Re: [patch 2.6.25-rc6 1/7] crosslink ACPI and "real" device nodes

[Zhao Yakui <yakui.zhao@intel.com>]

On Thu, 2008-03-20 at 14:09 -0700, David Brownell wrote:
> From: David Brownell <dbrownell@users.sourceforge.net>
> 
> Add cross-links between ACPI device and "real" devices in sysfs,
> exposing otherwise-hidden interrelationships between the various
> device nodes which ACPI creates.  As a representative example one
> hardware device is exposed as two logical devices (PNP and ACPI):
> 
>   .../pnp0/00:06/
>   .../LNXSYSTM:00/device:00/PNP0A03:00/device:15/PNP0B00:00/
> 
> The PNP device gets a "firmware_node" link pointing to the ACPI device.
> The ACPI device has a "physical_node" link pointing to the PNP device.
> Linux drivers currently bind only to the "physical" device nodes.
Very good idea. 
But maybe there is a lot of ACPI devices on the laptops. And we take a
little care about the association between the acpi device and "real"
device.
Maybe it is more useful if the link is set up for the acpi device with
the _PRW object. Maybe the link that points to ACPI device with the _PRW
object is created in the /sys/power/.
> 
> Other device trees provided by firmware tables could be exported
> using the same scheme; these names aren't ACPI-specific.
> 
> (Based on a patch from Zhang Rui.  This version is modified to not
> depend on the patch teaching ACPI about driver model wakeup flags.)
> Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
> Cc: Zhang Rui <rui.zhang@intel.com> 
> ---
> Change from previous version:  if creating the link fails, a
> pr_debug level message is emitted.
> 
>  drivers/acpi/glue.c |   27 +++++++++++++++++++++++++++
>  1 file changed, 27 insertions(+)
> 
> --- g26.orig/drivers/acpi/glue.c	2008-03-08 11:11:18.000000000 -0800
> +++ g26/drivers/acpi/glue.c	2008-03-08 11:29:07.000000000 -0800
> @@ -142,6 +142,7 @@ EXPORT_SYMBOL(acpi_get_physical_device);
>  
>  static int acpi_bind_one(struct device *dev, acpi_handle handle)
>  {
> +	struct acpi_device *acpi_dev;
>  	acpi_status status;
>  
>  	if (dev->archdata.acpi_handle) {
> @@ -157,6 +158,23 @@ static int acpi_bind_one(struct device *
>  	}
>  	dev->archdata.acpi_handle = handle;
>  
> +	status = acpi_bus_get_device(handle, &acpi_dev);
> +	if (!ACPI_FAILURE(status)) {
> +		int ret;
> +
> +		ret = sysfs_create_link(&dev->kobj, &acpi_dev->dev.kobj,
> +				"firmware_node");
> +		if (ret != 0)
> +			pr_debug(PREFIX "Can't create %s link for %s\n",
> +				"firmware_node", dev->bus_id);
> +
> +		ret = sysfs_create_link(&acpi_dev->dev.kobj, &dev->kobj,
> +				"physical_node");
> +		if (ret != 0)
> +			pr_debug(PREFIX "Can't create %s link for %s\n",
> +				"physical_node", acpi_dev->dev.bus_id);
> +	}
> +
>  	return 0;
>  }
>  
> @@ -165,8 +183,17 @@ static int acpi_unbind_one(struct device
>  	if (!dev->archdata.acpi_handle)
>  		return 0;
>  	if (dev == acpi_get_physical_device(dev->archdata.acpi_handle)) {
> +		struct acpi_device *acpi_dev;
> +
>  		/* acpi_get_physical_device increase refcnt by one */
>  		put_device(dev);
> +
> +		if (!acpi_bus_get_device(dev->archdata.acpi_handle,
> +					&acpi_dev)) {
> +			sysfs_remove_link(&dev->kobj, "firmware_node");
> +			sysfs_remove_link(&acpi_dev->dev.kobj, "physical_node");
> +		}
> +
>  		acpi_detach_data(dev->archdata.acpi_handle,
>  				 acpi_glue_data_handler);
>  		dev->archdata.acpi_handle = NULL;
> --
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