[PATCH v3 13/17] ACPI: identify device tree root by null parent pointer, not ACPI_BUS_TYPE

Bjorn Helgaas
2009-09-21T19:29:47Z

We can identify the root of the ACPI device tree by the fact that it
has no parent. This is simpler than passing around ACPI_BUS_TYPE_SYSTEM
and will help remove special treatment of the device tree root.

Currently, we add the root by hand with ACPI_BUS_TYPE_SYSTEM. If we
traverse the tree treating the root as just another device and use
acpi_get_type(), the root shows up as ACPI_TYPE_DEVICE.

Signed-off-by: Bjorn Helgaas <bjorn.helgaas@hp.com>
---
drivers/acpi/scan.c | 20 +++++++++++++-------
include/acpi/acpi_bus.h | 1 -
2 files changed, 13 insertions(+), 8 deletions(-)

diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
index 27d2dec..0b5aaf0 100644
--- a/drivers/acpi/scan.c
+++ b/drivers/acpi/scan.c
@@ -22,6 +22,8 @@ extern struct acpi_device *acpi_root;
#define ACPI_BUS_HID "LNXSYBUS"
#define ACPI_BUS_DEVICE_NAME "System Bus"

+#define ACPI_IS_ROOT_DEVICE(device) (!(device)->parent)
+
static LIST_HEAD(acpi_device_list);
static LIST_HEAD(acpi_bus_id_list);
DEFINE_MUTEX(acpi_device_lock);
@@ -955,10 +957,12 @@ static void acpi_device_get_busid(struct acpi_device *device)
* The device's Bus ID is simply the object name.
* TBD: Shouldn't this value be unique (within the ACPI namespace)?
*/
- switch (device->device_type) {
- case ACPI_BUS_TYPE_SYSTEM:
+ if (ACPI_IS_ROOT_DEVICE(device)) {
strcpy(device->pnp.bus_id, "ACPI");
- break;
+ return;
+ }
+
+ switch (device->device_type) {
case ACPI_BUS_TYPE_POWER_BUTTON:
strcpy(device->pnp.bus_id, "PWRF");
break;
@@ -1093,6 +1097,11 @@ static void acpi_device_set_id(struct acpi_device *device)

switch (device->device_type) {
case ACPI_BUS_TYPE_DEVICE:
+ if (ACPI_IS_ROOT_DEVICE(device)) {
+ hid = ACPI_SYSTEM_HID;
+ break;
+ }
+
status = acpi_get_object_info(device->handle, &info);
if (ACPI_FAILURE(status)) {
printk(KERN_ERR PREFIX "%s: Error reading device info\n", __func__);
@@ -1129,9 +1138,6 @@ static void acpi_device_set_id(struct acpi_device *device)
case ACPI_BUS_TYPE_PROCESSOR:
hid = ACPI_PROCESSOR_OBJECT_HID;
break;
- case ACPI_BUS_TYPE_SYSTEM:
- hid = ACPI_SYSTEM_HID;
- break;
case ACPI_BUS_TYPE_THERMAL:
hid = ACPI_THERMAL_HID;
break;
@@ -1643,7 +1649,7 @@ int __init acpi_scan_init(void)
* Create the root device in the bus's device tree
*/
result = acpi_add_single_object(&acpi_root, ACPI_ROOT_OBJECT,
- ACPI_BUS_TYPE_SYSTEM, &ops);
+ ACPI_BUS_TYPE_DEVICE, &ops);
if (result)
goto Done;

diff --git a/include/acpi/acpi_bus.h b/include/acpi/acpi_bus.h
index 8e39b3e..ef1cb23 100644
--- a/include/acpi/acpi_bus.h
+++ b/include/acpi/acpi_bus.h
@@ -70,7 +70,6 @@ enum acpi_bus_device_type {
ACPI_BUS_TYPE_POWER,
ACPI_BUS_TYPE_PROCESSOR,
ACPI_BUS_TYPE_THERMAL,
- ACPI_BUS_TYPE_SYSTEM,
ACPI_BUS_TYPE_POWER_BUTTON,
ACPI_BUS_TYPE_SLEEP_BUTTON,
ACPI_BUS_DEVICE_TYPE_COUNT