linux-kernel - Re: [PATCH 2/3 v2] Do not use acpi_device to find pci root bridge in

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Date:	Fri, 12 Oct 2012 11:32:10 -0700
From:	Yinghai Lu <yinghai@...nel.org>
To:	Tang Chen <tangchen@...fujitsu.com>
Cc:	bhelgaas@...gle.com, lenb@...nel.org, jiang.liu@...wei.com,
	izumi.taku@...fujitsu.com, isimatu.yasuaki@...fujitsu.com,
	linux-acpi@...r.kernel.org, linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3 v2] Do not use acpi_device to find pci root bridge in
 _init code.

On Fri, Oct 12, 2012 at 5:34 AM, Tang Chen <tangchen@...fujitsu.com> wrote:
> When the kernel is being initialized, and some hardwares are not added
> to system, there won't be acpi_device structs for these devices. But
> acpi_is_root_bridge() depends on acpi_device struct. As a result, all
> the not-added root bridge will not be judged as a root bridge in
> find_root_bridges(). And further more, no handle_hotplug_event_root()
> notifier will be installed for them.
>
> This patch introduces a new api to find all root bridges in system by
> getting HID directly from ACPI namespace, not depending on acpi_device
> struct.
>
> Signed-off-by: Tang Chen <tangchen@...fujitsu.com>
> Signed-off-by: Liu Jiang <jiang.liu@...wei.com>
> ---
>  drivers/acpi/pci_root.c |   19 +++++++++++--------
>  1 files changed, 11 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/acpi/pci_root.c b/drivers/acpi/pci_root.c
> index 6151d83..582eb11 100644
> --- a/drivers/acpi/pci_root.c
> +++ b/drivers/acpi/pci_root.c
> @@ -129,20 +129,23 @@ EXPORT_SYMBOL_GPL(acpi_get_pci_rootbridge_handle);
>   * acpi_is_root_bridge - determine whether an ACPI CA node is a PCI root bridge
>   * @handle - the ACPI CA node in question.
>   *
> - * Note: we could make this API take a struct acpi_device * instead, but
> - * for now, it's more convenient to operate on an acpi_handle.
> + * Note: If a device is not added to the system yet, there won't be an
> + * acpi_device struct for it. So do not get HID and CID from acpi_device,
> + * get them from ACPI namespace directly.
>   */
>  int acpi_is_root_bridge(acpi_handle handle)
>  {
> -       int ret;
> -       struct acpi_device *device;
> +       struct acpi_device_info *info;
> +       acpi_status status;
>
> -       ret = acpi_bus_get_device(handle, &device);
> -       if (ret)
> +       status = acpi_get_object_info(handle, &info);
> +       if (ACPI_FAILURE(status)) {
> +               printk(KERN_ERR PREFIX "%s: Error reading"
> +                                      "device info\n", __func__);
>                 return 0;
> +       }
>
> -       ret = acpi_match_device_ids(device, root_device_ids);
> -       if (ret)
> +       if (acpi_match_object_info_ids(info, root_device_ids))
>                 return 0;
>         else
>                 return 1;

there are some other users for acpi_is_root_bridge.

drivers/acpi/pci_root.c:        while (!acpi_is_root_bridge(phandle)) {
drivers/pci/hotplug/acpi_pcihp.c:               if (acpi_is_root_bridge(handle))
drivers/pci/hotplug/acpi_pcihp.c:               if (acpi_is_root_bridge(handle))

and they are ok to have acpi_device ready.

so we could have another separated static version for those not added ones?

Thanks

Yinghai
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