ACPI: crosslink ACPI and "real" device nodes

Add cross-links between ACPI device and "real" devices in sysfs,
exposing otherwise-hidden interrelationships between the various
device nodes for ACPI stuff.  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,
and is what a Linux device driver binds to.  The ACPI device has instead
a "physical_node" link pointing back to the PNP device.  Other firmware
frameworks, like OpenFirmware, could do the same thing to couple their
firmware tables to the rest of the system.

(Based on a patch from Zhang Rui.  This version is modified to not
depend on the patch makig ACPI initialize driver model wakeup flags.)

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Cc: Zhang Rui <rui.zhang@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>

1 files changed, 20 insertions, 0 deletions

diff --git a/drivers/acpi/glue.c b/drivers/acpi/glue.c
index eda0978b57c6..06f8634fe58b 100644
--- a/drivers/acpi/glue.c
+++ b/drivers/acpi/glue.c
@@ -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 +158,16 @@ static int acpi_bind_one(struct device *dev, acpi_handle handle)
         }
         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");
+                ret = sysfs_create_link(&acpi_dev->dev.kobj, &dev->kobj,
+                                "physical_node");
+        }
+
         return 0;
 }
 
@@ -165,8 +176,17 @@ static int acpi_unbind_one(struct device *dev)
         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;