[patch 2.6.25-rc2-git] crosslink ACPI and "real" device nodes

David Brownell
2008-02-23T05:54:24Z

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>
---
Another extract from the "teach ACPI how to use driver model wakeup
flags" patch series. The linkage helps sort out confusion about which
devices are wakeup-capable, among other things, and can help when
interpreting /proc/acpi/wakeup contents.

drivers/acpi/glue.c | 20 ++++++++++++++++++++
1 file changed, 20 insertions(+)

--- g26.orig/drivers/acpi/glue.c 2008-02-22 20:39:19.000000000 -0800
+++ g26/drivers/acpi/glue.c 2008-02-22 20:46:40.000000000 -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 +158,16 @@ 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");
+ 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
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;