI root bridge?

> +	kfree(info);
> +
> +	return ret;
> +}
> +
>  static acpi_status __init
>  find_root_bridges(acpi_handle handle, u32 lvl, void *context, void **rv)
>  {
> @@ -931,7 +948,7 @@ find_root_bridges(acpi_handle handle, u32 lvl, void *context, void **rv)
>  				      .pointer = objname };
>  	int *count = (int *)context;
>  
> -	if (!acpi_is_root_bridge(handle))
> +	if (!acpi_is_root_bridge_object(handle))
>  		return AE_OK;
>  
>  	(*count)++;
> 

Thanks,
Rafael


-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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