Re: [PATCH 2/3] Do not use acpi_device to find pci root bridge in _init code.

[Jiang Liu <jiang.liu@huawei.com>]

On 2012-10-12 18:31, Tang Chen 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@cn.fujitsu.com>
> ---
>  drivers/acpi/pci_root.c |   27 ++++++++++++++++++++++-----
>  1 files changed, 22 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/acpi/pci_root.c b/drivers/acpi/pci_root.c
> index 7d0fb03..3819bee 100644
> --- a/drivers/acpi/pci_root.c
> +++ b/drivers/acpi/pci_root.c
> @@ -128,9 +128,6 @@ 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.
>   */
>  int acpi_is_root_bridge(acpi_handle handle)
>  {
> @@ -138,8 +135,28 @@ int acpi_is_root_bridge(acpi_handle handle)
>  	struct acpi_device *device;
>  
>  	ret = acpi_bus_get_device(handle, &device);
> -	if (ret)
> -		return 0;
> +	if (ret) {
> +		/**
> +		 * If a device is not added to the system yet, there won't be
> +		 * an acpi_device struct for it. But it doesn't mean it is not
> +		 * a PCI root bridge. In this case we need to get HID and CID
> +		 * from ACPI namespace directly.
> +		 */
> +		struct acpi_device_info *info;
> +		acpi_status status;
> +		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_object_info_ids(info, root_device_ids);
> +		if (ret)
> +			return 0;
> +		else
> +			return 1;
> +	}
I have sent a similar patch to Yinghai before. For simplicity, we could
use acpi_match_object_info_ids() instead of acpi_match_device_ids()
directly.
Thanks!
Gerry

>  
>  	ret = acpi_match_device_ids(device, root_device_ids);
>  	if (ret)